Imaging modality: Light microscopy of hematoxylin and eosin (H&E) stained formalin-fixed paraffin-embedded tissue section. Specimen: benign lipomatous lesion composed of mature adipocytes. Primary subject: adipose tissue within soft tissue (lipoma) with fibrous septa. Imaging perspective: histological cross-section through adipose lobules. The morphologic features: uniform round-to-oval adipocytes with small clear cytoplasm, peripherally placed nuclei, lacking significant cytologic atypia. Septa are relatively thin and occasionally show fibrous strands; no lipoblasts are evident. In this image, the background is comprised of many univacuolated adipocytes forming a lobulated architecture typical of lipoma. Compared to atypical lipomatous tumor/well-differentiated liposarcoma (ALT/WDL), this lesion shows minimal to no variation in adipocyte size, lack of hyperchromatic, atypical stromal cells in fibrous septa, and absence of necrosis or mitotic activity. Intramuscular lipoma variants may show atrophic skeletal muscle fibers adjacent to adipose tissue; in such cases, entrapped muscle fibers with hyperchromatic nuclei can mimic stromal atypia but lack lipoblasts and genetic alterations characteristic of WDL. The image corresponds to a benign lipomatous tumor and illustrates the core criteria used to distinguish lipoma from ALT/WDL in routine histopathology. Immunohistochemical or molecular markers, including MDM2 amplification status, can assist in differentiating ALT/WDL from benign lipomas in challenging cases. Accurate classification informs surgical margins and surveillance strategies.

Imaging modality: Light microscopy of an H&E stained tissue section from a subcutaneous adipose lesion. Specimen: Excisional biopsy tissue of soft tissue mass. Location: Subcutaneous adipose tissue within the extremities or trunk, consistent with hibernoma lipoma-like variant. Visual features: The slide shows abundant univacuolated mature adipocytes with clear lipid droplets, minimal cytoplasm, and nuclei at the periphery, creating a pale, foamy appearance. The adipocytes are arranged in lobules and are separated by delicate fibrous septa. In this lipoma-like variant, the lesion is predominantly composed of mature white fat resembling a lipoma, with only scant brown fat differentiation or vacuolization. Vascular network: Thin capillary-rich stroma is present within septa, reflecting the vascular nature of brown fat components that may be variably represented. The overall histology lacks significant cellular atypia or lipoblasts. The sparse presence of multivacuolated cells, if present, and occasional mitochondria-rich cytoplasm may indicate residual brown fat differentiation, supporting a diagnosis within the spectrum of hibernoma rather than conventional lipoma. Clinical significance: Benign adipocytic tumor with lipoma-like histology; differentiating from liposarcoma is essential to avoid overtreatment; surgical excision is typically curative. Potential clinical use: diagnostic education, histopathology training, differential diagnosis evaluation, pathology atlases. Correlative imaging and clinical history enhance accuracy overall.

Comprehensive Description: This is a histopathology slide of a cutaneous skin biopsy examined with bright-field microscopy after hematoxylin and eosin staining. The specimen shows a perpendicular transection through epidermis, dermis, and subcutaneous fat. The epidermis exhibits marked acanthosis with elongation of rete ridges and mild hyperkeratosis, while the basal layer remains intact. The dermis contains variably dense fibrous stroma with sparse chronic inflammatory cells. Beneath the dermis, the subcutaneous tissue is dominated by mature adipocytes arranged in lobules separated by thin fibrous septa. No cytologic atypia, mitotic figures, or infiltrative tumor margins are evident. The overall architecture favors a benign adipose-rich process, such as a lipomatous lesion, with epidermal remodeling that may accompany adjacent subcutaneous fat expansion. There is no clear evidence of malignancy, inflammatory panniculitis, or granulomatous reaction in the field shown. Staining quality permits clear visualization of adipocytes (large clear cytoplasm), connective tissue septa, and epidermal layers. This image is useful for dermatopathology teaching, correlating histologic patterns of lipomatous subcutaneous lesions with overlying epidermal changes, and supporting differential diagnosis including lipoma, fibrolipoma, and, less likely, liposarcoma in cutaneous/subcutaneous tissue. It provides a reference for pattern recognition and morphology in skin biopsy evaluation. Clinically relevant across education and research.