Nodular sclerotic change in dermatofibrosarcoma protuberans: a potential diagnostic problem.

Nodular sclerotic change in dermatofibrosarcoma protuberans (DFSP) is not a well-recognized event. Sclerotic change is reported in three patients with DFSP: a 33-year-old woman with a left subclavian mass, a 29-year-old woman with a mass on the left crus and a 31-year-old man with a mass on the left cheek. Histologically, lesions consisted of two types of feature, one type being typical of DFSP and the other being rich in collagen. In the first patient, each type formed a distinct compartment, each of which contained scattered cells containing melanin pigment. In the second patient, foci with typical DFSP histology were distributed within the collagen-rich area and also formed a substantial compartment in the periphery of the lesion, with pigmented cells being distributed mainly in and around the cellular area. In the third patient, the collagenous area occupied about half of the lesion. There was no pigmentation. In all three cases the collagen-rich area contained sparsely distributed fibroblast-like cells that stained positive with CD34. Sclerotic change in DFSP could cause substantial difficulty in diagnosis if the biopsy material were partial and small. The clinical history and knowledge about the existence of this kind of histological variation in DFSP are important.