A novel HMGA2::KITLG fusion in a dedifferentiated liposarcoma with amplification of MDM2 and HMGA2.

High-mobility group AT-hook 2 (HMGA2) is rearranged in various types of mesenchymal tumors, particularly lipomas. HMGA2 is also co-amplified with mouse double minute 2 (MDM2) in well-differentiated liposarcoma/dedifferentiated liposarcoma (WDLPS/DDLPS). We report a case of relapsed DDLPS with a novel in-frame fusion between HMGA2 and KITLG, which encodes the ligand for KIT kinase, a critical protein involved in gametogenesis, hematopoiesis, and melanogenesis. The HMGA2 breakpoint is in intron 3, a commonly observed location for HMGA2 rearrangements, while the KITLG breakpoint is in intron 2, leading to a fusion protein that contains almost the entire coding sequence of KITLG. By immunohistochemical staining, tumor cells expressed KIT and showed phosphorylated MAPK, a major KIT downstream target. We suggest an oncogenic mechanism that involves the overexpression of KITLG caused by its rearrangement with HMGA2, leading to the constitutive activation of KIT kinase. While MDM2 amplification was observed in both the primary tumor and the relapsed tumor, the HMGA2::KITLG was only present in the relapsed tumor, indicating the role of HMGA2::KITLG in disease progression.

Atypical Spindle Cell/Pleomorphic Lipomatous Tumor With Sarcomatous Transformation: Clinicopathologic and Molecular Analysis of 4 Cases.

Atypical spindle cell/pleomorphic lipomatous tumor (ASPLT) is a recently described adipocytic tumor predominantly affecting the subcutaneous soft tissues of adults. Previous studies have shown that ASPLT follows a benign clinical course with a 4% to 12% local recurrence rate and no risk of dedifferentiation. Herein, we describe the clinicopathologic and molecular findings of 4 cases of ASPLT showing unequivocal sarcomatous transformation. Three patients were male and one was female, aged 65, 70, 74, and 78 years. Two cases presented as mass-forming lesions, while 1 case was incidentally discovered. The tumors measured 30, 55, 80, and 110 mm and occurred in the chest wall (n = 2) or arm (n = 2); all were subcutaneous. Microscopically, they showed a biphasic appearance comprising a low-grade ASPLT component and a high-grade sarcomatous component. The low-grade components showed features in the spectrum of either atypical pleomorphic lipomatous tumor (n = 2) or atypical spindle cell lipomatous tumor (n = 2). The high-grade components displayed leiomyosarcoma-like (n = 2), pleomorphic liposarcoma-like (n = 1) or undifferentiated sarcoma-like (n = 1) morphology. On immunohistochemistry, tumors were negative for MDM2 and showed loss of RB1 expression. In addition, the leiomyosarcoma-like areas seen in 2 cases were positive for smooth muscle actin and H-caldesmon. Single-nucleotide polymorphism array, performed in 3 cases, showed deletions of TP53, RB1, and flanking genes in both components. In contrast, the sarcomatous components showed more complex genomic profiles with rare segmental gains and recurrent loss of PTEN (n = 3), ATM (n = 2), and CDKN2A/B (n = 2) among other genes. Whole exome sequencing identified a TP53 variant in one case and an ATRX variant in another, each occurring in both tumor components. Limited clinical follow-up showed no recurrence or metastasis after 1 to 13 months (median, 7.5 months) postsurgical excision. Altogether, our data support that ASPLT can rarely develop sarcomatous transformation and offer insights into the molecular mechanisms underlying this event.

Lingual neoplasia in nonhuman primates: Description of five cases and a literature review.

BACKGROUND: Documentation of lingual tumors is scarce in nonhuman primates. METHODS: Through a multi-institutional retrospective study we compile cases of primary and metastatic neoplasia in non-human primates. RESULTS: We describe five cases of lingual neoplasia. Three cases are primary lingual tumors: chondro-osteoblastic lipoma in a howler monkey, squamous cell carcinoma, and fibroma in two baboons. We describe two cases of metastatic lymphoma in the tongue in rhesus macaques. A literature review of published lingual neoplasia in nonhuman primates is included in this manuscript. CONCLUSION: Lingual neoplasia is seldom reported in non-human primates.

A case of Wilson's disease combined with intracranial lipoma and dysplasia of the corpus callosum with review of the literature.

BACKGROUND: Wilson's disease (WD) is an inherited disorder of copper metabolism. Agenesis of the corpus callosum is the complete or partial absence of the major united fiber bundles connecting the cerebral hemispheres. Intracranial lipoma is an adipose tissue tumor resulting from an abnormal embryonic development of the central nervous system. The simultaneous occurrence of these three disorders is rare and has not been reported. This report focuses on the pathogenesis and association between the three disorders and highlights the importance of recognizing and effectively managing their coexistence. CASE PRESENTATION: The purpose of this study was to present a patient with coexisting WD, intracranial lipoma, and corpus callosum dysplasia. We reviewed a female patient hospitalized in 2023 with clinical manifestations of elevated aminotransferases and decreased ceruloplasmin, as well as genetic testing for an initial diagnosis of Wilson's disease. Subsequently, a cranial MRI showed corpus callosum dysplasia with short T1 signal changes in the cerebral falx, leading to a final diagnosis of Wilson's disease combined with intracranial lipoma and corpus callosum dysplasia. The patient's WD is currently stable after treatment with sodium dimercaptosulfonamide (DMPS) and penicillamine, and the patient's abnormal copper metabolism may promote the growth of intracranial lipoma. CONCLUSION: The pathogenesis of WD combined with intracranial lipoma and corpus callosum dysplasia is complex and clinically rare. The growth of intracranial lipomas may be associated with abnormal copper metabolism in WD. Abnormal copper metabolism affects lipid metabolism and triggers inflammatory responses. Therefore, early diagnosis and treatment are beneficial for improvement. Each new case of this rare co-morbidity is important as it allows for a better assessment and understanding of these cases' more characteristic clinical manifestations, which can help estimate the course of the disease and possible therapeutic options.

Radiologic-histopathologic correlation of fatty island sign with fat necrosis in atypical lipomatous tumor and lipoma.

AIM: This study aimed to assess the imaging features of atypical lipomatous tumors (ALTs) and lipoma with fat necrosis. METHODS: This study included patients with histopathologically proven fat necrosis within adipocytic tumors who underwent preoperative imaging. Magnetic resonance imaging (MRI) and/or computer tomography (CT) findings of fat necrosis associated with lipomatous tumors were retrospectively reviewed, emphasizing the "fatty island sign (FIS)." FISs were defined as well-demarcated, focal fat-containing areas surrounded by more thickened septa compared with other intratumoral septa. Imaging findings of FIS were compared between ALT and lipoma. RESULTS: Fat necrosis was histopathologically confirmed in 17 patients (6 ALTs and 11 lipomas). Among them, 18 FISs were observed in 10 lesions (59%). Multiple FISs within a lesion were observed in 4 (40%) patients. The median maximum diameter of the FISs was 37 mm. Hypointense areas within FISs relative to the subcutaneous fat on T1- and T2-weighted images were observed in 8 (80%) and 9 (90%), respectively, whereas hyperintense areas within FISs on fat-suppressed T2-weighted images were observed in 2 (20%). Nonfatty solid components within FISs were observed in 2 (20%). On CT, increased fat attenuation and pure fat attenuation within FISs were observed in 6 (86%) and 1 (14%), respectively. The imaging findings of FIS were not significantly different between ALT and lipoma. CONCLUSION: FISs were observed in 59% of the histologically proven ALT and lipoma patients with fat necrosis. The hypointense areas relative to the subcutaneous fat on T1- and T2-weighted images and increased fat attenuation on CT were usually observed within FISs.

Melanocytic Nevus With Spindle Cell Lipomatous Metaplasia.

ABSTRACT: Melanocytic nevi can show a great number of morphological, cytoarchitectural, and stromal variations. Some of these histopathological patterns, infrequent or unusual, can occasionally produce diagnostic doubts or problems. A 22-year-old female patient presented a poorly pigmented cutaneous polypoid lesion of the scalp. Histopathological examination showed an intradermal melanocytic nevus composed of aggregates, nests, and cords of benign melanocytes, with collagenous stroma and large lipomatous areas. In the lipidized portion of the lesion, nevus cells, arranged in clusters, nests, and cords, were intimately associated with mature-appearing adipocytes, CD34-positive spindle cells, Alcian Blue-positive fibromyxoid stroma, and eosinophilic collagen bundles, findings resembling those typically seen in spindle cell lipoma. Spindle cell lipomatous metaplasia, rarely observed in some benign nonmelanocytic skin lesions, can be considered an additional unusual, not previously described, stromal variation occurring in melanocytic nevi.

Superficial Atypical Lipomatous Tumor With Pleomorphic Features: Case Report and Discussion of the Literature.

ABSTRACT: Among liposarcomas, well-differentiated liposarcoma and dedifferentiated liposarcoma are the most common. The majority of these tumors are found in deep retroperitoneum or extremities. When found outside the retroperitoneum, these adipose-derived tumors are known as atypical lipomatous tumors (ALT). Superficial ALT are particularly rare; thus, little is known about their clinical presentation, genomic status, and management. Here, we present the case of a 54-year-old man with an intermittently bothersome, slowly growing mass on his left upper back for over 2 years, which was incidentally diagnosed as ALT. This patient's ALT, however, showed a profound degree of pleomorphism with MDM2 and control centromere 12 (CEP12) coamplification and negative CD34 and S100 and RB1 expression, unlike most other ALT described in the literature. This case report details the diagnostic workup and histopathological findings for adipose tumors and summarizes the different subtypes, including atypical spindle cell/pleomorphic lipomatous tumor, pleomorphic liposarcoma, and spindle cell/pleomorphic lipoma, with brief discussion on management.

Orbital Liposarcoma: A Surveillance, Epidemiology and End Results Database Study.

PURPOSE: Orbital liposarcoma is a challenging tumor to treat due to its rarity and high rate of local recurrence, and the role of radiotherapy and chemotherapy remain unclear. Analysis of big data may improve our overall understanding of orbital disease and role of adjuvant therapies. METHODS: Data were extracted from the Surveillance, Epidemiology and End Results (SEER) Research Plus database from 1975 to 2017. All patients with a diagnosis of liposarcoma (ICD-O3 codes 8850-8858, 8869-8862, 8870, 8880, 8881) were included. Cases were divided into 4 groups by primary site: orbit, retroperitoneum, soft tissue, and other. RESULTS: A total of 16,958 patients were included. Patients with orbital involvement were younger and more likely to be female ( p < 0.05). Among orbital lesions, myxoid liposarcoma was the most common histologic subtype (6/19; 31.6%) followed by well differentiated (5/19; 26.3%). This differed from the distribution of histologic subtypes encountered elsewhere, for which well-differentiated liposarcoma was the most common (retroperitoneum 979/3,136; 31%, soft tissue 3,493/11,671; 30%, and other sites 497/2,132; 23%, p < 0.05). Dedifferentiated histologic subtype was the second most common subtype found in the retroperitoneum (946/3,136; 30%), whereas it was less common in the orbit (2/19; 11%) and soft tissue (1,396/11,671; 12%) ( p < 0.001). Patients with orbital liposarcoma had similar disease-specific mortality compared with soft-tissue location ( p = 0.825) and lower disease-specific mortality compared with retroperitoneal location ( p < 0.001). When all locations were combined, patients with well-differentiated liposarcoma had the lowest disease-specific mortality. CONCLUSIONS: Patients with orbital liposarcoma tend to be younger, female, and have a better prognosis than those with retroperitoneal disease, likely due to the lower incidence of dedifferentiated histologic subtype.

MDM4 amplification in atypical lipomatous tumors/well-differentiated liposarcoma: Private event or alternative oncogenic mechanism?

Adipocytic tumors are the most common mesenchymal tumors in soft tissues. Among them, a diagnostic challenge relies in the distinction between lipoma and atypical lipomatous tumor (ALT)/well differentiated liposarcoma (WDLPS), as both entities are often undistinguishable not only from a radiological point of view, but also at the microscopic level and particularly when dealing with small tumor specimen. Thus, detection of recurrent MDM2 amplifications may be the only criteria to discriminate malignant tumors from lipomas. In this study, we report the case of a patient diagnosed with a well differentiated, adipocytic tumor located in the inferior limb and lacking MDM2 amplification, whose diagnosis was reclassified for ALT/WDLPS after identification of an alternative MDM4 amplification by comparative genomic hybridization profiling, whole exome sequencing and fluorescence in situ hybridization (FISH). Screening of a cohort of 37 large, deep-seated, well-differentiated adipocytic tumors previously classified as lipomas using RT-qPCR and FISH failed to detect other cases of MDM4-amplified ALT/WDLPS. This report shows that MDM4 amplification is an exceptional molecular event alternative to MDM2 amplification in ALT/WDLPS. This alteration should be considered and looked for in suspicious adipocytic tumors to optimize their surgical management.

Ultrasonographic features of a gastric submucosal lipoma in a cat: A case study.

A 7-year-old Korean shorthair cat was admitted to our hospital with chronic constipation. Abdominal ultrasonography incidentally revealed a focal asymmetric gastric mass. The mass was submucosal and hypoechoic without loss of wall layering. Histopathological examination revealed a gastric submucosal lipoma (GSL). Although there have been reports of gastric submucosal fat infiltration in cats, there have been no reports regarding GSL. To our knowledge, this is the first report describing the ultrasonographic characteristics of GSL in a cat. Gastric submucosal lipoma should be considered as a differential diagnosis when a focal hypoechoic submucosal mass without loss of wall layering in the stomach is observed on ultrasound images. Key clinical message: This case report describes the ultrasonographic characteristics of GSL in a cat and aims to provide useful information for the diagnosis of lipoma occurring in the feline gastrointestinal tract. The ultrasonographic features and histological results we describe should be helpful in diagnosing submucosal lipoma in cats with similar conditions.

Caractéristiques échographiques d'un lipome sous-muqueux gastrique chez un chat: une étude de casUn chat coréen à poil court âgé de 7 ans a été admis à notre hôpital pour constipation chronique. L'échographie abdominale a révélé de manière fortuite une masse gastrique focale asymétrique. La masse était dans la sousmuqueuse et hypoéchogène sans perte de stratification murale. L'examen histopathologique a révélé un lipome sous-mucosal gastrique (GSL). Bien qu'il y ait eu des rapports d'infiltration de graisse dans la sous-muqueuse gastrique chez le chat, aucun rapport n'a été signalé concernant le GSL. À notre connaissance, il s'agit du premier rapport décrivant les caractéristiques échographiques du GSL chez un chat. Le lipome sous-muqueux gastrique doit être envisagé comme diagnostic différentiel lorsqu'une masse sous-muqueuse hypoéchogène focale sans perte de stratification de la paroi de l'estomac est observée sur les images échographiques.Message clinique clé:Ce rapport de cas décrit les caractéristiques échographiques du GSL chez un chat et vise à fournir des informations utiles pour le diagnostic des lipomes survenant dans le tractus gastro-intestinal félin. Les caractéristiques échographiques et les résultats histologiques que nous décrivons devraient être utiles pour diagnostiquer le lipome sous-muqueux chez les chats présentant des conditions similaires.(Traduit par Dr Serge Messier).

Corrigendum: Spindle cell lipoma: a rare case report on the hallux.

The original article was published on February 15, 2024 and corrected on April 15, 2024.The revised version of the article corrects Figure 2. The changes appear in the revised online PDF copy of this article.

Spindle cell lipoma: a rare case report on the hallux.

Spindle cell lipomas are a rare type of lipoma usually presenting in middle-aged to older men, often located on the posterior neck or shoulder; presentation on the foot is exceptionally uncommon. We report a 24-year-old man with spindle cell lipomas on the hallux of his left foot. He experienced an uneventful recovery after excision of the mass. We discuss clinical, radiologic, and histopathologic features of spindle cell lipomas and we review the differential diagnosis at this anatomic site.

[Well-differentiated/dedifferentiated liposarcoma associated with myxoid-like morphology: a clinicopathological and molecular genetic characteristics analysis of 34 cases].

Objective: To investigate the clinicopathological and molecular genetic characteristics of well-differentiated/dedifferentiated liposarcoma (WDLPS/DDLPS) with myxoid-like morphology, and to distinguish them from myxofibrosarcoma (MFS) with similar morphology. Methods: Twenty-nine cases of myxoid-like liposarcoma and 5 cases of MFS were collected from Henan Provincial People's Hospital, Zhengzhou, China and the First Medical Center of PLA General Hospital, Beijing, China from January 2015 to March 2023. Relevant markers were detected using immunohistochemistry and fluorescence in situ hybridization (FISH). The literature was also reviewed. Results: There were 24 males and 10 females, with ages ranging from 41 to 73 years. The tumor sites included retroperitoneum (n=17), abdomen (n=9), lower limbs (n=5), scrotum (n=1), upper limb (n=1) and axilla (n=1). WDLPS was commonly seen as lipomatoid type (12 cases), while the dedifferentiated components of DDLPS included low-grade (13 cases) and high-grade (2 cases) morphology, with low-high grade myxofibrosarcoma, dermatofibrosarcoma protuberans, and low-grade fibrosarcoma structures. Twenty-nine liposarcomas had various proportions of myxoid-like morphology, while 16 showed various degrees of tumor necrosis. The myxoid-like component showed myxoid pleomorphic liposarcoma (MLPS)-like morphology, lobulated growth, characteristic slender, ramified capillary network,"chicken claw-like"morphology, mucus-rich stroma and lung edema-like morphology. Tumor cells were spindle and oval, with many variable vacuolar lipoblasts. MDM2 gene amplification was detected using FISH and present in all tested cases (29/29). DDIT3 break-apart mutation was not detected, but its cluster amplification was present (24/29). Among the MFS cases, one showed cluster amplification (1/5), but no cases showed break-apart or amplification of MDM2 gene. Conclusions: WDLPS/DDLPS with myxoid-like morphology is most commonly seen in the retroperitoneum and abdominal cavity and mostly harbors DDIT3 break-apart probe amplification, while this amplification is not specific to liposarcoma. For core biopsy specimens or very rare tumors in the limbs, when histology has mucinous stroma and MLPS-like morphology, misdiagnosis of MLPS or other non-lipomatous neoplasms with myxoid morphology should be avoided.

[Giant cervical lipoma adjacent to carotid artery: a case report and literature review]. / Gigantskaya lipoma shei, prilezhashchaya k sonnoi arterii: klinicheskii sluchai i obzor literatury.

BACKGROUND: Cervical lipomas accompanied by neurovascular compression are extremely rare and require surgical treatment in case of appropriate symptoms. The preferable method is gross total resection, as otherwise they tend to recur. Invasive growth is not typical for lipomas. However, large tumors can involve adjacent nerves and vessels and significantly complicate resection. MATERIAL AND METHODS: We present a 57-year-old patient who underwent resection of giant soft tissue cervical lipoma invading neurovascular bundle and compressing the oropharynx and esophagus with dysphagia and positional asphyxia. The patient was followed-up for previous 5 years. Resection was necessary due to tumor enlargement with appropriate symptoms. Searching for literature data was performed in the Pubmed, Medline, EMBASE, Cochrane Library and eLibrary databases. RESULTS AND DISCUSSION: Gross total resection of 7-cm tumor was accompanied by mobilization of hypoglossal and vagus nerves, common, external and internal carotid arteries and jugular vein with repositioning of the oropharynx and esophagus. There was mild Horner's syndrome in early postoperative period. The patient was discharged in 4 days after surgery with regression of complaints. We found only 5 reports describing giant cervical lipomas invading neurovascular bundle. CONCLUSION: Giant cervical lipomas are extremely rare, and total resection with preservation of critical structures is possible in a specialized hospital.

Lipoblastoma-Like Tumor and Fibrosarcoma-Like Lipomatous Neoplasm Represent the Same Entity: A Clinicopathologic and Molecular Genetic Study of 23 Cases Occurring in Both Men and Women at Diverse Locations.

Lipoblastoma-like tumor (LLT) is a benign soft tissue tumor demonstrating mixed morphologic features of lipoblastoma, myxoid liposarcoma, and spindle cell lipoma but lacking genetic alterations associated with those tumors. LLT was originally thought to be specific to the vulva but has since been reported in the paratesticular region. The morphologic features of LLT overlap with those of "fibrosarcoma-like lipomatous neoplasm" (FLLN), a rare, indolent adipocytic neoplasm considered by some to form part of the spectrum of atypical spindle cell and pleomorphic lipomatous tumor. We compared the morphologic, immunohistochemical, and genetic features of 23 tumors previously classified as LLT (n = 17) and FLLN (n = 6). The 23 tumors occurred in 13 women and 10 men (mean age, 42 years; range, 17 to 80 years). Eighteen (78%) cases arose in the inguinogenital region, whereas 5 tumors (22%) involved noninguinogenital soft tissue, including the flank (n = 1), shoulder (n = 1), foot (n = 1), forearm (n = 1), and chest wall (n = 1). Microscopically, the tumors were lobulated and septated, with variably collagenized fibromyxoid stroma, prominent thin-walled vessels, scattered univacuolated or bivacuolated lipoblasts, and a minor component of mature adipose tissue. Using immunohistochemistry, 5 tumors (42%) showed complete RB1 loss, with partial loss in 7 cases (58%). RNA sequencing, chromosomal microarray, and DNA next-generation sequencing study results were negative for significant alterations. There were no clinical, morphologic, immunohistochemical, or molecular genetic differences between cases previously classified as LLT or FLLN. Clinical follow-up (11 patients [48%]; range, 2-276 months; mean, 48.2 months) showed all patients were alive without disease, and only one patient had experienced a single local recurrence. We conclude that LLT and FLLN represent the same entity, for which "LLT" seems most appropriate. LLT may occur in either sex and any superficial soft tissue location. Careful morphologic study and appropriate ancillary testing should allow for the distinction of LLT from its potential mimics.

Intraosseous hibernoma: clinicopathologic and imaging analysis of 18 cases.

AIMS: Intraosseous hibernomas are rarely reported tumours with brown adipocytic differentiation of unknown aetiology, with only 38 cases documented in the literature. We sought to further characterise the clinicopathologic, imaging and molecular features of these tumours. METHODS AND RESULT: Eighteen cases were identified occurring in eight females and 10 males (median age = 65 years, range = 7-75). Imaging indication was cancer surveillance/staging in 11 patients and clinical concern for a metastasis was raised in 13 patients. The innominate bone (7), sacrum (5), mobile spine (4), humerus (1) and femur (1) were involved. Median tumour size was 1.5 cm (range = 0.8-3.8). Tumours were sclerotic (11), mixed sclerotic and lytic (4) or occult (1). Microscopically, tumours were composed of large polygonal cells with distinct cell membranes, finely vacuolated cytoplasm, central or paracentral small bland nuclei with prominent scalloping. Growth around trabecular bone was observed. Tumour cells were immunoreactive for S100 protein (15/15) and adipophilin (5/5), while negative for keratin AE1/AE3(/PCK26) (0/14) and brachyury (0/2). Chromosomal microarray analysis, performed on four cases, did not show clinically significant copy number variation across the genome or on 11q, the site of AIP and MEN1. CONCLUSION: Analysis of 18 cases of intraosseous hibernoma, to our knowledge, the largest series to date, revealed that these tumours are most often detected in the spine and pelvis of older adults. Tumours were generally small, sclerotic and frequently found incidentally and can raise concern for metastasis. Whether or not these tumours are related to soft tissue hibernomas is uncertain.

Diagnostic accuracy of CT and MR features for detecting atypical lipomatous tumors and malignant liposarcomas: a systematic review and meta-analysis.

OBJECTIVES: This systematic review and meta-analysis evaluated the diagnostic accuracy of CT and MRI for differentiating atypical lipomatous tumors and malignant liposarcomas from benign lipomatous lesions. METHODS: MEDLINE, EMBASE, Scopus, the Cochrane Library, and the gray literature from inception to January 2022 were systematically evaluated. Original studies with > 5 patients evaluating the accuracy of CT and/or MRI for detecting liposarcomas with a histopathological reference standard were included. Meta-analysis was performed using a bivariate mixed-effects regression model. Risk of bias was evaluated using Quality Assessment of Diagnostic Accuracy Studies 2 (QUADAS-2). This study is registered on PROSPERO, number CRD42022306479. RESULTS: Twenty-six studies with a total of 2613 patients were included. Mean/median reported patient ages ranged between 50 and 63 years. The summary sensitivity and specificity of radiologist gestalt for detecting liposarcomas was 85% (79-90% 95% CI) and 63% (52-72%), respectively. Deep depth to fascia, thickened septations, enhancing components, and lesion size (≥ 10 cm) all demonstrated sensitivities ≥ 85%. Other imaging characteristics including heterogenous/amorphous signal intensity, irregular tumor margin, and nodules present demonstrated lower sensitivities ranging from 43 to 65%. Inter-reader reliability for radiologist gestalt within studies ranged from fair to substantial (k = 0.23-0.7). Risk of bias was predominantly mixed for patient selection, low for index test and reference standard, and unclear for flow and timing. CONCLUSION: Higher sensitivities for detecting liposarcomas were achieved with radiologist gestalt, deep depth to fascia, thickened septations, enhancing components, and large size. Combined clinical and imaging scoring and/or radiomics both show promise for optimal performance, though require further analysis with prospective study designs. CLINICAL RELEVANCE: This pooled analysis evaluates the accuracy of CT and MRI for detecting atypical lipomatous tumors and malignant liposarcomas. Radiologist gestalt, deep depth to fascia, thickened septations, enhancing components, and large size demonstrate the highest overall sensitivities. KEY POINTS: • The summary sensitivity and specificity of radiologist gestalt for detecting liposarcomas was 85% (79-90% 95% CI) and 63% (52-72%), respectively. • Radiologist gestalt, deep depth to fascia, thickened septations, enhancing components, and large tumor size (≥ 10 cm) showed the highest sensitivities for detecting atypical lipomatous tumors/well-differentiated liposarcomas and malignant liposarcomas. • A combined clinical and imaging scoring system and/or radiomics is likely to provide the best overall diagnostic accuracy, although currently proposed scoring systems and radiomic feature analysis require further study with prospective study designs.

Extramammary myofibroblastoma of the oral cavity.

Myofibroblastoma is a rare, benign mesenchymal tumor first described as a neoplasm of the breast. Extramammary myofibroblastoma is a histopathologically and genetically identical lesion occurring outside the breast. Herein is presented a case of extramammary myofibroblastoma arising in the oral cavity. A 59-year-old woman presented with a 1.5 cm nodule on the buccal surface of the lower lip. Wide local excision was performed. Histopathologic examination revealed haphazard fascicles of monomorphic spindle cells with hyalinized collagen bundles without fat. The spindled cells were diffusely positive for CD34, and focally for progesterone receptor. Desmin, smooth muscle actin, estrogen receptor, androgen receptor, S100, and STAT6 were negative. Rb1 expression was lost in tumor cells. Thus, the diagnosis of extramammary myofibroblastoma was made. Differential diagnoses include spindle-cell lipoma and angiofibroma. All three tumors are members of the 13q14 deletion/RB1 loss family. Indolent but locally aggressive (solitary fibrous tumor, desmoid fibromatosis) and frankly malignant (low-grade peripheral nerve sheath tumor, dermatofibrosarcoma protuberans) entities can be excluded by immunohistochemistry and careful microscopic examination. Extensive sampling extramammary myofibroblastoma is important to exclude the possibility of malignancy. Clinicians and pathologists alike should be aware of this entity and its potential to arise rarely in unusual locations.

Adipose and lipoma stem cells: A donor-matched comparison.

Lipomas are slow growing benign fat tumors that develop in soft tissues of the mesoderm. Thus, the specific (dys-)function of mesenchymal stem cells (MSCs) has been suggested in the development of lipomas, but details of the tumor pathogenesis remain unclear. Existing studies comparing stem cells from native adipose (adipose stem cells [ASCs]) and lipomatous tissues (LSCs) have reported contradicting findings. However, harvesting ASCs and LSCs from different individuals might have influenced proper comparison. Therefore, we aimed to characterize donor-matched ASCs and LSCs to investigate metabolic activity, proliferation, capability for tri-linear differentiation (chondrogenesis, adipogenesis, osteogenesis), and the secretome of mature adipocytes and lipomacytes. Both stem cell types did not differ in metabolic activity, but ASCs demonstrated stronger proliferation than LSCs. While there was no difference in proteoglycan accumulation during chondrogenic differentiation, adipogenesis was higher in ASCs, with more lipid vacuole formation. Conversely, LSCs showed increased osteogenesis by higher calcium deposition. Lipomacytes showed stronger secretory activity and released higher levels of certain adipokines. Our findings indicated that LSCs possessed important characteristics of MSCs, including ASCs. However, LSCs' low proliferation and adipogenic differentiation behavior did not appear to account for enhanced tissue proliferation, but the secretome of lipomacytes could contribute to lipomatous neoplasm.

Spindle Cell Lipoma With Florid Primary Follicular Lymphocytic Hyperplasia: A Novel Association With Potential Diagnostic Pitfalls.

ABSTRACT: Spindle cell lipoma (SCL) is a benign subcutaneous lipomatous neoplasm with a heterogeneous histologic appearance that varies greatly depending on the amount of fat, collagen, and myxoid stroma, which define the multiple subtypes of SCL, such as fat poor SCL, pseudoangiomatous SCL, and dendritic fibromyxolipoma. Cutaneous lymphoid hyperplasia is a spectrum of benign conditions characterized by reactive B-cell and T-cell cutaneous lymphocytic infiltrates. Cutaneous B-cell lymphoid hyperplasia is a heterogeneous group of non-neoplastic conditions that can be observed as reactive phenomena to infections, medications, allergens, or neoplasms and must be distinguished from cutaneous B-cell lymphomas. Here, we report a novel case of spindle cell lipoma, associated with B-cell primary lymphoid follicular hyperplasia, mixed within the tumor in a peculiar pattern, while discussing potential diagnostic pitfalls with low-grade B-cell lymphomas. This is the first report of such association in the literature.