Update on Lipomatous Tumors with Emphasis on Emerging Entities, Unusual Anatomic Sites, and Variant Histologic Patterns

An Atypical Case of Bladder Lipoma Presenting as Gross Hematuria: A Case Report

While conventional lipomas represent the most commonly seen benign mesenchymal tumor in adults, their occurrence in the bladder wall is exceptionally rare. This report details a rare case of a bladder lipoma, a benign tumor primarily composed of mature adipocytes, presenting as gross hematuria in a 68-year-old male. Despite the patient's previous history of left nephrectomy, no significant pathological findings were initially observed. The bladder lipoma was detected via cystoscopy as a polypoid mass on the posterior bladder wall and confirmed through transurethral resection of the bladder tumor (TUR-BT). Histopathological analysis verified the mass as a bladder lipoma composed of mature adipocytes. Following a specific postoperative follow-up period, no recurrence of the tumor was observed, suggesting successful treatment. This case underscores the clinical significance of considering bladder lipoma in differential diagnoses of bladder tumors, especially in patients presenting with gross hematuria, given its exceptional rarity.

An Intradermal Spindle Cell Lipoma on the Plantar Hallux in a Patient With Scleroderma and Ehlers-Danlos Syndrome: A Case Report

Spindle cell lipoma (SCL) is a rare variant of lipomas, which predominantly occurs in the regions of shoulder and posterior neck but rarely on the toes. Epidemiological studies have demonstrated increased incidence of cancers in patients with scleroderma. A 28-year-old female with scleroderma and Ehlers-Danlos syndrome developed a painful, skin colored, raised, polypoid lesion on the plantar side of the left hallux for several years. The lesion was surgically excised. Pathological evaluation showed intradermal bland spindle cells associated with delicate ropey/refractile collagen bundles with strong and diffuse cytoplasmic expression of CD34 but negative expression of Rb and S-100, which are consistent with SCL. We report a first case of SCL on the plantar hallux in a young female patient with scleroderma and Ehlers-Danlos disease with clinical presentations, histopathology, and treatment to raise awareness of clinicians to this rare variant of lipomas.

Retroperitoneal Dedifferentiated Liposarcoma

OBJECTIVES

We aimed to test the hypothesis that in retroperitoneal dedifferentiated liposarcoma (DDLS) the presence of the dedifferentiated (DD) component at the resection margin is associated with adverse outcome.

METHODS

We retrospectively searched the archive for primary resections of retroperitoneal DDLS performed at our institution between 1990 and 2017. Slides were rereviewed for diagnosis, Fédération Nationale des Centres de Lutte Contre le Cancer grade, myogenic differentiation, and the presence of the well-differentiated (WD) or DD component at the resection margin. The medical records were reviewed for patient age, sex, tumor size, tumor focality, adjuvant/neoadjuvant therapy, local recurrence, distant metastases, local recurrence-free survival (LRFS), overall survival (OS), and follow-up duration.

RESULTS

The presence of the DD component at the resection margin was associated with worse LRFS compared with cases without the DD component at the margin (P = .002). However, OS was not significantly affected (P = .11).

CONCLUSIONS

LRFS is significantly shorter in cases with the DD component at the margin compared with cases without DD tumor at the margin, while there is no association with OS. We recommend reporting the presence or absence of DD tumor at the margin in retroperitoneal DDLS, as it adds meaningful prognostic information.

Spindle cell lipoma, dorsum of hand in a 4 year old child: A rare entity

Lipogenic tumors are an uncommon entity in children. There are several variants of lipoma, of which spindle cell lipoma is an extremely rare and accounts for only 1.5% of all lipoma diagnosis. Spindle cell lipoma rarely involves distal extremities. We report a 4-year old boy with swelling over dorsum of hand operated for aesthetic purposes. The report also highlights the salient cytological features, which can help differentiate this entity from other closer mimics on aspiration cytology, guiding the surgeon for appropriate management.

Reduced lipolysis in lipoma phenocopies lipid accumulation in obesity

BACKGROUND

Elucidation of lipid metabolism and accumulation mechanisms is of paramount importance to understanding obesity and unveiling therapeutic targets. In vitro cell models have been extensively used for these purposes, yet, they do not entirely reflect the in vivo setup. Conventional lipomas, characterized by the presence of mature adipocytes and increased adipogenesis, could overcome the drawbacks of cell cultures. Also, they have the unique advantage of easily accessible matched controls in the form of subcutaneous adipose tissue (SAT) from the same individual. We aimed to determine whether lipomas are a good model to understand lipid accumulation.

METHODS

We histologically compared lipomas and control SAT, followed by assessment of the lipidome using high-resolution ¹H NMR spectroscopy and ESI-IT mass spectrometry. RNA-sequencing was used to obtain the transcriptome of lipomas and the matched SAT.

RESULTS

We found a significant increase of small-size (maximal axis < 70 µm) and very big (maximal axis > 150 µm) adipocytes within lipomas. This suggests both enhanced adipocyte proliferation and increased lipid accumulation. We further show that there is no significant change in the lipid composition compared to matched SAT. To better delineate the pathophysiology of lipid accumulation, we considered two groups with different genetic backgrounds: (1) lipomas with HMGA2 fusions and (2) without gene fusions. To reduce the search space for genes that are relevant for lipid pathophysiology, we focused on the overlapping differentially expressed (DE) genes between the two groups. Gene Ontology analysis revealed that DE genes are enriched in pathways related to lipid accumulation.

CONCLUSIONS

We show that the common shared lipid accumulation mechanism in lipoma is a reduction in lipolysis, with most gene dysregulations leading to a reduced cAMP in the adipocyte. Superficial lipomas could thus be used as a model for lipid accumulation through altered lipolysis as found in obese patients.

Atypical Lipomatous Tumor/Well-Differentiated Liposarcoma With Features Mimicking Spindle Cell Lipoma

Atypical lipomatous tumor/well-differentiated liposarcoma (ALT/WDL) and spindle cell lipoma are lipomatous tumors with distinct clinical, molecular, and prognostic features. Although histological and immunophenotypic features can overlap between ALT/WDL and spindle cell lipoma, the oncogenesis and clinical behavior are markedly different. In borderline cases, molecular analysis for MDM2 or CDK4 amplification can aid in distinguishing ALT/WDL from spindle cell lipoma. Although dedifferentiated liposarcoma has been reported to harbor both MDM2 amplification and loss of the RB1 region, we are not aware of a reported RB1 loss in well-differentiated ALT/WDL. In this article, we present a 69-year-old woman with a lipomatous tumor in the gluteal region that histologically, immunohistochemically, and molecularly mimicked spindle cell lipoma (with positive immunohistochemical staining for CD34 and loss of the RB1 gene region), yet harbored amplification of MDM2 and CDK4 confirmed by fluorescence in situ hybridization, supporting classification as ALT/WDL. This case strengthens the argument that in atypical clinical contexts, molecular studies for MDM2/CDK4 should be considered in tumors resembling spindle cell lipoma.

Investigation of stemness and multipotency of equine adipose-derived mesenchymal stem cells (ASCs) from different fat sources in comparison with lipoma

BACKGROUND

Adipose tissue-derived mesenchymal stem cells (ASCs) offer a promising cell source for therapeutic applications in musculoskeletal disorders. The appropriate selection of ASCs from various fat depots for cell-based therapy is challenging. The present study aims to compare stemness and multipotency of ASCs derived from retroperitoneal (RP), subcutaneous (SC), and lipoma (LP) fat to assess their usefulness for clinical application.

METHODS

Equine ASCs from the three fat tissue sources were isolated and characterized. The cell viability, proliferation, and self-renewal were evaluated using MTT, sulforhodamine B, and colony forming unit (CFU) assays. Stem cell relative marker CD44, CD90, and CD105 and tumor marker CA9 and osteopontin (OPN) expression were quantified using RT-qPCR. Multipotency of ASCs for adipogenic, osteogenic, and chondrogenic differentiation was examined by quantifying Oil Red O and Alizarin Red S staining, alkaline phosphatase activity (ALP), and expression of differentiation relative markers. All data were statistically analyzed using ANOVA.

RESULTS

RP fat-derived ASCs showed a higher cell proliferation rate compared to SC and LP derived cells. In contrast, ASCs from lipoma displayed a lower proliferation rate and impaired CFU capacities. The expression of CD44, CD90, and CD105 was upregulated in RP and SC derived cells but not in LP cells. RP fat-derived cells displayed a higher adipogenic potential compared to SC and LP cells. Although ASCs from all fat sources showed enhanced ALP activity following osteogenic differentiation, SC fat-derived cells revealed upregulated ALP and bone morphogenetic protein-2 expression together with a higher calcium deposition. We found an enhanced chondrogenic potency of RP and SC fat-derived cells as shown by Alcian blue staining and upregulation of aggrecan (Aggre), cartilage oligomeric matrix protein precursor (COMP), and collagen 2a1 (Col2a1) expression compared to LP. The expression of OPN and CA9 was exclusively upregulated in the ASCs of LP.

CONCLUSIONS

The results provide evidence of variation in ASC performance not only between normal fat depots but also compared to LP cells which suggest a different molecular regulation controlling the cell fate. These data provided are useful when considering a source for cell replacement therapy in equine veterinary medicine.

Intraoral lipomas: A clinicopathological study of 43 cases, including four cases of spindle cell/pleomorphic subtype

BACKGROUND

The aim of this study was to describe the clinicopathological characteristics of 43 intraoral lipomas and classify them according to their microscopic variants.

MATERIAL AND METHODS

All the cases of intraoral lipomas diagnosed at an Oral Pathology service were selected for the study. Clinical data, such as age, gender, location, time of evolution, clinical presentation, clinical hypothesis of diagnosis, and treatment, were collected from the clinical files.

RESULTS

Of the 43 cases analyzed, 24 (55.8%) occurred in women. The mean age was 77.4 years. The most affected site was the buccal mucosa (22 cases, 51.1%). The mean lesion size was 1.7 cm. Twenty-three cases (53.5%) were classified as simple lipoma, 14 (32.6%) as fibrolipoma, four (9.3%) as spindle cell/pleomorphic lipoma (SC/PL), one (2.3%) as lipoma of the salivary glands, and one (2.3%) as intramuscular lipoma. In one case of SC/PLs, lipoblasts were observed. No atypical lipoblasts or mitoses were noted. Lipoma was considered more often than other tumor histological subtypes among the clinical hypotheses of diagnosis when the final diagnosis was simple lipoma (p=0.01).

CONCLUSIONS

Intraoral lipomas present different clinical presentation depending on the histological subtype. In SC/PLs, lipoblasts with vacuolated cytoplasm may be found and the presence of mature adipocytes is essential for diagnosis.