Classic clinical features:
(1) male 45 to 65 years of age
(2) subcutaneous mass on the back, shoulder or posterior neck
(3) solitary, circumscribed and slowly growing
(4) absence of metastasis
Histologic features:
(1) varying admixture of spindle cells and pleomorphic lipocytes
(2) may show atypical mitotic figures
(3) absence of pleomorphic lipoblasts
(4) giant cells with floret-like arrangement of multiple nuclei are common
(5) presence of ropey collagen bundles (not seen in atypical lipomatous tumors)
(6) mast cells are common
Other features:
(1) The cells are CD34 positive but negative for actin and desmin.
(2) Cytogenetics shows a loss of 13q or 16q.
(3) Absence of FISH staining for MDM2.
The tumors tend not to recur even if incompletely excised.
