Mesothelioma of tunica vaginalis testis in a child

Mesothelioma of the tunica vaginalis testis is uncommon in adults and exceedingly rare in children. This tumor not only raises clinical and histological diagnostic problems, but also has an unpredictable clinical course, particularly in the pediatric age group. We report on a boy with mesothelioma of the tunica vaginalis, and discuss clinical and pathological findings. CASE REPORT A 6-year-old boy who had previously undergone right inguinal herniotomy at age 2 years 6 months presented with a right hydrocele. Surgical exploration through an inguinal incision revealed 45 ml. of bloodstained fluid in the hydrocele sac. The visceral and parietal surfaces of the tunica vaginalis were thickened, and covered with multiple yellowish plaques and nodules ranging from 15 to less than 0.1 mm. (fig. 1). Frozen section examination suggested a yolk sac tumor and inguinal orchiectomy was performed. Pathological evaluation revealed multiple papillary and solid tumors arising from the tunica vaginalis (fig. 2, A). These masses showed focal invasion of the tunica albuginea but they did not penetrate the testis or epididymis. Lymphvascular involvement was present at the resection margin of the spermatic cord and the solid areas had rudimentary tubules. Multiple psammoma bodies were identified as well as occasional mitotic figures (fig. 2, B). Immunocytochemistry studies demonstrated a positive staining reaction for cytokeratins, CAM 5.2, AE 1IAE 3 and epithelial membrane antigen in the tumor cells. Immunoreactivity was negative for carcinoembryonic antigen Ber-Ep4 (a specific epithelial marker) and a-fetoprotein. Electron microscopy revealed irregular microvilli of variable length on the free surfaces of the tumor cells and within spaces between the cells, consistent with a mesothelial cell origin. Tumor cells were also identified in the bloody hydrocele fluid. The diagnosis was low grade mesothelioma. Followup at 24 months showed no evidence of recurrent disease.