Spindle Cell Lipomas in Women: A Report of 53 Cases.

Spindle cell lipomas (SCL) are typically tumors of the upper back/neck (shawl region) of men (80% to 90%). In general, there is a frequent tendency to restrict the diagnosis to this specific clinical scenario and a hesitancy to diagnose SCL in women. We hypothesized that SCL in women have a more varied presentation. A total of 395 SCL were diagnosed at our institution over the last 11 years. The diagnosis of SCL in women was confirmed by re-review. Immunohistochemical stains for CD34, desmin, estrogen receptor, and p16 were performed. In a subset, fluorescence in situ hybridization to detect Retinoblastoma1 (RB1) gene deletion was performed. Of 395 SCLs, 331 (86%) occurred in men; 53 (14%) occurred in women (11 cases excluded). Of the 64 SCL in women, 58 had available material. In total, 53 of 58 were confirmed as SCL. Women were younger at diagnosis (median, 51 y; range, 5 to 76 y) compared with men (64 y; range, 23 to 98 y), P<0.0001, t test. SCL in women typically occurred outside the shawl distribution (36/53, 68%) compared with men (95/331, 29%) (P<0.001), including extremities (16/53, 30% vs. 32/331, 10%) and face (11/53, 21% vs. 47/331, 14%). Dermal SCL in women were also relatively common (16/53, 30%). The cases demonstrated varying proportions of bland spindled cells, ropey collagen, myxoid matrix, and adipocytes. By immunohistochemistry, 46/46 were CD34, 48 of 48 were desmin negative, 33 of 42 were estrogen receptor negative, and 29 of 42 had loss of p16 expression. In total, 12 of 14 showed RB1 loss by fluorescence in situ hybridization. SCL in women frequently occurs in unconventional locations and in at a slightly younger patient age.