Demonstration of MDM2 amplification is currently recommended to confirm the diagnosis of well-differentiated adipocytic tumors arising in the retroperitoneum, abdomen, and pelvis; recurrent "lipomas"; those with equivocal cytologic atypia; deep extremity tumors >10cm which lack cytologic atypia and occur in patients >50years old, and in special clinical circumstances (Clay et al., 2015 [Clay criteria]). In our practice, fluorescence in situ hybridization studies (FISH) for MDM2 were historically performed for all referred-in testing requests, for all well-differentiated fatty tumors >10cm, and to confirm the diagnosis of atypical lipomatous tumor/well-differentiated liposarcoma (ALT/WDL) in cases with definite atypia. As part of a test utilization review, after exclusion of dedifferentiated liposarcoma, we reviewed 1151 ostensibly fatty tumors on which FISH was successfully performed. After exclusion of 203 cases for which testing was inappropriate or indicated for other reasons, 233/948 (24.6%) fatty tumors met at least one Clay criterion, and 222 (23.4%) had definite nuclear atypia. Among tumors with definite atypia, 152 (68.5%) were ALT/WDL, and 48 (21.6%) were spindle cell/pleomorphic lipoma arising in unusual locations or atypical spindle cell/pleomorphic lipomatous tumors. Thirty (12.9%) cases meeting any Clay criteria were ALT/WDL, and 4/453 (0.9%) tumors not meeting Clay criteria or having atypia were ALT/WDL. The sensitivity of Clay criteria plus nuclear atypia for ALT/WDL was 97.8%, while specificity was 62.7%. We conclude that it is safe to defer MDM2 FISH in well-differentiated fatty tumors not meeting Clay criteria and lacking nuclear atypia.

ABSTRACTSpindle cell lipomas (SCL) and pleomorphic lipomas (PL) are today considered a single tumor entity (SCLPL). Atypical SCLPL, in contrast, represents a recently recognized related but distinct entity. Here we explored the correlation between genomic features and morphological aspects of SCLPL and atypical SCLPL and the role of the RB1 gene in tumor development. Seventy‐one samples from 68 patients with SCLPL or atypical SCLPL, as well as a lipomatous tumor from a retinoblastoma patient with a germline pathogenic variant in the RB1 gene, and two pleomorphic liposarcomas were analyzed using chromosome banding, high‐resolution genomic arrays (SNP array), whole exome sequencing (WES), and/or RNA sequencing (RNA‐seq). Common for all tumors was involvement of 13q; other recurring variants were deletion of 16q, 6q, and 17p. A minimally deleted region that only contained RB1 was found on 13q. A distinction was seen between SCL on the one hand and PL and atypical SCLPL on the other; SCL had fewer copy number aberrations in general, and loss of 17p/TP53 gene or a SNV affecting TP53 was only rarely detected in SCL but seen in the vast majority of PL and atypical SCLPL tumors. Thus, at the molecular level, SCL is different from PL/atypical SCLPL. Furthermore, the finding of the same copy number changes (loss of 13q, 6q, 16q, and 17p) in some pleomorphic liposarcomas raises the possibility that a subset of SCLPL/atypical SCLPL have the potential for malignant transformation.

Lipoma and well-differentiated liposarcoma are clinically differentiated by site of origin and length, and pathologically differentiated by immunostaining with MDM2 and CDK4. An 82-year-old male patient. A retroperitoneal lipomatous tumor which compressed intraabdominal organs was found on CT and MRI scan. Laparotomy for retroperitoneal tumor resection was performed. Lipomatous tumor more than 10 cm was extirpated. The pathological diagnosis was retroperitoneal intramuscular lipoma. One year after surgery, there is no sign of tumor recurrence.

Intravascular lipomas are rare benign tumors composed of adipose tissue that originate from the walls of blood vessels. They most commonly arise from veins, are typically asymptomatic, and rarely occur in the lower extremities. When large, these tumors can cause symptoms related to venous obstruction, such as swelling and pain. We report a case of a 75-year-old man with an intravascular lipoma in the right common femoral vein, identified during evaluation of lower extremity swelling and poorly healing ulcers. Surgical resection was ultimately required. This case contributes to the few published reports of pathologically proven symptomatic intravascular lipomas involving the lower extremity veins. Comprehensive preoperative imaging played a critical role in characterizing the lesion. The case facilitates a discussion of key differential diagnoses, such as atypical lipomatous tumors/well-differentiated liposarcoma and leiomyosarcoma. · Intravascular lipomas are rare and generally asymptomatic masses that most often arise in the veins of the upper extremity and thorax.. · The differential diagnosis for a fatty intravascular mass includes benign lipoma, atypical lipomatous tumor (ALT)/well-differentiated liposarcoma, and leiomyosarcoma.. · Benign lipomas usually demonstrate homogeneous fat signal with thin fibrous septa and minimal nonadipose components.. · Imaging features suggestive of ALT/well-differentiated liposarcoma are reduced and/or heterogeneous fat composition, thickened septa, and nodular nonadipose tissue..

Intramuscular lipomas are rare benign soft tissue tumors that originate within skeletal muscle fibers and account for a small fraction of all lipoma cases. Their infiltrative growth pattern can pose diagnostic challenges, particularly in differentiating them from well-differentiated liposarcomas. We report a case of a 42-year-old male who presented with a painless, gradually enlarging mass over the lateral aspect of the left shoulder. Magnetic resonance imaging (MRI) revealed a well-defined intramuscular fatty lesion within the deltoid muscle, measuring 30 × 19 mm, consistent with a lipomatous tumor. The patient underwent complete surgical excision of the mass. Histopathological examination confirmed an infiltrating intramuscular lipoma composed of mature adipocytes without cellular atypia or malignancy. The postoperative recovery was uneventful, and no recurrence was observed during follow-up. This case highlights the importance of imaging and histological evaluation in distinguishing benign infiltrating lipomas from low-grade liposarcomas. Complete surgical excision remains the treatment of choice to prevent recurrence and ensure definitive diagnosis.

True lipomas involving the joints are rare. In this study, we investigated 18 intra-articular and juxta-articular lipomas of the knee. The tumor occurred in middle-aged or older patients (median age: 63years) with a strong female predilection (3 males and 15 females), and most presented with palpable masses without associated pain. Four tumors were entirely intra-articular, whereas 11 involved both intra-articular and extra-articular compartments, consistent with herniation from the joint. The herniation commonly occurred through the space between the patellar tendon and either the lateral or medial patellar retinaculum, with the extra-articular masses being located anterolaterally or anteromedially to the joint. All tumors analyzed at least focally involved or abutted the infrapatellar fat pad. The relationship with the joint was not recognized at diagnosis in most of the herniated cases. The remaining 3 were juxta-articular lipomas that were firmly fixed to the joint. All 18 lipomas revealed distinct histology, and included fine lobulation, fibrosis with spindle cells, conspicuous presence of medium-caliber vessels and slivers of dense, tendon-like fibrous tissue. Myxoid changes, chondro-osseous metaplasia, and fat necrosis were commonly observed. These findings led to a suspicion of atypical lipomatous tumors, other benign lipomatous tumors, malformation, or hamartoma, and originally prevented a definitive diagnosis in the majority of cases. HMGA2 immunoreactivity was observed in all 18 tumors, whereas all were negative for MDM2 expression and RB1 loss. RNA sequencing revealed HMGA2 fusions in 8 of the 12 tumors tested. Intra-articular and juxta-articular lipomas of the knee, particularly the herniated intra-articular subset, are likely under-recognized and can be a source of diagnostic concern because of peculiar histology and unawareness of the relationship with the joint.

Atypical lipomatous tumor is a well-differentiated liposarcoma which is locally aggressive but does not typically metastasize. Atypical lipoma of the forearm is a very rare condition with unknown incidence. The management of atypical lipoma of the forearm is controversial, with some authors suggesting en bloc excision of the tumor. We report a case of atypical lipoma of the forearm in a 36-year-old female treated by marginal excision. The patient had no evidence of recurrence in medium-term follow-up. We conclude that marginal excision is an accepted method for the management of atypical lipoma of the forearm, which has no evidence of neurovascular encroachment.

Angiomyxolipoma is an exceptionally rare variant of lipoma characterized by mature adipose tissue admixed with myxoid stroma and vascular elements. Herein, we report a rare case of infiltrative angiomyxolipoma in the neck region of a 55-year-old male. The swelling gradually increased over 18 months and was managed with surgical excision. Histopathology confirmed the diagnosis. The patient remains recurrence-free at 6 months. This report aims to highlight the diagnostic challenges and the importance of complete excision in managing such rare lipomatous tumors.

This study evaluated the diagnostic value of clinicopathological features and immunohistochemical markers for distinguishing lipomas from atypical lipomatous tumors/well-differentiated liposarcomas (ALT/WDLPS). An integrated diagnostic model for ALT/WDLPS was developed to guide diagnosis, treatment planning, and prognosis. This retrospective analysis included 216 patients with lipomatous tumors diagnosed between February 2018 and December 2024, including lipomas (n = 149), spindle cell lipomas (n = 3), ALTs/WDLPs (n = 62), and WDLPS with a low-grade de-differentiated component (n = 2). Immunohistochemical data for MDM2, CDK4, and p16 were available for 131 patients. MDM2 amplification was significantly more frequent in patients ≥ 55 years and in tumors of the lower limbs (the thigh) and retroperitoneum (p = 0.000). Larger tumor size and multiplicity were also associated with MDM2 amplification (p < 0.05). Immunohistochemistry sensitivities for ALT/WDLPS vs. lipomas: 65% (MDM2), 100% (CDK4), and 80.4% (p16); combined, the specificity was 100% and sensitivity 85.6%. The diagnostic model achieved 93.3% sensitivity and 72.2% specificity. Scores < 0.219 indicated a higher likelihood of lipoma, while scores > 0.652 indicated a higher likelihood of liposarcoma. Age ≥ 55 years, lower extremity/retroperitoneal location, tumor diameter ≥ 9.9 cm, and positive markers were independent risk factors. This model provides an effective tool for ALT/WDLPS identification.Supplementary InformationThe online version contains supplementary material available at 10.1038/s41598-025-22547-5.

Introduction: Primary cardiac sarcomas are exceedingly rare and aggressive malignancies, with limited epidemiological data due to their low incidence. This study aims to characterize the incidence trends of cardiac sarcomas over a 21-year period using a population-based cancer registry and to assess differences in incidence by sex. Methods: We conducted a retrospective cohort study using data from the Surveillance, Epidemiology, and End Results (SEER) Program, accessed through SEER*Stat software version 8.4.5. Eligible cases were identified using the International Classification of Diseases for Oncology (ICD-O-3) site code C38.0 (Heart) and histology codes corresponding to soft tissue tumors and sarcomas, including: NOS (8800–8809), fibromatous neoplasms (8810–8839), myxomatous neoplasms (8840–8849), lipomatous neoplasms (8850–8889), myomatous neoplasms (8890–8929), complex mixed and stromal neoplasms (8930–8999), synovial-like neoplasms (9040–9049), and blood vessel tumors (9120–9169). The study period spanned from 2000 to 2021. Only first primary tumors were included, and no duplicate cases were identified. Incidence rates were age-adjusted to the 2000 U.S. standard population and stratified by sex. Temporal trends were evaluated using joinpoint regression. Results: A total of 264 cases of primary cardiac sarcomas were identified between 2000 and 2021. The overall age-adjusted incidence rate remained relatively stable throughout the study period, with no significant annual percent change observed. Males demonstrated a higher incidence rate compared to females (0.0065 vs. 0.0053 per 100,000 person-years, respectively), but this difference did not reach statistical significance (p &gt; 0.05). There were no notable shifts in the incidence of specific sarcoma subtypes over time. Conclusion: This study provides one of the most comprehensive analyses of primary cardiac sarcoma incidence trends in the U.S. to date. Despite the rarity of this malignancy, the incidence has remained stable over the past two decades. While males appear to be more affected than females, the observed sex difference is not statistically significant. Continued surveillance and larger datasets are necessary to better understand risk factors and inform early detection strategies for this rare and often fatal disease.

Near-infrared lipid droplet polarity fluorescent probe based on phenothiazine derivative for diagnosis of non-alcoholic fatty liver and tumors.

Tumours of the ischiofemoral region: The largest case series.

Giant Omental Lipoma in a Child.

Soft tissue sarcomas are a heterogeneous group of connective tissue neoplasms with a low incidence. Myxoid liposarcoma is a rare subtype with a preferential location in the extremities. The gold standard of treatment is wide resection with negative margins for neoplasia. However, unusual locations have different clinical behavior, and their management is limited by a low level of evidence. A 65-year-old man with a lipomatous tumor in the inguinal region who, after marginal resection, showed evidence of myxoid liposarcoma with margins involved by neoplasia. Imaging studies revealed tumor in the inguinal region with retroperitoneal extension. A radical orchiectomy with en bloc resection of the tumor was performed with no evidence of neoplasia in the resected specimen. Close follow-up without adjuvant therapy was decided by a multidisciplinary committee. The approach to a rare soft tissue sarcoma in an unusual region is a challenge in oncological treatment and in the absence of high-quality evidence, the consensus of a multidisciplinary team is necessary to determine the best therapeutic option.

The identification of adipose tissue in endometrial biopsy or curettage specimens is an important yet rare histologic finding that may suggest uterine perforation, warranting careful pathologic evaluation to distinguish it from histologic mimickers. To assess the presence of adipose tissue in endometrial samples and evaluate its diagnostic challenges and clinical implications. A retrospective cohort study was performed on cases from an 8-year period in which adipose tissue was identified in endometrial biopsy or curettage specimens. Hematoxylin-eosin-stained sections were reviewed, and relevant clinical data, including postoperative outcomes, were analyzed. Twenty-three patients were included (mean age ± standard deviation, 60.6 ± 13.3 years); 18 of 23 patients (78.3%) underwent curettage. Endometrial polyp was the most common concurrent diagnosis (8 of 23; 34.8%). Uterine perforation was clinically identified intraoperatively in 6 cases (6 of 23; 26.1%), all managed without complications. Most samples (16 of 23; 69.6%) contained a small amount of adipose tissue (1%-25%). Common risk factors included fibroids (5 of 23; 21.74%); cervical stenosis, polyps, intrauterine synechiae (4 of 23; 17.39% each); and history of prior cesarean delivery (10 of 23; 43.48%). The mean interval to notify clinicians of the adipose finding was 2.79 ± 1.65 days. One patient developed a postoperative abscess, successfully treated with antibiotics. No significant associations were found between risk factors or adipose proportion and intraoperative detection or postoperative complications (all P ≥ .05). While adipose tissue in endometrial specimens may indicate uterine perforation, it was not associated with significant adverse outcomes in this cohort. Pathologists must remain vigilant, as benign mimics such as pseudolipomatosis or lipomatous tumors should be excluded during evaluation.

Abstract This case report describes a rare chondro‐osteoblastic lipoma identified in a 10‐year‐old, mixed‐breed, female dog that presented with a progressively enlarging mass on the left thoracic wall. Histopathological examination revealed a poorly circumscribed proliferation of mature adipocytes interspersed with areas of cartilaginous and osseous metaplasia. The lesion was completely excised, and no recurrence was observed during follow‐up. This case highlights the importance of considering this rare variant in the differential diagnosis of lipomatous tumours in dogs.

BackgroundAtypical lipomatous tumors (ALTs) are aggressive fat cell tumors that are distinguished from benign lipomas (SL) mainly through histopathology. Biopsy is needed for suspicious cases but can miss malignancy, so complete surgical removal and examination are essential. MRI is used but often can't differentiate ALT from SL. We introduce a machine learning method for tumor classification.PurposeTo characterize the classification performance of a Bayesian additive regression trees (BART) model, built from MR radiomic features, and compare it to the readings of a musculoskeletal radiologist in classifying atypical lipomatous tumors (ALTs) from simple lipomas.Materials and MethodsRetrospective data were collected from 5 medical institutions in North America, for a total of 437 patients; the mean age was 58 years ±12 years, with 248 men and 287 women. At each institution, at least T1-MRI images without contrast were collected from patients with suspected ALT prior to surgery. Histopathology was used as the reference standard. Radiomic features extracted from the MRI images were used to train the BART model and a random forest model for comparison of classification performance using a 10-fold cross-validation. Both models were compared with the classifications of an experienced (>10 years) musculoskeletal radiologist who scored the images on a 5-point scale.ResultsA cohort of 423 patients was included, and 1132 radiomic features were extracted from each MR study. The BART model had an accuracy, sensitivity, and specificity of 77.07% (72.76%-80.99%), 77.67% (71.36%-83.16%), and 76.50% (70.28%-81.97%), respectively, when utilizing all predictors and aggregating training and testing data from all the cohorts, approximating the human reader at 78.72% (74.51%-82.53%), 76.21% (69.80%-81.85%), and 81.11% (75.25%-86.09%), respectively. In the external validation, the average area under the curve (AUC) value across cohorts between the BART model and the human reader differed by 0.04 AUC points. From the receiver operating characteristic curve, the AUC was calculated to be 84.72% (81.00%-88.50%) and 84.74% (81.00%-88.50%) for the BART and human reader, respectively.ConclusionThis study demonstrated that the BART model can distinguish ALT from lipoma with diagnostic performance comparable to an experienced human observer.

Adrenal myelolipomas are lipomatous tumours containing myeloid cell elements that typically have a benign course. They account for 3.3-6.5% of all adrenal masses and are usually unilateral in 95% of cases. These tumours affect both sexes equally during midlife. While they are often asymptomatic, symptomatic cases may require surgery. The pathogenesis is believed to involve either metaplastic changes in mesenchymal cells or overstimulation by Adrenocorticotropic Hormone (ACTH). The present case involves a 49-year-old male who presented with abdominal pain and fullness lasting three months. Serum ACTH levels were within normal limits, with a mild elevation of 17-Hydroxyprogesterone (17-OHP). Radiological investigations, including both Ultrasonography (USG) and Computed Tomography (CT), described the lesion as a large, well-circumscribed, heterodense lesion in the left adrenal gland, which was identified as adrenal myelolipoma. Histopathological examination revealed a tumour comprised of adipocytes and extramedullary trilineage haematopoietic elements, confirming the diagnosis of adrenal myelolipoma. The significance of presenting this case lies in its large size, the definite clinical symptoms of abdominal pain and fullness, and the fact that it was unrelated to serum ACTH levels.

Abstract Colonic lipomas are rare, benign tumors of adipose tissue that typically remain clinically silent. However, large lipomas usually cause symptoms, including intussusception, obstruction, and bleeding. We present a case of a 78-year-old man with previously treated non-Hodgkin lymphoma who developed colo-colic intussusception secondary to a giant colonic lipoma. Contrast-enhanced computed tomography was suggestive of colo-colic intussusception, and emergency surgery confirmed a 30 × 8 cm pedunculated mass arising from the splenic flexure, with descending colon intussuscepting into the sigmoid colon along with the lesion. An adjacent small, 4 × 3 cm, similar lesion was also observed at the same site. The patient underwent a successful left hemicolectomy with anterior resection and transverse end colostomy, with an uneventful postoperative recovery. Histopathologic examination confirmed a submucosal lipoma measuring 15 × 9 × 6 cm. This case is notable for the exceptional size of the lipoma, the rare location at the splenic flexure, and the complex presentation and surgical management required. It emphasizes the necessity of including colonic fatty tumors in diagnostic considerations for elderly individuals presenting with abdominal discomfort and rectal hemorrhage, especially those with a history of prior malignant disease, while highlighting the diagnostic complexities and operative decision-making in similar presentations.

ABSTRACTAdult airway foreign bodies are misdiagnosed as endobronchial tumours on imaging. A 77‐year‐old man with asbestosis presented with a worsening cough. Computed tomography (CT) showed a 12‐mm low‐attenuation right upper‐lobe bronchial lesion with distal bronchiectasis and infiltrates. Magnetic resonance imaging (MRI) suggested a fat‐containing tumour (lipoma or hamartoma). Flexible bronchoscopy revealed a yellowish polypoid mass; poor sedation tolerance necessitated rigid bronchoscopy under general anaesthesia. Using a 1.7‐mm cryoprobe, the lesion was cryoactivated for 10 s and removed en bloc. It proved to be a foreign body resembling a legume and was later confirmed to be an aspirated soybean from 1 month earlier. The fat and water content of soybeans can yield MRI appearances similar to fatty tumours. Distinguishing tumours from foreign bodies by imaging or bronchoscopy alone is challenging. Cryoprobe extraction is effective for hydrated foreign bodies, and aspiration should be considered in the differential diagnosis of endobronchial tumours.