Table 2.

Recently described adipocytic tumors

	Clinical features	Morphologic features	Immunophenotype	Genetic abnormality
Anisometric cell lipoma (dysplastic lipoma)	Adults; M > F; subcutis or superficial soft tissue; often posterior neck and upper trunk	Mature adipocytes with significant variation in size and shape, accompanied by frequent microscopic foci of fat necrosis, minimal nuclear atypia, and Lochkern change	Loss of RB1 expression (complete or partial), +p53	Heterozygous RB1 deletion
Atypical spindle cell/pleomorphic lipomatous tumor	Adults; M > F; superficial or deep soft tissue; extremities (mainly distal) and limb girdles, but can involve any part of the body (including body cavities and viscera)	Various proportions of spindle cells, pleomorphic (multinucleated) cells, adipocytes, and/or lipoblasts with collagenous to myxoid stoma and infiltrative borders	+CD34 (majority), loss of RB1 (about 50%), +S-100 (variable), +desmin (variable)	Deletions/losses of 13q14 (RB1, RCBTB2, ITM2B, and DLEU1), monosomy 7