COLLAGENOUS FIBROMA (DESMOPLASTIC FIBROBLASTOMA) - A REPORT OF 7 CASES

We report the clinical features, light microscopic and ultrastructural appearance, and the immunohistochemical profile of seven benign fibro us tumors recently designated as desmoplastic fibroblastoma. The tumor s occurred in four women and three men, who ranged in age from 41 to 7 6 years (mean, 53 yr). The tumors were located in the left thigh, righ t shoulder, right upper arm, left forearm, right neck, posterior neck, and foot and measured from 1.5 to 8 cm (mean, 4.6 cm) in greatest dia meter. Four tumors were located in the subcutaneous tissue, two tumors were intramuscular, and one tumor involved the subcutaneous tissue an d adjacent skeletal muscle, Six patients underwent a simple excision; one patient underwent a wide excision of the tumor. Grossly, the tumor s were well circumscribed with a white to tan-white, bulging cut surfa ce, Microscopically, they all displayed similar features and were comp osed of widely separated stellate- or spindle-shaped cells embedded in a hypovascular fibrous or fibromyxoid stroma. No mitotic figures, cal cifications, or necrosis were identified, Five tumors were well demarc ated, and two tumors had focally infiltrating margins, Ultrastructural examination performed on two cases showed that the tumor cells had fe atures of fibroblasts and myofibroblasts. Immunohistochemical examinat ions performed on six cases showed that all of the tumors were diffuse ly positive for vimentin. One tumor showed diffuse staining for smooth muscle actin, and two tumors were focally positive for that antibody, One tumor showed diffuse staining for muscle actin, and another one w as focally positive, Two tumors demonstrated diffuse faint staining fo r S100 protein, There was no staining for desmin, keratin, or CD34, Fo llow-up information was available in four cases and ranged from 1 to 6 0 months (average, 24 mo), No tumor recurred, Although the term desmop lastic fibroblastoma has been applied to this neoplasm, we think that the name collagenous fibroma is more appropriate for these tumors.