Atypical Lipomatous Tumor/well-differentiated Liposarcoma Research Articles

An overview on liposarcoma subtypes: Genetic alterations and recent advances in therapeutic strategies.

Liposarcoma (LPS) is a rare malignancy of adipocytic differentiation. According to World Health Organization classification, LPS comprises of four principle subtypes Atypical lipomatous tumor/Well-differentiated liposarcoma (ATL/WDLPS), Dedifferentiated liposarcoma (WDLPS), Myxoid liposarcoma (MLPS), and Pleomorphic liposarcoma (PLPS). Each subtype can develop at any location and shows distinct clinical behavior and treatment sensitivity. ATL/ WDLPS subtype has a higher incidence rate, low recurrence, and is insensitive to radiation and chemotherapy. DDLPS is the focal progression of WDLPS, which is aggressive and highly metastasizing. MLPS is sensitive to radiation and chemotherapy, with a higher recurrence rate and metastasis. PLPS subtype is highly metastasizing, has a poor prognosis, and exhibiting higher recurrence rate. Initial histological analysis provides information for the characterization of LPS subtypes', further molecular and genetic analysis provides certain subtype specifications, such as gene amplifications and gene fusions. Such molecular genetic alterations will be useful as therapeutic targets in various cancers, including the LPS subtypes. A wide range of novel therapeutic agents based on genetic alterations that aim to target LPS subtypes specifically are under investigation. This review summarizes the LPS subtype classification, their molecular genetic characteristics, and the implications of genetic alterations in therapeutics.

Superficial dedifferentiated liposarcoma: A clinicopathologic study

IntroductionDedifferentiation occurs in approximately 10% of atypical lipomatous tumors/well-differentiated liposarcomas (ALT/WDLPS), primarily in retroperitoneal or deep-seated tumors, conferring metastatic potential. Superficial dedifferentiated liposarcoma (sDDLPS) is rare, and its progression and natural history are poorly documented. MethodsWe performed a 15-year retrospective review of our pathology database to identify cases of DDLPS in the skin or subcutaneous tissue. Diagnosis of primary sDDLPS required evidence of non-lipogenic sarcoma in the skin or subcutis, with concurrent ALT/WDLPS and/or MDM2 amplification. ResultsWe identified 14 cases of DDLPS involving skin or subcutis: 7 primary sDDLPS and 7 secondary lesions (3 from recurrent deep DDLPS and 4 from metastasis). Primary sDDLPS cases (4 females, 3 males; median age: 74) mainly presented as undifferentiated spindle cell or pleomorphic sarcoma. Tumor grades were grade 2 (5 cases) and grade 3 (2 cases), with three cases also showing grade 1 areas. MDM2 amplification was confirmed in 6 sDDLPSs for which FISH was successfully performed. Follow-up available for 6 sDDLPS patients showed 2 local recurrences, treated with re-excision and radiation therapy, with all disease-free at last follow-up (5–126 months). Of the 7 secondary cases, 2 had ongoing disease after multiple recurrences, 1 was disease-free, and all 4 with cutaneous metastasis died of disease (follow-up range: 24–263 months). ConclusionThese findings emphasize the importance of distinguishing between primary sDDLPS and secondary lesions due to their distinct prognoses. Metastasis or superficial extensions from deep DDLP correlate with a considerably worse prognosis than those originating in superficial tissues.

A Large Atypical Lipomatous Tumor/Well-Differentiated Liposarcoma of Buccal Mucosa: Report of A Rare Case

Abstract Introduction/Objective Liposarcoma is not common in the head and neck, and extremely rare in the oral cavity: 7% occur in the head and neck and 0.3% in the oral cavity. We report an atypical lipomatous tumor/well-differentiated liposarcoma (ATL/WDL) of the buccal mucosa with recurrence. Methods/Case Report A 66-year-old female presented with a right facial mass that had been present for over 10 years and resected 6 times as lipoma in her home country. The mass had grown since the last resection two years ago. Computerized tomography of neck soft tissue displayed a heterogeneous 11 cm mass with fat density in the right buccal mucosal spaces, and a 4.8 cm connecting solid nodule in the right pharyngeal mucosal space. Complete resection of the mass/nodule was performed. Grossly, the specimen consisted of two nodular masses (separately cut during operation), 13.1 cm and 7 cm, respectively. The cut surfaces of the masses revealed yellow fatty tissue with focal fleshy areas corresponding to the nodule with solid density by imagining. Microscopically, the squamous mucosa had a lipomatous tumor composed of sheets of well-differentiated adipocytes that infiltrated the underlying and surrounding skeletal muscle and connective tissue. Upon extensive sampling, scattered lipoblasts were found in relatively cellular areas. The nonlipogenic stromal cells with nuclear pleomorphism were seen in the fibrous/solid areas. No mitosis or necrosis was identified. MDM2 amplification was detected by fluorescent in situ hybridization (FISH). These findings support the diagnosis of recurrent ATL/WDL. Results (if a Case Study enter NA) NA Conclusion We demonstrate the histological features of a large atypical lipomatous tumor/well-differentiated liposarcoma of buccal mucosa. Extensive sampling of the specimen to identify the lipoblasts and atypical stromal cells, and MDM2 FISH study on suspicious cases are the keys to achieve accurate diagnosis. The high recurrence rate of this entity in the head & neck region exhibited in this case warrants the need of long-term follow-up.

Tumor-to-bone distance and radiomic features on MRI distinguish intramuscular lipomas from well-differentiated liposarcomas

BackgroundTo develop a machine learning model based on tumor-to-bone distance and radiomic features derived from preoperative MRI images to distinguish intramuscular (IM) lipomas and atypical lipomatous tumors/well-differentiated liposarcomas (ALTs/WDLSs) and compared with radiologists.MethodsThe study included patients with IM lipomas and ALTs/WDLSs diagnosed between 2010 and 2022, and with MRI scans (sequence/field strength: T1-weighted (T1W) imaging at 1.5 or 3.0 Tesla MRI). Manual segmentation of tumors based on the three-dimensional T1W images was performed by two observers to appraise the intra- and interobserver variability. After radiomic features and tumor-to-bone distance were extracted, it was used to train a machine learning model to distinguish IM lipomas and ALTs/WDLSs. Both feature selection and classification steps were performed using Least Absolute Shrinkage and Selection Operator logistic regression. The performance of the classification model was assessed using a tenfold cross-validation strategy and subsequently evaluated using the receiver operating characteristic curve (ROC) analysis. The classification agreement of two experienced musculoskeletal (MSK) radiologists was assessed using the kappa statistics. The diagnosis accuracy of each radiologist was evaluated using the final pathological results as the gold standard. Additionally, we compared the performance of the model and two radiologists in terms of the area under the receiver operator characteristic curves (AUCs) using the Delong’s test.ResultsThere were 68 tumors (38 IM lipomas and 30 ALTs/WDLSs). The AUC of the machine learning model was 0.88 [95% CI 0.72–1] (sensitivity, 91.6%; specificity, 85.7%; and accuracy, 89.0%). For Radiologist 1, the AUC was 0.94 [95% CI 0.87–1] (sensitivity, 97.4%; specificity, 90.9%; and accuracy, 95.0%), and as to Radiologist 2, the AUC was 0.91 [95% CI 0.83–0.99] (sensitivity, 100%; specificity, 81.8%; and accuracy, 93.3%). The classification agreement of the radiologists was 0.89 of kappa value (95% CI 0.76–1). Although the AUC of the model was lower than of two experienced MSK radiologists, there was no statistically significant difference between the model and two radiologists (all P > 0.05).ConclusionsThe novel machine learning model based on tumor-to-bone distance and radiomic features is a noninvasive procedure that has the potential for distinguishing IM lipomas from ALTs/WDLSs. The predictive features that suggested malignancy were size, shape, depth, texture, histogram, and tumor-to-bone distance.

Histopathological Correlation of Chromosome 12 Polysomy by Fluorescence in Situ Hybridization in Adipocytic Neoplasms

Background: Identification of MDM2 amplification by fluorescence in situ hybridization is an important diagnostic tool for evaluation of adipocytic neoplasms. Rarely, neoplasms can show increased copies of MDM2 and CEP12 probes (polysomy) without amplification (MDM2/CEP12 ratio <2.0). While noted in the literature, this finding has not been the focus of any study to date. Methods: Consecutive cases were retrospectively screened for increased copies of MDM2 and CEP12 and were classified as: high polysomy (ratio<2.0, CEP12≥10.0), low polysomy (ratio<2.0, but >0.5, CEP12≥4.0 but <9.9), and CEP12 amplification (ratio≤0.5, CEP12 > 4.0). H&E slides were classified by a pathologist into diagnostic categories based on morphology without knowledge of MDM2 amplification result. Correlations between chromosome 12 polysomy and histological features in the same region of the tumor were investigated. Results: There were 19 (0.7%) high polysomy, 52 (2.0%) low polysomy and 3 (0.1%) CEP12 amplification cases identified in the 2541 cases screened. While low polysomy was seen across benign and malignant adipocytic tumors and other sarcomas, high level polysomy was primarily seen in liposarcomas, both atypical lipomatous tumor/well-differentiated liposarcoma (ALT/WDLPS) and dedifferentiated liposarcoma (DDLPS). No lipomas were high polysomy. Conclusion: Polysomy is an uncommon, but distinct, finding in adipocytic neoplasms found across the spectrum of benign to malignant with little insight into the pathophysiology or prognosis. While low polysomy is also observed in benign adipocytic neoplasms, high polysomy is almost always seen in malignant adipocytic neoplasms and is uncommon in benign adipocytic neoplasms.

Diagnostic value of MDM2 RNA in situ hybridization in atypical lipomatous tumor/well-differentiated liposarcoma and dedifferentiated liposarcoma

Objective: To investigate the value of MDM2 RNA in situ hybridization (RNA-ISH) in diagnosing atypical lipomatous tumor/well-differentiated liposarcoma (ALT/WDL) and dedifferentiated liposarcoma (DDL). Methods: A total of 26 ALT/WDL/DDLs diagnosed from March 2017 to May 2019 in West China Hospital, Sichuan University, Chengdu, China and 18 control cases were included. MDM2 RNA-ISH was performed on all samples and compared with the fluorescence in situ hybridization (FISH) and immunohistochemistry (IHC) regarding their performance in detecting MDM2. Results: All samples were detected successfully using the three methods. Among 26 ALT/WDL/DDLs, all cases showed MDM2 amplification and positivity for MDM2 RNA-ISH (26/26, 100%). Twenty-four (24/26, 92.3%) of the 26 tested cases were positive for MDM2 IHC while two of them were negative. Eighteen control cases were all negative for MDM2 FISH and RNA-ISH, and 15 (15/18) cases were negative for MDM2 IHC. The sensitivity and specificity of RNA-ISH were both 100%, and those of MDM2 IHC were 92.3% and 83.3%, respectively. Diffuse staining was identified in all MDM2 RNA-ISH positive ALT/WDL/DDLs, but identified in only 8/24 (33.3%) of the MDM2 IHC positive cases. Among the 11 ALT/WDL/DDL samples evaluated on tissue microarray, the positive rate of MDM2 RNA-ISH was 100% with diffuse staining in all cases. The positive rate of MDM2 IHC was 9/11 while only 1 of the 9 cases showed diffuse staining. The result of MDM2 RNA-ISH was identical to that of MDM2 FISH and was overall consistent with that of MDM2 IHC (Kappa=0.763, P<0.001). Conclusions: In ALT/WDL/DDLs, results of MDM2 RNA-ISH are highly consistent with those of FISH. MDM2 RNA-ISH is more sensitive and more specific and has more diffuse positive signals than the IHC. The findings indicate that MDM2 RNA-ISH is highly valuable for the diagnosis and differential diagnosis of ALT/WDL/DDLs.

Immunohistochemical Expression of MDM2 and p16 in Adipocytic Neoplasms Measuring Ten Centimeters or more in Diameter among Filipino Patients in a Public Tertiary Hospital from 2017 to 2019

Introduction: A size of more than 10 cm suggests that a soft tissue tumor might be malignant. Pertinent ancillary diagnostic testing, such as immunohistochemistry (IHC) and fluorescence in situ hybridization (FISH), may be done to confirm the diagnosis. Several studies have shown that size may be a useful criterion in determining which tumors are candidates for further molecular testing. MDM2 and p16 are IHC markers for atypical lipomatous tumor/well-differentiated liposarcoma (ALT/WDLPS).&nbsp; Objectives: The primary objective of this study is to determine the proportion of tumors signed out as “lipomas” from 2017 to 2019, and measuring at least 10 cm, that express MDM2 and p16 on IHC and warrant revision as ALT/WDLPS. Methodology: This is a descriptive, retrospective cohort study in which all lipomas from 2017 to 2019 that measured at least 10 cm were included. The size, age of the patient, and location of each tumor were documented. The slides of all eligible cases were reviewed and immunohistochemically stained for MDM2 and p16. For each case, the intensity and immunoreactivity of each stain were assessed using a modified, four-tier scoring system. Fisher’s exact test was used to determine if a significant number of tumors expressed MDM2 or p16. Results: Thirty (30) cases satisfied the inclusion and exclusion criteria. The average size of these tumors is 15.10 cm. There is no sex predilection. The most common location of these tumors is the extremities. None of the tumors expressed MDM2, and only one case was p16-positive. The case positive for p16 also showed cytologic atypia and variability in cell size, resulting in the revision of its diagnosis from lipoma to atypical lipomatous tumor. The rate of diagnosis revision after slide review and IHC studies is 3.33%. Conclusion: None of the adipocytic tumors that measured at least 10 cm in diameter and were signed out as lipomas was MDM2 positive, and only one case was p16-positive. Thus, morphology remains the cornerstone in the diagnosis of adipocytic tumors. Careful microscopic evaluation is necessary to establish the diagnosis of malignancy in these tumors. Ancillary tests should only be considered in cases where the pathologic features are equivocal.

CD10 (neprilysin) expression: a potential adjunct in the distinction of hibernoma from morphologic mimics

Although the morphologic diagnosis of hibernoma is usually straightforward, some hibernomas have atypical morphologic features, mimicking atypical lipomatous tumors/well-differentiated liposarcomas (ALT/WDLs). In addition, the multivacuolated brown fat cells may be mistaken for lipoblasts by pathologists, especially those without significant soft tissue tumor exposure. Thus, we continue to receive in consultation cases of hibernoma sent for MDM2 fluorescence in situ hybridizationtestingto exclude ALT/WDL. Testing hibernomas for MDM2 amplification, however, adds cost and delays the final diagnosis. Recently, we have noted expression of neprilysin (CD10, CALLA), a zinc-dependent metalloproteinase involved in the inactivation of various peptide hormones, in brown fat cells, and wished to explore the potential utility of this widely available, inexpensive ancillary test in the differential diagnosis of hibernoma. Formalin-fixed, paraffin-embedded tissue sections from well-characterized cases of hibernoma (n=48), brown fat (n=21), ALTs/WDLs (n=17), pleomorphic liposarcomas (PLPSs) (n=6), lipomas (n=5), and fat necrosis (n=5) were immunostained for CD10, using a commercially available antibody and routine laboratory protocols. CD10 expression was evaluated in both adipocytes and in surrounding stromal cells. The hibernomas occurred in 28 men and 20 women, ranging from 11 to 76 years of age and involved the extremities (n=25), pelvis (n=7), abdomen/pelvis/retroperitoneum (n=7), head and neck region (n=6), back (n=2), and chest (n=1). All showed diffuse, strong CD10 expression in multivacuolated brown fat cells and in the majority of adjacent univacuolated fat cells. Brown adipose tissue from various anatomic structures showed an identical pattern of immunoreactivity. In contrast, CD10 expression was present in the adipocytes of only 3 of 17 (18%) ALTs/WDLs and was absent in lipomas and fat necrosis. Lipoblasts expressed CD10 in 3 PLPSs. Expression of CD10 by surrounding fibroblastic stromal cells was more widespread, present in 13 hibernomas, 10 ALTs/WDLs, 1 instance of fat necrosis, 6 PLPSs, and 4 examples of brown fat. We conclude that immunohistochemistry for CD10 may represent a useful, rapid and inexpensive ancillary test in the differential diagnosis of hibernoma from potential morphologic mimics, especially when morphologic features favor hibernoma. CD10 expression in adipocytes, however, should be rigorously distinguished from fibroblastic stromal cell CD10 expression, a nonspecific finding.

Nuclear expression of MDM2 in hibernoma: a potential diagnostic pitfall.

Hibernoma is a rare benign adipocytic tumor composed of a proliferation of brown and white fat cells varying in their proportions. The tumor may also contain fat cells resembling lipoblasts, which makes it difficult to distinguish it from atypical lipomatous tumor/well differentiated liposarcoma (ALT/WDLS). Although nuclear expressions of murine double minute 2 (MDM2) and cyclin-dependent kinase 4 (CDK4) are widely used as immunohistochemical surrogate markers for ALT/WDLS, the utility of these proteins in distinguishing between hibernoma and ALT/WDLS still remains to be elucidated. We evaluated immunohistochemical expressions of MDM2 and CDK4 in 10 hibernomas expressing uncoupling protein-1 (UCP-1), a mitochondrial protein transporter consistently expressed in brown fat cells, and lacking MDM2 gene amplification, which was analyzed by fluorescence in situ hybridization (FISH). In contrast to the data previously obtained, nuclear expression of MDM2 was observed in 100% (10/10 cases) of the hibernomas irrespective of the proportion of brown fat cells, whereas no cases were positive for CDK4. The tumors also showed almost concurrent expression of p53 (in 9/10 cases) and ubiquitin-specific-processing protease 7 (USP7) (in 10/10 cases), which deubiquitinates and stabilizes MDM2, potentially resulting in its nuclear expression without MDM2 gene amplification. MDM2 expression may thus be a diagnostic pitfall for hibernoma particularly in differentiating it from ALT/WDLS.

Diagnostic importance of clinicopathologic features and p16, CD34, MDM2 expression in differential diagnosis of adipocytic tumors.

The aim of this study was to investigate the immunohistochemical stain profiling of adipocytic tumors. From our archive files between the years of 2012-2018, excised, formalin-fixed and paraffin-embedded adipocytic tumors were retrospectively screened and 61 subjects were selected. The gender, age, tumor location and tumor diameter were evaluated. The cases were investigated in terms of p16, CD34, MDM2 expression and clinicopathological information. Of the 61 patients included in the study, we found that 2 had hibernoma, 4 had lipoblastoma, 14 had spindle cell lipoma (SCL), 10 had lipoma, 20 had atypical lipomatous tumor/well differentiated liposarcoma (ALT/WDL), and 11 had dedifferentiated liposarcoma (DDL). In terms of diameter, ALT/WDL and DDL were significantly different from the others (p=0.001, p=0.001, respectively). There was a significant difference between the groups according to the location (p=0.001). 35% (7/20) of ALT/WDLs were in the lower extremities (thighs) and 35% (7/20) were located in the retroperitoneal region. 70% of DDLs (7/11) were located in the retroperitoneum. When CD34 expression was evaluated among the groups, a significant difference was observed (p=0.001). CD34 was positive in 92.9% of SCL cases. p16 immunoreactivity was significantly different between the groups (p=0.001). p16 expression was observed in 50.5% of ALT / WDL cases and 79% of DDL cases. p16 and CD34 expression are valuable in the differential diagnosis of lipomatous tumors when radiological and clinical considerations do not help to differential diagnosis of adipocytic tumors. Level IV, Therapeutic Study.

Quantitative signal intensity ratios to distinguish between subfascial lipoma and atypical lipomatous tumor/well-differentiated liposarcoma using short-tau inversion recovery (STIR) MRI

PurposeTo establish simple quantitative variables at short-tau inversion recovery (STIR) magnetic resonance imaging (MRI) to identify lipomas with high specificity in patients with indeterminate subfascial lipomatous tumors. Materials and methodsThe MRI examinations of 26 patients (14 men, 12 women; mean age 63±12.5 [SD] years; range: 40–84years) with histopathologically proven subfascial atypical lipomatous tumors/well-differentiated liposarcomas (ALT/WDLs) and those of 68 patients (32 men, 36 women; mean age, 56±13.5 [SD] years; range: 21–83years) with lipomas were retrospectively reviewed. Ratios derived from region of interest based signal intensity (SI) measurements of tumors and adjacent fat on STIR images were calculated and maximum tumor diameters were noted. Diagnostic parameter capabilities were assessed using ROC curve analysis. Interreader agreement was evaluated by calculation of intraclass correlation coefficients (ICC). ResultsUsing a cut-off value of 1.18, STIR-SI ratios allowed discriminating between lipoma and ALT/WDL (AUC=0.88; P<0.001) yielding 93% specificity (95% CI: 77–99%) and 74% sensitivity (95% CI: 61–84%) for the diagnosis of lipoma. Interreader agreement was excellent (ICC=0.93). A significant difference in maximum tumor diameter was found between ALT/WDLs (mean: 18.1±6.0 [SD] cm; range: 5.6–33.1cm) and lipomas (mean: 9.7±5.0 [SD] cm; range: 2.9–29.1cm) (P<0.001). Using a cut-off of 11cm, maximum tumor diameter allowed discriminating between lipoma and ALT/WDLs with 92% specificity (95% CI: 75–99%) and 69% sensitivity (95% CI: 57–80%). The combination of a STIR-SI ratio<1.4 and maximum tumor diameter<11cm yielded 100% specificity (95% CI: 87–100%) and 65% sensitivity (95% CI: 54–77%) for the diagnosis of lipoma. ConclusionThe combination of STIR-SI ratio and maximum diameter allows discriminating between lipoma and ALT/WDL in initially indeterminate lipomatous tumors.

MDM2 RNA In Situ Hybridization for the Diagnosis of Atypical Lipomatous Tumor: A Study Evaluating DNA, RNA, and Protein Expression.

The distinction of atypical lipomatous tumor/well-differentiated liposarcoma (ALT/WDL) from its benign counterpart, lipoma, may represent a challenge. MDM2 DNA amplification is used as the gold standard as MDM2 immunohistochemistry lacks specificity and sensitivity. Herein, we investigate the diagnostic utility of MDM2 RNA in situ hybridization (RNA-ISH) and compare the test with MDM2 immunohistochemistry and MDM2 DNA fluorescence in situ hybridization (FISH) in benign and malignant lipomatous neoplasms. We evaluated 109 neoplasms including 27 lipomas, 25 spindle cell lipomas, 32 ALTs/WDLs, and 25 dedifferentiated liposarcomas (DDL). The validation cohort included 14 lipoma-like neoplasms that lacked unequivocal features of ALT/WDL and in which MDM2 immunohistochemistry was either equivocal, negative or falsely positive. Immunohistochemistry, automated RNA-ISH and DNA-FISH for MDM2 were performed. Tumors with diffuse nuclear staining or >50 dots per cell on RNA-ISH were considered positive. All lipomas and lipoma variants were negative for RNA-ISH while all ALTs/WDLs and DDLs were positive. Eighty percent (24/30) and 92% (22/24) of ALTs/WDLs and DDLs were positive for MDM2 immunohistochemistry. Lipomas and its variants were negative for MDM2 amplification; 92% and 100% of ALTs/WDLs and DDLs showed MDM2 DNA amplification. The mean percentage of ALT/WDL tumor cells showing MDM2 RNA-ISH positivity was 73% compared with 24% on MDM2 immunohistochemistry. RNA-ISH correctly classified all 10 ALTs/WDLs and all 4 lipomas in the validation cohort. The performance of MDM2 RNA-ISH and MDM2 DNA-FISH are equivalent. MDM2 RNA-ISH can be of diagnostic value in histologically challenging lipomatous neoplasms. The automated MDM2 RNA-ISH assay should allow for more widespread use of MDM2 testing and for a more sensitive and specific diagnosis of ALT/WDL.

Identification of Coiled-Coil Domain–Containing Protein 180 and Leucine-Rich Repeat–Containing Protein 4 as Potential Immunohistochemical Markers for Liposarcoma Based on Proteomic Analysis Using Formalin-Fixed, Paraffin-Embedded Tissue

Recent technical improvements in both mass spectrometry and protein extraction have made it possible to use formalin-fixed, paraffin-embedded (FFPE) tissues for proteome analysis. In this study, comparable proteome analysis of FFPE tissues revealed multiple candidate marker molecules for differentiating atypical lipomatous tumor/well-differentiated liposarcoma (ALT/WDL) from lipoma. A total of 181 unique proteins were identified for ALT/WDL. Of the identified proteins, coiled-coil domain-containing protein 180 (CCDC180) and leucine-rich repeat-containing protein 4 (LRRC4) were studied as candidate markers of ALT/WDL. CCDC180 and LRRC4 immunohistochemistry clearly stained tumor cells of ALT/WDL and dedifferentiated liposarcoma and could differentiate them from lipoma with high accuracy. Cell biological methods were used to further examine the expression of the candidate marker molecules in liposarcoma cells. In liposarcoma cells, knockdown of CCDC180 and LRRC4 inhibited cell proliferation. CCDC180 inhibited cell migration, invasion, and apoptosis resistance in WDL cells. Adipogenic differentiation suppressed the expression of CCDC180 and LRRC4 in WDL cells. These results indicated that LRRC4 and CCDC180 are novel immunohistochemical markers for differentiating ALT/WDLs. Their expression was associated with adipocyte differentiation and contributed to malignant potentials of WDL cells. Proteome analysis using a standard stock of FFPE tissues can reveal novel biomarkers for various diseases, which contributes to the progress of molecular pathology.

Primary endobronchial liposarcoma successfully resected via bronchoscopy: A rare case report with genetic analysis.

Liposarcoma is the most common type of soft-tissue sarcoma, and predominantly originates from the extremities and retroperitoneal cavity. However, primary endobronchial liposarcoma is extremely rare. The present study reports on the case of a 54-year-old man, a smoker, diagnosed with primary endobronchial atypical lipomatous tumor/well-differentiated liposarcoma (ALT-WDLS), which was successfully resected via bronchoscopy. Chest computed tomography (CT) revealed a neoplasm in the left main bronchus measuring 12.8×7.8 mm. Bronchoscopy demonstrated multiple roundish, pedunculated, polypoid masses in the left main bronchus. Bioptic specimens were obtained from the roundish masses, and pathological examination revealed an adipose tissue-derived tumor. The masses were completely resected during the second bronchoscopy under general anesthesia. Histopathological examination of the radical resection specimen revealed that it was an ALT-WDLS. The patient showed good quality of life at the 6-month postoperative follow-up without evidence of recurrence. Immunohistochemistry was completed with the human homologue of murine double-minute type 2 (MDM2) (+), cyclin-dependent kinase 4 (CDK4) (+), p16 (+), S-100 (+), Ki-67 (+), cluster of differentiation 34 (CD34) (+) and retinoblastoma protein (+), confirming ALT-WDLS. However, the fluorescence in situ hybridization assay revealed no amplification of MDM2 and CDK4 in the ALT-WDLS. To the best of our knowledge, the present case report is the first to describe the clinicopathologic features and genetic analysis of endobronchial liposarcoma. Although rare, this case is a reminder that clinicians should consider the possibility of this rare endobronchial tumor in patients with nonspecific symptoms including chronic cough, chest pain and recurrent pneumonia. As in this case, endoscopic treatment provided an excellent clinical outcome in patients with primary endobronchial ALT-WDLS.

Primary Breast Atypical Lipomatous Tumor/ Well-Differentiated Liposarcoma and Dedifferentiated Liposarcoma.

Atypical lipomatous tumor/well-differentiated liposarcoma (ALT/WDL) and its higher-grade counterpart, dedifferentiated liposarcoma (DDL), are extraordinarily rare tumors in the breast. The main differential diagnostic consideration of primary breast ALT/WDL is malignant phyllodes tumor with liposarcomatous differentiation, and the main differential diagnostic consideration of DDL in the breast is metaplastic breast carcinoma, particularly the spindle cell type, with heterologous sarcomatous differentiation. These differential diagnoses may be particularly challenging when evaluating limited core needle biopsy sampling. MDM2 and/or CDK4 protein overexpression and gene amplification are beneficial ancillary studies that can help establish the diagnosis of primary breast ALT/WDL and DDL, and effectively rule out the diagnoses of malignant phyllodes tumor and metaplastic breast carcinoma.

Adipocyte size variability in benign and malignant lipomatous tumors and morphologic mimics: a quantitative definition using digital pathology

Among well-differentiated lipomatous lesions, variability in adipocyte size has been proposed as a morphologic feature of malignancy. Specifically, normal adipose tissue and benign lipomas tend to contain adipocytes of uniform size, whereas atypical lipomatous tumor/well-differentiated liposarcoma (ALT/WDL) is described as containing adipocytes with a conspicuous variation in cell size. However, this proposed variance has never been objectively, quantitatively correlated with diagnosis. Using whole-slide scanning combined with semiautomated digital image analysis, we aimed to quantitatively test the hypothesis that variance in adipocyte size is a feature of malignancy in well-differentiated lipomatous tumors. Whole-slide scanning was performed on representative hematoxylin and eosin-stained slides selected from 130 cases representing benign (lipoma, spindle cell lipoma) and malignant lipomatous neoplasms (ALT/WDL) and morphologic mimics (normal adipose tissue, fat necrosis, fat atrophy). A previously validated, open source software package (Fiji-based Adiposoft) was used in semiautomated analysis of adipocyte size from a representative 1-cm2 portion of each slide. Median, range, and variance of cell sizes were compared across all diagnoses. Fat atrophy demonstrated smaller adipocyte cell size compared with other diagnoses. Among the remaining diagnostic groups, no significant differences were identified in adipocyte size or variance by objective quantitative morphologic analysis. However, the maximum range of adipocyte size was significantly higher in ALT/WDL than conventional lipoma and spindle cell lipoma. These data quantitate the morphology of ALT/WDL and its mimics and more specifically define the somewhat subjective "variability" of cell size as maximum range, rather than variance, of adipocyte size.

Do Mesenchymal Stem Cells Derived From Atypical Lipomatous Tumors Have Greater Differentiation Potency Than Cells From Normal Adipose Tissues?

The p53 protein in mesenchymal stem cells (MSCs) regulates differentiation to osteogenic or adipogenic lineage. Because p53 function is depressed in most malignancies, if MSCs in malignancy also have p53 hypofunction, differentiation therapy to osteogenic or adipogenic lineage may be an effective treatment. We therefore wished to begin to explore this idea by evaluating atypical lipomatous tumor/well-differentiated liposarcoma (ALT/WDL) cells, because murine double minute 2 (MDM2) gene amplification, which leads to p53 hypofunction, is found in almost all ALT/WDLs. We compared osteogenic and adipogenic differentiation potency between MSCs isolated and cultured from normal adipose tissues and ALT/WDLs from the same patients. During tumor resections in six patients with ALT/WDL, we analyzed 3 mL of tumor, and for comparison, we harvested a similar amount of normal-appearing subcutaneous adipose tissue from an area remote from the tumor for comparison. Adipogenic differentiation potency was quantitatively assessed using spectrometry after oil red O staining. Osteogenic differentiation potency was semiquantitatively assessed by measuring a specific colored area after alkaline phosphatase (ALP) and alizarin red S staining. ALP is related to preosseous cellular metabolism, and alizarin red is related to calcium deposits in cell culture. There were three observers for each assessment, and each assessment (including induced-differentiation and histologic analysis) was performed in duplicate. We then analyzed the mechanism of the difference of osteogenic differentiation potency using the MDM2-specific inhibitor Nutlin-3 at various concentrations. In terms of adipogenic differentiation potency, contrary to our expectations, more fatty acid droplets were observed in MSCs derived from normal fat than in MSCs derived from ALT/WDL, although we found no significant difference between MSCs derived from ALT/WDL and MSCs derived from normal fat; the mean differentiation potency values (normal adipose tissue versus ALT/WDL) (± SD) were 0.34 (SD, ± 0.13; 95% CI, 0.24-0.44) versus 0.25 (SD, ± 0.10; 95% CI, 0.18-0.33; p = 0.22). By contrast, we found greater osteogenic differentiation potency in MSCs derived from ALT/WDL than in MSCs derived from normal fat. The mean differentiation potency values (normal adipose tissue versus ALT/WDL) (±SD) based on ALP staining was 1.0 versus 17 (SD, ± 36; 95% CI, -2.8 to 38; p = 0.04). However, we found no differences based on alizarin red S staining; mean differentiation potency value (normal adipose tissue versus ALT/WDL) (± SD) was 1.0 versus 4.2 (SD, ± 4.8; 95% CI, 1.3-7.2; p = 0.58). The gap of osteogenic differentiation potency between MSCs from normal adipose tissue and ALT/WDL was decreased as MDM2-inhibitor Nutlin-3 concentration increased. MSCs derived from ALT/WDL had higher osteogenic differentiation potency based on ALP staining, which disappeared as Nutlin-3 concentration increased, suggesting that could be caused by amplified MDM2 in ALT/WDL. Future laboratory studies might mechanistically confirm the gene and protein expression, and based on the mechanism of the gap of differentiation potency, if p53 contrast between MSCs in tumor and normal tissue could be stimulated, less-toxic and more-effective differentiation therapy to MSCs in malignancies might be developed.

MDM2 and CDK4 Immunohistochemistry: Should It Be Used in Problematic Differentiated Lipomatous Tumors?: A New Perspective.

Although most cases of atypical lipomatous tumor/well-differentiated liposarcoma (ALT/WDL) can be diagnosed solely on the basis of histologic features, those lacking diagnostic histologic features require ancillary studies for accurate classification. Fluorescent in situ hybridization (FISH) for amplification of MDM2 has been considered the gold standard for diagnosis in these situations. Immunostaining for MDM2 and/or CDK4 has been adopted as a surrogate method because of its high concordance rate with FISH and lower cost. However, studies examining the concordance of the 2 methods have been based preferentially on cases in which the diagnosis could be established histologically. No study has explored the concordance between the 2 methods in histologically ambiguous cases or in cases in which the diagnosis of ALT/WDL is not apparent after a review of all slides. To address this, we performed immunostaining for MDM2 and CDK4 on 183 well-differentiated lipomatous tumors that could not be diagnosed on purely histologic grounds and that were, therefore, subjected to FISH analysis. These included ALT/WDLs (n=56), lipomas (n=96), and lipoma variants (n=31). Staining for MDM2 and CDK4 was noted in 25/56 and 23/56 ALT/WDL, respectively, giving a sensitivity of 45% and 41% and a specificity of 98% and 92%. Staining was noted exclusively in the nuclei of atypical cells and not in the nuclei of adipocytes. Staining for MDM2 and CDK4 occurred in 2/125 and 10/117 benign lipomatous lesions, respectively. False-positive staining was equivalent in intensity to ALT/WDL. We conclude that MDM2 and CDK4 staining is a relatively insensitive method for diagnosing ALT/WDL in cases that are histologically ambiguous, as staining is restricted to neoplastic cells with atypia that are underrepresented in these cases. Therefore, in cases like ours that closely simulate clinical practice, FISH is the more reliable and cost-effective option.

Differential diagnosis of atypical lipomatous tumor/well-differentiated liposarcoma and dedifferentiated liposarcoma: utility of p16 in combination with MDM2 and CDK4 immunohistochemistry

The differential diagnosis between atypical lipomatous tumor/well-differentiated liposarcoma (ALT/WDLPS) and dedifferentiated liposarcoma (DDLPS) from their morphologic counterparts is challenging. Currently, the diagnosis is guided by MDM2 and CDK4 immunohistochemistry (IHC) and is confirmed by the amplification of the corresponding genes. Recently, p16 IHC has been proposed as a useful diagnostic biomarker. The objective was to assess the utility of p16 IHC in the differential diagnosis of ALT/WDLPS and DDLPS. Our series included 101 tumors that were previously analyzed using fluorescence in situ hybridization for MDM2 and CDK4 amplification. We compared sensitivity and specificity of p16 IHC to MDM2 and CDK4 IHC in the differential diagnosis of ALT-WDLPS (n=19) versus benign adipocytic tumors (n=44) and DDLPS (n=18) versus mimicking sarcomas (n=20). In the differential diagnosis of ALT-WDLPS, p16 had a sensitivity of 89.5% but a specificity of 68.2%, which was impaired by false-positive lipomas with secondary changes, especially in biopsies. Likewise, in the differential diagnosis of DDLPS, p16 had a sensitivity of 94.4% and a specificity of 70%, which hampered its use as a single marker. However, adding p16 to MDM2 and/or CDK4 increased diagnostic specificity. Indeed, MDM2+/p16+ tumors were all ALT-WDLPS, and MDM2-/p16- tumors were all benign adipocytic tumors. Moreover, all MDM2+/CDK4+/p16+ tumors were DDLPS, and the MDM2-/CDK4-/p16- tumor was an undifferentiated sarcoma. Although the use of p16 as a single immunohistochemical marker is limited by its specificity, its combination with MDM2 and CDK4 IHC may help discriminate ALT-WDLPS/DDLPS.

MDM2 Amplification in Problematic Lipomatous Tumors: Analysis of FISH Testing Criteria.

To discriminate lipomas from atypical lipomatous tumor/well-differentiated liposarcoma (ALT/WDL) we perform fluorescence in situ hybridization (FISH) for MDM2 amplification in several problematic situations: "lipomas" >10 cm, lesions with equivocal atypia, recurrent "lipomas," all retroperitoneal/pelvic/abdominal "lipomas", and in cases not fitting the above criteria but having worrisome clinical or radiologic features. To ascertain the validity of these criteria, we have reviewed our experience with 301 consecutive differentiated lipomatous tumors in which the diagnosis of ALT could not be established on the basis of histologic sections and in which FISH was performed on the basis of the above criteria. The final diagnosis was based on MDM2 amplification status. Given the nature of this study to evaluate difficult lesions, most cases included (74%) were received in consultation. This enhanced our study series for borderline cases, and the data presented may not be generalizable to adipocytic tumors seen outside a subspecialty setting. Of 301 cases, 108 proved to be ALT/WDL (36%). The most common test indication was size >10 cm (n=187), followed by equivocal atypia (n=145), retroperitoneal/pelvic/abdominal location (n=86), recurrence (n=33), and clinical concern (n=12). Of the tumors >10 cm, 68 (36%) proved to be ALT/WDL, whereas the remainder were interpreted as lipoma or its variants (eg, spindle cell or pleomorphic lipoma). The 2 groups did not differ statistically in size, although ALTs consistently occurred in patients above 50 years of age. Of the cases with equivocal atypia, 72 (50%) proved to be ALT/WDL. Those in the retroperitoneum/abdomen/pelvis were ALT/WDL in 30 cases (35%), and those that had recurred were ALT in 18 cases (55%). Recurrence, atypia, and having multiple indications for testing were more common in ALT than in benign lesions (P=0.02, 0.0001, 0.0012, respectively). No ALT/WDL occurred in the hands and feet, and only a single ALT/WDL was superficial (1 ALT/WDL vs. 60 lipoma/spindle cell or pleomorphic lipoma). Small (<10 cm) retroperitoneal tumors without additional features were always benign (n=9). On the basis of our results, FISH testing is recommended for: (1) recurrent lesions; (2) deep extremity lesions that are >10 cm in patients over 50 years of age; (3) in cases with equivocal atypia; (4) in lesions of the retroperitoneum/pelvis/abdomen, and in special clinical situations as directed by treating clinicians. Testing is low yield in superficial lesions, in small extremity lesions without additional indicators for testing, in large extremity lesions without additional features in patients under the age of 50, and in lesions arising in the hands/feet. More evidence is needed regarding testing in small retroperitoneal lesions without additional features. By adopting these criteria, we could have avoided testing 74 cases, missing a single superficial ALT/WDL.