Spindle cell lipoma.

A clinical, light- and electronmicroscopic study of 14 patients with spindle cell lipoma is presented. Spindle cell lipoma is considered to be a distinctive lipomatous tumour histologically characterized by a mixture of fat cells and fibroblast-like spindle cells, ultrastructurally similar to fibroblasts, in a matrix with varying amounts of collagen and mucosubstances. The tumours showed a predominance for elderly men and all but one were situated in the posterior neck, shoulder region or upper back. The tumours varied between 1 and 9 cm, with a median value of 5 cm, in the widest diameter and were entirely or almost entirely situated in the subcutaneous tissue. A follow-up study of 11 patients, observed for 1-25 years, confirmed that the clinical course is benign. The differential diagnosis is discussed and it is emphasized that spindle cell lipoma is easily misinterpreted as sarcoma. Three tumours showed a pronounced nuclear polymorphism without mitotic activity, thought to be regressive in nature. The cellular change in these three tumours are presumed to be analogous with those in so called ancient neurilemmoma and therefore the name ancient spindle cell lipoma is proposed for the polymorphic spindle cell lipomas.