Selected Case From the Arkadi M. Rywlin International Pathology Slide Seminar Sclerotic (Fibroma-like) Lipoma, Dorsum of Right Hand

Approximately 26 sclerotic lipomas have been reported since Zelger and colleagues' 1997 report of 5 cases involving the scalp and hands. In 2006, Laskin and colleagues published 21 sclerotic lipomas in a study restricted to tumors of the hands and feet. Patients' ages ranged from 7 to 72 years (mean and median 39 y); there were 12 males and 9 females; the masses, which were mostly asymptomatic and solitary, ranged from 0.6 to 2.2 cm (median 1.2 cm, mean 1.3 cm) and involved fingers (N = 17), hands or wrists (N = 3), and toes (N = 1). Microscopically, lesions were well circumscribed, of low cellularity, and consisted of cytologically bland spindle and stellate-shaped cells with a minor component of randomly dispersed adipocytes embedded in a collagenous to myxocollagenous stroma. Eight tumors were fibroma-like with dense fibrosclerotic stroma and inconspicuous blood vessels. One tumor exhibited features of spindle cell/pleomorphic lipoma, whereas another displayed a vague onion skin-like arrangement of collagen reminiscent of a sclerotic (storiform) fibroma. The mitotic activity was negligible. Nonlipogenic cells were immunoreactive for CD99 (6/6) CD34 (6/8), S100 (4/7), and smooth muscle actin (2/6). Follow-up on 8 patients (range, 1 to 20 y, median 9.5 y) revealed no recurrence in 6 and possible persistent tumor in 2 after simple excision. The slide circulated to club members was from a 35-mm tumor on the dorsum of the right hand of a male aged 75. Club members generally agreed with a diagnosis of sclerotic lipoma but opinions differed as to whether it is a specific entity or a variant of spindle cell lipoma or dendritic fibromyxolipoma.