Well-differentiated Retroperitoneal Liposarcoma Research Articles

Imaging features of perinephric myxoid pseudotumors of fat.

Retrospectively evaluate multimodality imaging features of perinephric myxoid pseudotumor of fat (PMPTF). Institutional cases of PMPTF with CT, MRI and/or ultrasound evaluation from 1/1/2020 to 9/1/2023 were retrospectively reviewed. Patient demographics and clinical history were reviewed, and imaging features recorded. 14 patients with pathologically-proven PMPTF were identified (11M, 3 F; mean age 66.7 ± 17.0years; range 40-87years). Three patients (18%) had bilateral lesions; a total of 17 PMPTFs were reviewed. 15/17 (88%) were biopsy-proven; two cases were diagnosed by imaging only in patients with a contralateral biopsy-proven PMPTF. All evaluable specimens were negative for MDM2 amplification. 11/17 (65%) occurred in patients with renal disease, including 4/17 (24%) in patients with renal transplant. 100% (17/17) had CT, 11/17 (65%) MRI, and 6/17 (35%) ultrasound. The mean largest lesion dimension was 10.9 ± 4.6cm (range 4.3-17.0cm). Of cases involving native kidneys, 7/13 (54%) presented as multifocal perinephric masses and 5/13 (38%) as a solitary perinephric mass. All four transplant cases presented as infiltrative-appearing masses involving the renal sinus with lesser perinephric involvement. 14/17 (82%) lesions contained macroscopic fat on CT and MRI and 3/17 (18%) showed no macroscopic fat, all involving renal transplants. All cases with MRI demonstrated T2 hyperintensity with signal dropout on opposed-phase imaging. 11/13 (85%) PMPTF showed no or equivocal CT enhancement. Enhancement was better seen on MRI in all cases evaluated by both CT and MRI. Of the six PMPTFs imaged by ultrasound, four (67%) were heterogeneously hypoechoic and two (33%) had mixed regions of hypo-, iso- and hyperechogenicity relative to adjacent renal parenchyma. PMPTF is a rare, benign, and underrecognized lesion that may mimic malignancy, particularly retroperitoneal well-differentiated liposarcoma. The imaging features of this unusual pseudosarcoma differ in native and transplanted kidneys. Improved awareness of this entity will facilitate appropriate patient management and avoid unnecessary intervention.

Multi-omics joint analysis revealed the metabolic profile of retroperitoneal liposarcoma.

Retroperitoneal liposarcoma (RLPS) is the main subtype of retroperitoneal soft sarcoma (RSTS) and has a poor prognosis and few treatment options, except for surgery. The proteomic and metabolic profiles of RLPS have remained unclear. The aim of our study was to reveal the metabolic profile of RLPS. Here, we performed proteomic analysis (n = 10), metabolomic analysis (n = 51), and lipidomic analysis (n = 50) of retroperitoneal dedifferentiated liposarcoma (RDDLPS) and retroperitoneal well-differentiated liposarcoma (RWDLPS) tissue and paired adjacent adipose tissue obtained during surgery. Data analysis mainly revealed that glycolysis, purine metabolism, pyrimidine metabolism and phospholipid formation were upregulated in both RDDLPS and RWDLPS tissue compared with the adjacent adipose tissue, whereas the tricarboxylic acid (TCA) cycle, lipid absorption and synthesis, fatty acid degradation and biosynthesis, as well as glycine, serine, and threonine metabolism were downregulated. Of particular importance, the glycolytic inhibitor 2-deoxy-D-glucose and pentose phosphate pathway (PPP) inhibitor RRX-001 significantly promoted the antitumor effects of the MDM2 inhibitor RG7112 and CDK4 inhibitor abemaciclib. Our study not only describes the metabolic profiles of RDDLPS and RWDLPS, but also offers potential therapeutic targets and strategies for RLPS.

Overexpression of ASPH protein predicts poor outcomes in retroperitoneal liposarcoma patients.

Overexpression of ASPH protein predicts poor outcomes in retroperitoneal liposarcoma patients.

Rapid and Progressive Transformation of Well-Differentiated Retroperitoneal Liposarcoma to Poorly Differentiated Type: A Case Report

Rapid and Progressive Transformation of Well-Differentiated Retroperitoneal Liposarcoma to Poorly Differentiated Type: A Case Report

Challenging surgical treatment of giant retroperitoneal liposarcoma: A case report

Liposarcoma is a rare malignant tumor type and surgical resection is the gold standard treatment. The present study reported on the case of a 51-year-old woman who presented with a mass in the left upper abdomen. Computed tomography revealed a 32-cm giant retroperitoneal liposarcoma. Complete tumor resection was performed without the removal of other organs. Postoperative pathological examination indicated retroperitoneal well-differentiated liposarcoma and immunohistochemistry revealed S-100(−), MDM2(+), vimentin(+), CDK4(+), p16(+) and STAT6(+) results. The patient recovered well after the surgery. Complete tumor resection during the first surgery is key to cure liposarcoma. The present case report will be helpful for clinical oncologists to fully understand giant retroperitoneal liposarcoma and treat it accordingly.

A transcriptomic analysis of retroperitoneal well differentiated liposarcoma (WDLPS) and well differentiated (WD) and dedifferentiated (DD) components of dedifferentiated liposarcoma (DDLPS).

e23520 Background: Retroperitoneal DDLPS is an aggressive tumor characterized by a WD component, morphologically similar to a WDLPS, and a DD component that drives patient prognosis. We aimed at unraveling whether WDLPS and DDLPS are distinct entities or entail a progressive evolution from WDLPS to DDLPS through a transcriptomic analysis. Methods: A transcriptomic analysis was performed in a retrospective series of 107 patients with primary retroperitoneal WDLPS (N = 68, 63.5%) or DDLPS (N = 39, 36.5%) who underwent surgery (2011-15). Paired DD, WD, and normal fat (NF) components were sampled in DDLPS, while paired WD and NF components were sampled in WDLPS. RNA-Seq data were normalized according to the trimmed mean of M-value (TMM) algorithm and differential expression was evaluated with the voom method implemented into the edgeR package. Enrichment in hallmark gene sets from Molecular Signatures Database (MSigDB) was evaluated with gene sets enrichment analysis (GSEA), by using t-statistic as measure of ranking. A false discovery rate (FDR) adjusted p-value < 0.05 was considered for statistical significance. Results: Differential expression analysis revealed marked transcriptional changes within paired components of DDLPS (DD, WD, NF) and WDLPS (WD, NF). Changes of WD and NF components between WDLPS and DDLPS were not statistically significant. Gene sets were analyzed to evaluate the ensemble and overcome the FDR correction applied to single genes. Hallmarks deregulated in WD component of DDLPS compared to WDLPS were detected also in their paired DD component. Among them, G2M checkpoint and mitotic spindle were up-regulated, while adipogenesis, fatty acid metabolism, cholesterol homeostasis, oxidative phosphorylation, and peroxisome were down-regulated. These differences persisted also when NF components were compared with their paired WD component of DDLPS and WDLPS. G2M checkpoint and mitotic spindle gene sets did not differ between NF of DDLPS and NF of WDLPS, suggesting these two hallmarks as tumor-specific. Conversely, expression of adipogenesis, fatty acid metabolism, and oxidative phosphorylation was up-regulated together with other gene sets related to metabolism in NF of DDLPS. Tumor inflammation and interferon response were up-regulated in WD components compared to their paired NF components. Also, interferon response was down-regulated in WD component of DDLPS compared to WDLPS, and inflammation was down-regulated in DD component compared to both WD components. Conclusions: Transcriptomic changes that distinguished WDLPS and WD component of DDLPS increased progressively also in the paired DD component of DDLPS, supporting the hypothesis of a progression from WDLPS to DDLPS in some liposarcomas. Changes observed in NF may suggest a paracrine effect sustaining tumor dedifferentiation.

Giant retroperitoneal well-differentiated liposarcoma presenting in emergency with intestinal occlusion: Case report and review of the literature.

Introduction and importanceLiposarcoma (LPS) represents the most common type of retroperitoneal sarcoma (RPS) and can be classified into four subtypes. Preoperative diagnosis of retroperitoneal liposarcoma (RLPS) is a challenge because of its late and nonspecific clinical presentation. Imaging may be helpful for determining the correct diagnosis. Surgery represents a potentially curative treatment of RLPS.Case presentationA 55-year-old Caucasian female presented to the Emergency Department with a two-day history of abdominal pain, abdominal distension, inability to pass gas or stool, nausea, vomiting and lipothymia. Abdominal examination revealed abdominal distention, abdominal pain without obvious muscle guarding and a giant non-tender mass. Laboratory tests reported neutrophilic leukocytosis and anemia. Abdominal contrast-enhanced computed tomography (CECT) showed a heterogeneous and hypodense giant retroperitoneal mass compressing and displacing the surrounding organs and vessels. The patient underwent excision of a giant retroperitoneal mass. The postoperative course of the patient was uneventful.Clinical discussionRLPS is a malignant neoplasm that can slowly grow to enormous size with possible involvement of adjacent organs and vessels; it may recur locally and has a minimal capacity to metastasize. Preoperative diagnosis and staging of RLPS are important to establish appropriate management and prognosis. Surgery represents the gold standard for non-metastatic RLPS treatment.ConclusionRLPS is a rare malignant neoplasm generally difficult to detect early due to its late and nonspecific clinical presentation. CECT represents the most commonly used modality for diagnosis, staging and preoperative evaluation. Surgery represents the appropriate treatment of non-metastatic RLPS.

Real-world use of palbociclib monotherapy in retroperitoneal liposarcomas at a large volume sarcoma center.

Palbociclib has been evaluated in early phase trials for well-differentiated liposarcoma (WDLPS) and dedifferentiated liposarcoma (DDLPS) patients, with reported median progression-free survival (PFS) of 18 weeks. Here, we report on real-world use and surgical outcomes associated with palbociclib treatment. We retrospectively reviewed 61 consecutive patients with retroperitoneal WDLPS (n=14) or DDLPS (n=47) treated with palbociclib monotherapy between 1 March 2016 and 28 February 2021 at The University of Texas MD Anderson Cancer Center. At palbociclib initiation, median age was 64 (interquartile range [IQR] 56-72). In WDLPS and DDLPS cohorts, the median number of prior systemic treatments was 0 (IQR 0-0) and 2 (IQR 0-4), respectively. Median number of prior surgeries was 2 (WDLPS IQR 1-2.75) and 2 (DDLPS IQR 1-3). Median PFS was 9.2 (WDLPS IQR 3.9-21.9) and 2.6months (DDLPS IQR 2.0-6.1), with median time on treatment of 7.4months (WDLPS IQR 3.5-14.2) and 2.7months (DDLPS IQR 2.0-5.7). Twelve patients ultimately underwent surgical resection. Resections were macroscopically complete (R0/R1) in half (n=6/12), among whom only one patient experienced relapse after resection (median follow-up 7.5months). All patients who underwent macroscopically incomplete resections progressed after surgery with median time to progression of 3.3months (IQR 2.3-4.4). Surgery after palbociclib treatment was not associated with improved overall survival. Efficacy of palbociclib monotherapy for patients with advanced WDLPS and DDLPS is disappointing. While palbociclib may have been used to delay surgery, there was no clear benefit from treatment and few patients achieved prolonged tumor control.

Sepsis versus anaphylaxis—differentiating shock etiology: a case report involving Smoflipid

: This case study illustrates a clinically observed interaction between Smoflipid and the development of anaphylactic shock in a patient on long-term parenteral nutrition. This patient had a history of a well-differentiated retroperitoneal liposarcoma, now resected, which was complicated by duodenal perforation and intraperitoneal drain placement; due to significant gastrointestinal tract dysfunction the patient was maintained on continuous parenteral nutrition via a peripherally inserted central catheter (PICC) line. Following a routine and drain exchange, the patient was admitted to the hospital. The patient subsequently developed anaphylactic-like shock symptomatology, necessitating admission to the critical care unit. Intermittent dual vasopressor use was required. There was also an intermittently visible rash that was noted. The etiology of the shock state was unclear. After review of the patient’s case and clinical course, a potential etiology of his shock state was the inpatient protocolized substitution of Smoflipid instead of Intralipid in the parenteral nutrition regimen. After consultation with Allergic Diseases, Nutrition, and Pharmacy the Smoflipid was discontinued and the patient’s regimen was reverted to the standing home regimen including Intralipid. Following discontinuation of Smoflipid and resumption of Intralipid, the shock physiology resolved. The patient was subsequently transferred from the critical care unit and discharged soon thereafter by the primary surgical service. A formal Allergic Disease evaluation was completed in the outpatient setting. Continuous parenteral nutrition therapy was maintained at home using the previous home Intralipid regimen without issue. This case illustrates a multidisciplinary approach including Surgery, Allergic Diseases, Nutrition, Pharmacy, and Critical Care to address the patient’s acute shock state. In addition, a review of different shock states is presented. A literature review evaluating side effects of Smoflipid and an association of shock to its use is presented.

Low and moderate grade retroperitoneal liposarcoma: Is adjuvant radiotherapy associated with improved survival in patients undergoing R1 resection?

BackgroundFew studies evaluate the efficacy of adjuvant radiotherapy (aXRT) in patients with retroperitoneal liposarcoma undergoing resection to histologically positive (R1) margins. MethodsWe queried the National Cancer Database to identify patients undergoing R1 resection for localized, large (>5 cm) low and moderate grade retroperitoneal liposarcoma between 2004 and 2016. Kaplan Meier method was used to compare overall survival (OS) for patients receiving aXRT to a 1:2 propensity-matched cohort of patients undergoing resection alone. ResultsA total of 322 (76.5%) patients underwent R1 resection alone, while 99 (23.5%) underwent resection followed by aXRT. The 99 receiving aXRT were successfully 1:2 propensity-score matched to 198 undergoing resection alone. There was no difference in 5-year OS between matched cohorts (69.7% vs 76.2%, p = 0.40). ConclusionsIn patients undergoing R1 resection of moderate- and well-differentiated retroperitoneal liposarcoma, use of aXRT is not associated with an improvement in OS.

THE PROGNOSTIC SIGNIFICANCE OF MYXOID MATRIX IN RETROPERITONEAL WELL-DIFFERENTIATED LIPOSARCOMA

Objective: to assess the influence of the myxoid matrix in retroperitoneal well-differentiated liposarcoma(WDLPS ) on the long-term results of surgical treatment of patients.Material and Methods. The study included 111 patients with primary retroperitoneal WDLPS who underwent radical surgical treatment in Federal State Budgetary Institution «N.N. Blokhin National Medical Research Center of Oncology» of the Ministry of Health of the Russian Federation. Histological slides of all surgical specimens were reviewed by experienced pathologist and reclassified according to criteria of WHO (2013) for histological subtypes of the WDLPS . Patients were divided into groups depending on presence or absence of the myxoid matrix in WDLPS and enrolled in intergroup analysis of overall (OS ) and recurrence-free (RFS) survival.Results. OS was significantly worse in the group of patients with the myxoid matrix in the tumor (p=0.002; log-rank test). The median OS was 142 (95 % CI , 108, 176) months in the group without the myxoid matrix, and 84 (95 % CI , 29, 139) months in the group with the myxoid matrix. The 5-year survival rates were 79 % and 44 % in the groups without myxoid matrix and with myxoid matrix, respectively. RFS was also significantly worse in the group of patients with the myxoid matrix than in the group of patients without the myxoid matrix (p=0.006; log-rank test). The median RFS was 55 (95 % CI , 38, 72) months in the WDLPS group without the myxoid matrix, and 31 (95 % CI , 15, 47) months in the WDLPS group with the myxoid matrix. The 2-year RFS rates were 75 % and 44 % in the groups without the myxoid matrix and with the myxoid matrix, respectively.Conclusion. The results of the study demonstrated that the presence of the myxoid matrix in WDLPS was associated with poor prognosis. We believe that the presence of the myxoid matrix in WDLPS can serve as an effective morphological marker of a less favorable prognosis for retroperitoneal WLPS .

Synchronous Renal Dedifferentiated Liposarcoma and Retroperitoneal Well-Differentiated Liposarcoma: A Case Report With Literature Review.

Liposarcoma is the most common soft tissue malignancy and usually occurs in the retroperitoneum or the extremities but rarely in the kidney. In this article, we report a case of a 71-year-old female patient who presented with abdominal lump and left flank pain for 1 month. An abdominal contrast-enhanced computed tomography scan demonstrated a 12 cm × 7 cm solid mass arising from the upper pole of left kidney and another 8 cm × 6 cm low-density retroperitoneal mass with fat density. Radical nephrectomy of the left kidney and resection of the retroperitoneal mass were performed. Surprisingly, pathological examination revealed a high-grade sarcoma (with minor lipomatous component) in the left kidney and a retroperitoneal well-differentiated liposarcoma. MDM2 gene amplification was identified by fluorescence in situ hybridization in both tumors, supporting final diagnosis of dedifferentiated liposarcoma of the kidney and well-differentiated liposarcoma of the retroperitoneum.

Invasive potential of retroperitoneal well-differentiated liposarcomas depending on the extent of sclerosing component in the tumor

Objective. To assess the influence of the extent of sclerosing component in the retroperitoneal well-differentiated liposarcoma (WDLPS) on the survival.
 Material and methods. The retrospective study included 111 patients with primary retroperitoneal WLPS who underwent radical surgical treatment in Federal State Budgetary Institution N.N. Blokhin National Medical Research Center of Oncology. Histological slides of all surgical specimens were reviewed by experienced pathologist and reclassified according to criteria of WHO (2013). Patients were divided into groups depending on the extent of the sclerosing component in the tumor and enrolled in intergroup analysis. We analyzed relationship between extent of the sclerosing component in the tumor and frequency of the pathologically confirmed visceral invasion. Also, we have analyzed the influence of the visceral invasion of WDLPS on the long-term results overall (OS) and recurrence-free (RFS) survival.
 Results. Pathologically confirmed visceral invasion was revealed in 17% of cases with the sclerosing component less 20%, and in 31% of cases with the sclerosing component more 20%. OS was significantly worse in the group of patients who suffered from WDLPS with visceral invasion than in the group of patients without visceral invasion (p = 0.009; logarithmic criterion). The median OS in the compared groups was 85 (95% CI, 84, 87) and 142 (95% CI, 109, 175) months, the 5-year OS rate was 41% and 86%, respectively. RFS was significantly worse in the group of patients with histologically confirmed visceral invasion than in the group without organ invasion (p = 0.001; logarithmic criterion). Median RFS in the compared groups was 26 (95% CI, 20, 32) and 57 (95% CI, 38, 76) months, 2-year RFS 33% and 85%, respectively.
 Conclusion. Results of the study demonstrate more aggressive behavior of WDLPS with increasing extent of the sclerosing component. We believe that semi-quantitative counting of sclerosing component in retroperitoneal WDLPS can serve as an effective morphological marker of a less favorable prognosis of the disease.

Evaluating the Impact of Surveillance Follow-Up Intervals in Patients Following Resection of Primary Well-Differentiated Liposarcoma of the Retroperitoneum.

Resection of recurrent retroperitoneal well-differentiated liposarcoma (RP-WDLPS) is unlikely to result in cure. Thus, most clinicians delay surgery after recurrence until symptom intolerance or increasing rate of disease progression. The aim of this study was to determine whether longer surveillance intervals in this population would impact outcomes or delay treatment in those who recur. A retrospective review of patients with primary RP-WDLPS who underwent resection between April 1996 and April 2017 and surveillance at MDACC (n = 91) was performed. Median age at diagnosis of primary RP-WDLPS was 61years; median tumor size was 30cm. Complete resection was achieved in 85 (93.4%) patients. Among patients who underwent complete resection, recurrence occurred in 53 (60.2%) with median time to recurrence of 27.0months. Thirty-six (69.6%) of these patients underwent resection of recurrent disease at a median 40.2months from primary tumor resection. Surveillance imaging at 4-month (vs 3-month) intervals would not have impacted recurrence management in 84 (95.5%) patients; imaging at 6-month (vs 3-month) intervals would not have impacted management of recurrence in 80 (90.9%). Recurrence was common, often occurring beyond the early postoperative period following primary RP-WDLPS resection. More frequent surveillance imaging (q3-4 vs q6 months) in the first 2years following primary RP-WDLPS resection may not significantly impact timing of surgery or systemic therapy for recurrence. If longer surveillance intervals were shown to be safe with equivalent outcomes in prospective studies, the resulting change in practice could lead to decreased anxiety and cost for patients and healthcare systems.

ASO Author Reflections: Surveillance After Resection of Retroperitoneal Well-Differentiated Liposarcoma: A Balancing Act Between Earlier Recurrence Detection, Patient Anxiety, and Health Care Resource Expenditure.

ASO Author Reflections: Surveillance After Resection of Retroperitoneal Well-Differentiated Liposarcoma: A Balancing Act Between Earlier Recurrence Detection, Patient Anxiety, and Health Care Resource Expenditure.

Paraneoplastic myasthenia gravis in a 62 year old Filipino woman with a well-differentiated retroperitoneal liposarcoma: A case report

V.G., is a 62 year old woman, housewife, known hypertensive and asthmatic, from Cebu City admitted due to ptosis and an enlarging abdominal mass. Two years PTA, patient had onset of bilateral ptosis associated with occasional diplopia. She just tolerated the condition and no consult was done. Eighteen months PTA, she noted a soft, palpable, non tender, round mass on the right lower abdominal area. There were no associated changes in bowel and bladder pattern or weight loss. Two weeks PTA, abdominal girth increased causing occasional exertional dyspnea. She sought consult with a gastroenterologist. Computed tomography scan of the whole abdomen revealed a large retroperitoneal mass, suggestive of a large Liposarcoma. She underwent an exploratory laparotomy, adhesiolysis, and radical excision of the retroperitoneal mass. Histopathologic gross examination of the specimen revealed that the mass weighed 800 grams, and measured 441 X 331 X 120 cm. Microscopic examination showed a neoplasm consisting of lobules of adipose cells, which were traversed by fibrocollagenous septae of varied thickness consistent with a well differentiated Liposarcoma. Three years after surgey, she noted progression of bilateral ptosis now associated with facial weakness and generalized muscle fatigue that markedly improved with rest. She was admitted at a local hospital where Paraneoplastic Myasthenia Gravis with a Liposarcoma was considered. Cranial and Chest CT scans were unremarkable. Pyridostigmine test was positive with improvement of ptosis, diplopia, and muscle weakness. Anti-acetylcholine receptor radioimmunoassay was positive for AchR antibodies. She was treated with intravenous immunoglobulin (IVIG) and was discharged with Pyridostigmine (Mestinon) as maintenance.

ASO Author Reflections: Recurrent Retroperitoneal Well-Differentiated Liposarcoma.

ASO Author Reflections: Recurrent Retroperitoneal Well-Differentiated Liposarcoma.

Salvage Surgery for Recurrent Retroperitoneal Well-Differentiated Liposarcoma: Early Reoperation may not Provide Benefit.

Current evidence regarding salvage resection for recurrent retroperitoneal (RP) sarcomas generally lacks detailed histology-specific analyses, but the aggressiveness of these tumors varies widely by histology. We investigated associations between timing and extent of salvage surgery and survival outcomes in patients with recurrent RP well-differentiated liposarcoma (WDLPS). The University of Texas MD Anderson Cancer Center Surgical Oncology sarcoma database was reviewed to identify patients with RP WDLPS who underwent surgical resection for first recurrent disease (salvage surgery) in 1995-2015. Medical records were retrospectively reviewed to identify factors associated with overall survival and disease-free survival. We identified 52 patients who underwent salvage surgery for RP WDLPS for first local recurrence; 28 (54%) underwent salvage surgery within 6months after recurrence. Concomitant organ resections were performed in 32 (62%) patients, 4 (13%) of whom had pathologic invasion of resected organs. After R0/R1 resections (n = 45), 38 (84%) experienced a second local recurrence. Multivariable analyses revealed that organ invasion at the primary surgery [hazard ratio (HR) 13.08; p = 0.005] and disease-free interval < 1year (HR 3.64; p = 0.044) were associated with shorter overall survival. Recurrence-to-salvage interval < 6months was associated with shorter disease-free survival (HR 2.18; p = 0.025). Concomitant organ resection was associated with a longer hospital stay: ≥ 14days (odds ratio 21.58; p = 0.007). Early salvage surgery may not always be the best approach for recurrent RP WDLPS patients. Because organ invasion is rare among recurrent RP WDLPS patients and concomitant organ resection is associated with a longer hospital stay, preservation of uninvolved organs should be considered.

Expression of MDM2 and p16 in angiomyolipoma

Angiomyolipoma (AML) arises primarily from the kidney but may grow into the retroperitoneal space mimicking a primary retroperitoneal tumor. Fine needle aspiration (FNA) and core needle biopsy of AML, particularly the fat-predominant variant, may be difficult to distinguish from retroperitoneal well-differentiated liposarcoma (WDLS) or lipoma. Commonly used immunomarkers, MDM2 and p16, have proven useful in diagnosing WDLS and dedifferentiated liposarcoma (DDLS), while HMB45 and Melan-A are melanocyte-related markers characteristically expressed in AML. In this study, we investigated the utility of MDM2 and p16 along with HMB45 and Melan-A immunohistochemical analysis in distinguishing AML from WDL/DDLS or lipoma. Immunohistochemically, AMLs demonstrated focal MDM2 expression (40% of cases) and focal/diffuse expression of p16 (60%). AMLs marked focally or diffusely with HMB45 (76% of cases) and Melan-A (96%). These latter two immunomarkers were not expressed in any of the WDLS/DDLSs or lipomas tested. WDLS/DDLSs showed focal/diffuse expression of MDM2 (91% of cases) and p16 (97%). While focal expression of MDM2 and p16 was observed in 14% and 67% of lipomas, respectively, no lipoma exhibited diffuse MDM2 positivity. In our hands, MDM2 expression by itself cannot exclude the diagnosis of AML or lipoma, and p16 alone is not helpful in separating AML and conventional lipoma from WDLS/DDLS. However, along with morphology, an immunohistochemical battery including HMB45, Melan-A, MDM2 and p16 are useful in distinguishing AML from WDLS/DDLS or lipoma. For equivocal cases, fluorescence in situ hybridization for MDM2 should be performed.

An 18-kg giant variant of a well-differentiated retroperitoneal liposarcoma of the kidney

Well-differentiated liposarcoma (WDLS), the most common type of liposarcoma is a slow growing, painless tumor usually located in the retroperitoneum or the limbs. In this abstract we present a case of a 71-year-old male who presented in our clinic with a diagnosis of a giant WDLS. We performed a CT scan from which we found a giant abdominopelvic mass originating from the right kidney. This mass was pushing almost all organs and structures from the right abdominal cavity across the midline to the left side, which includes the IVC, aorta and the right ureter, all bowels were also pushed and were above this mass. A large 18-kg fibro-fatty mass was extirpated. The histopathological findings reported low-grade differentiated liposarcoma. The CT scan, which was done 3 months after the operation, determined that the patient was free from recurrence.