MONOCLONAL ANTIBODY CONFIRMATION OF A PRIMARY LEIOMYOMA OF THE TESTIS

Abstract

Primary mesenchymal tumors of the testis are rare, with fewer than 30 cases reported in the world literature. Although the data are scant, primary mesenchymal testis tumors appear to exhibit the same clinical characteristics as their counterparts in other tissues and organs.' Leiomyoma has been reported throughout the genitourinary tract, yet it is extremely rare in the testis, with only 6 cases reported. Previous authors have based their diagnosis on nonspecific histological stains or gross histological analy~is.~,~ We report diagnostic confirmation of a testis leiomyoma using novel monoclonal antibodies. CASE RE PORT An 18-year-old man presented with a 3-year history of a painless right testicular mass. He denied any constitutional symptoms, weight loss, lower urinary tract symptoms or gynecomastia. Physical examination was remarkable for a 1 cm. indurated mass located over the upper pole of the right testis. Serum lactic dehydrogenase, a-fetoprotein and p-human chorionic gonadotropin were within normal limits. The chest x-ray was normal. Scrota1 ultrasound revealed a 1 cm. hypoechoic mass in the superomedial aspect of the right testis (fig. 1). Inguinal exploration with wedge resection of the mass was performed. A frozen section of the mass was interpreted as a spindle cell neoplasm of uncertain malignant potential and radical orchiectomy was completed. Followup was uneventful 1 year after surgery. DISCUSSION Previously, the diagnosis of a primary testis leiomyoma was based on nonspecific histological stain^,^,^ which leads to uncertainty with regard to neoplasm identity, especially in view of its rarity. In our case actin specific monoclonal antibodies were used to detect smooth muscle specific actin in the neoplastic cells (fig. 2). Previous study has proved that the monoclonal antibodies used in our case (clone 14A and HHF 35) reliably mark the product of the a and y isoactin genes, thus detecting neoplastic cells of smooth muscle origin.4 The morphological appearance of the tumor did not reveal mitotic figures, hemorrhage or necrosis, thus supporting the diagnosis of a clinically benign leiomyoma. The patient is diseasefree at 1 year postoperatively. Myoid cells, or potentially their progenitors, may give rise to these particular tumors in the testis. Myoid cells can be found in the tunica albuginea, tunica propria of the seminiferous tubules and smooth muscle of blood vessel walls. Testis leiomyomas most likely originate from the progenitors of smooth muscle cells and not the actual smooth muscle cells themselves. These progenitor cells remain to be identified.