Desmoplastic fibroblastoma (collagenous fibroma).

Desmoplastic fibroblastoma (DF) is a rare fibrotic tumor that has a wide anatomic distribution and it can appear in deep sections of the subcutis, in fascia, in aponeurosis or in skeletal muscles. This report describes a case of DF that appeared on the left side of the neck of a 55-year-old male as a 3.5-cm solitary, firm nodule. Histologically, it was composed of stellate or bland spindle-shaped cells embedded in a loose collagenous stroma. The entrapment of fat and muscle tissues was focally identified at the edges of the tumor. The stellate and multinucleated cells in the lesion were strongly positive for vimentin but negative for cytokeratin, smooth muscle actin, desmin, S-100, CD34, factor XIIIa, and CD68. These findings suggest that the stellate and multinucleated cells in the lesion were of fibroblastic origin and this neoplasm was pathologically benign.