Posttraumatic spindle cell nodules. Immunohistochemical and ultrastructural study of two scrotal lesions

We studied two cases of proliferative spindle cell lesions that developed in the scrotum secondary to trauma. The two patients, 22 and 67 years of age, presented clinically with tumor masses and were treated with surgical excision. No recurrences were seen after 12 and 13 months, respectively, of follow-up. In both cases the tumor nodules were associated with hematomas of the scrotal subcutaneous tissue, with disruption of the tunica dartos. The lesions were composed of monomorphic, dense, spindle cell proliferations that formed irregular nodules in the wall of the hematoma and disrupted the smooth-muscle bundles of the area. On immunohistochemical and ultrastructural studies, the tumor cells were consistent with myofibroblasts with pronounced smooth-muscle differentiation. Both cases had a striking histologic resemblance to the postoperative spindle cell nodules that occur in the genitourinary tract secondarily to surgical trauma. The morphological features, proliferating cell type, and benign clinical course are identical in both of these conditions, which appear to represent a stereotyped form of reactive change after injury and hemorrhage in the vicinity of smooth muscle.