Image 5 of 36



Image Description

Microscopic Features: The typical spindle cell lipomas in subcutaneous locations are well-circumscribed (as seen in the gross specimen photos) and usually encapsulated. Tumors in the dermis or intramuscular locations are ill-defined and appear infiltrative. They have a range of morphologic appearances depending upon the relative proportion of mature adipose tissue, bland spindle cells, and fibromyxoid stroma with thick collagen bundles.

Some tumors are lipoma-like with abundant mature adipose tissue and only scattered foci of spindle cells or pleomorphic cells (left panel). Others are composed predominantly or exclusively of spindle/pleomorphic cells with only rare or no mature adipocytes. These fat-free lipomas (right panel) may show pure spindle cell pattern, pure pleomorphic pattern, or an admixture of the two.

Image 5 of 36