CD34-positive eruptive fibromas

The list of entities comprising a proliferation of CD34 (+) spindle cells continues to grow Described, herein, is a patient who had an indolent 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 extremities. They appeared 6 years previously and had slowly increased in number. Biopsy from the neck showed a proliferation of plump spindle cells, associated with delicate collagen, in the upper reticular dermis. No atypia nor mitotic figures were present. The spindle cells were negative for S-100, muscle actins, and Factor XIIIa, but stained intensely with CD34. This unusual mesenchymal proliferation of CD34 (+) apparent dermal dendrocytes did not have the storiform pattern, short fascicles, nor mitotic figures of DFSP. The completely negative muscle markers helped to exclude dermatomyofibroma, and no morphological evidence of vasoformative differentiation was seen. The clinical picture militated against solitary fibrous tumor. These eruptive tumors are benign and thought to represent a distinctive fibroma produced by proliferated CD34 (+) stromal cells.