Desmoplastic fibroblastoma (collagenous fibroma).

Desmoplastic fibroblastoma is a vary rare subcutaneous proliferation. We describe a case of desmoplastic fibroblastoma in a 24-year-old Korean woman who presented with a 2.5 cm solitary and firm nodule on her back which had been present for 3 months. Histologic studies showed a well demarcated subcutaneous tumor composed of stellate or spindle shaped cells embedded in hypovascular fibrous or fibromyxoid stroma. No mitotic figures, calcification, or necrosis were observed. The stellate or spindle shaped cells were positive for vimentin. The stroma stained positively with Alcian blue and Masson trichrome. S-100 protein, actin, desmin, and elastic fiber stains were all negative in the stellate or spindle shaped cells. There has been no recurrence or metastasis of the tumor over an 18-month follow-up.