Smooth muscle hyperplasia of the testicular adnexa clinically mimicking neoplasia: clinicopathologic study of sixteen cases.

Sixteen cases of a largely unrecognized benign cause for an intrascrotal mass are reported herein. These cases represent a nonneoplastic excess of native smooth muscle in the paratestis or spermatic cord growing between or around vessels or efferent ducts. The patients ranged in age from 46 to 81 years, with a mean age of 63 years. The size, available in 10 of the cases, ranged from 6 mm to 7 cm, with a mean of 2.5 cm; there was no side predilection. Microscopically, the lesions consisted of fascicles of smooth muscle, growing in a periductal, perivascular, interstitial, or mixed pattern. The cohesive, interlacing growth pattern of a leiomyoma was missing in all cases. The cause of this lesion is not apparent, although microscopic epididymal or vas deferens duct ectasia in some cases suggests a possible obstructive etiology. In any case, these are benign and without clinical significance after excision and correct diagnosis. Follow-up was available in 13 patients with no recurrences observed from 1 month to 16 years postoperatively.