Myofibroblastic pseudotumor mimicking epididymal sarcoma. A clinicopathologic study of three cases.

The clinical and pathologic features of three cases of epididymal pseudotumor are described with emphasis on its differential diagnosis and histopathogenesis. The first lesion was found histologically worrisome in the region of ductus epididymis by a torsioned testis in an 8-month-old boy, although the lesion was clinically indistinctive, and grossly not remarked. Histodiagnostic difficulties are encountered because this lesion forms numerous infiltrative spindle cells in haphazard arrangement. Ultrastructurally, the cell components of this lesion are predominantly myofibroblasts, intermediate cells between fibroblasts and myocytes. Similar epididymal lesions with the same cell components were identified in the two other infantile cases on the review of 36 consecutive orchiectomy specimens all obtained for testicular torsion. These three boys were found to present with a relatively gradual clinical course of the testicular torsion. It is suggested that myofibroblastic proliferation in the epididymal location histologically reminiscent of sarcomas occurs under ischemic circumstances.