CD34-POSITIVE ERUPTIVE FIBROMAS

The list of entities comprising a proliferation of CD34 (+) spindle ce lls continues to grow Described, herein, is a patient who had an indol ent eruption of scattered papules composed of CD34 (+) spindle cells, beginning in adolescence. An 18-year-old female patient presented with asymptomatic, tan/brown papules over the neck, chest, and proximal ex tremities. They appeared 6 years previously and had slowly increased i n number. Biopsy from the neck showed a proliferation of plump spindle cells, associated with delicate collagen, in the upper reticular derm is. No atypia nor mitotic figures were present. The spindle cells were negative for S-100, muscle actins, and Factor XIIIa, but stained inte nsely with CD34. This unusual mesenchymal proliferation of CD34 (+) ap parent dermal dendrocytes did not have the storiform pattern, short fa scicles, nor mitotic figures of DFSP. The completely negative muscle m arkers helped to exclude dermatomyofibroma, and no morphological evide nce of vasoformative differentiation was seen. The clinical picture mi litated against solitary fibrous tumor. These eruptive tumors are beni gn and thought to represent a distinctive fibroma produced by prolifer ated CD34 (+) stromal cells.