Proliferative fasciitis. Report of a case with histopathologic and immunohistochemical studies

We present a case of proliferative fasciitis arising adjacent to an operative scar of the right lower leg of a patient with chronic lymphatic leukemia, diabetes mellitus, and multiple subcutaneous angiolipomas. A 61-year old man had a hard mass in his right lower leg that had rapidly increased in size in the past 10 days. The mass was microscopically composed of a dense proliferation of spindle cells forming interlacing fascicles admixed with an inflammatory infiltrate of lymphocytes and eosionphils, focal hemorrhage, and myxomatous change as typically seen in nodular fasciitis as well as many characteristic ganglion cell-like giant cells. Immunohistochemically, most of the spindle-shaped cells were positive for vimentin and alpha-actin, whereas the ganglion cell-like giant cells were positive for vimentin and negative for alpha-actin and lysozyme. We suggest that the main component cells of proliferative fasciitis are fibroblastic in nature, many of which are myofibroblasts in large part, whereas the ganglion cell-like giant cells are related more closely to fibroblasts rather than histiocytes or pericytes. Additionally, proliferating cell nuclear antigen (PCNA) stain revealed that many of the fibroblastic cells showed high proliferative activity, especially in the hypercellular areas, although there was no significant difference in PCNA staining between the focus traumatized by the needle biopsy and the nontraumatized areas.