Cutaneous mixed tumor with lipomatous stroma.

Area of Science:

• Dermatopathology
• Surgical Pathology
• Tumor Biology

Background:

• Mixed tumors typically feature epithelial and mesenchymal components, with the latter usually myxoid or myxochondroid.
• Massively lipomatous stroma is an exceptionally rare finding in cutaneous mixed tumors, with only two prior cases reported.
• Understanding the diverse stromal differentiation in mixed tumors is crucial for accurate diagnosis and classification.

Observation:

• A unique case of a 61-year-old male presenting with a 4.5-cm mixed tumor on the hand was analyzed.
• The tumor predominantly consisted of adipose tissue (over 90%), mimicking a lipoma macroscopically.
• Histological examination revealed epithelial cell nests within a lipomatous stroma, alongside scant fibromyxoid tissue.

Findings:

• Immunohistochemical analysis demonstrated features consistent with classic mixed tumors, despite the unusual stromal composition.
• The epithelial component showed nests and ribbons, with some tubular structures, embedded in abundant adipose tissue.
• This case represents a significant example of extensive lipomatous differentiation within a cutaneous mixed tumor.

Implications:

• This report contributes to the understanding of rare adipose differentiation patterns in skin mixed tumors.
• It underscores the importance of considering unusual stromal components in the differential diagnosis of lipomatous lesions.
• Further research into the mechanisms driving massive adipogenesis in mixed tumors may offer new insights into tumor development.