FINAL DIAGNOSIS: JUVENILE GRANULOSA CELL TUMOR
Juvenile granulosa cell tumor (JGCT) of the testis is an extremely rare entity. Only 11 cases of JGCT of the testis have been reported to the national tumor registry as of December 2001.
JGCT of the testis is similar in appearance to its ovarian counterpart but occurs in a more restricted age range, with almost all patients under 5 months of age. There are no well-established risk factors, although a disproportionate number occur in patients with either gonadal dysgenesis or anomalies of sex chromosomes, including patients with X/XY mosaicism.
A testicular mass is invariably the presenting feature. Grossly, it consists of a solid to cystic, gray to yellow nodule. The cystic foci are filled with mucoid to watery fluid. Microscopically, there are round, follicle-like structures filled with watery-appearing, often mucicarminophilic, fluid. The intervening solid areas consist of nodules and sheets of cells, with frequently conspicuous stromal hyalinization. The cells have an abundant amount of pale to eosinophilic cytoplasm and hyperchromatic, round nuclei with nucleoli. Mitotic figures may be numerous. Immunohistochemical study shows positivity for inhibin, vimentin, CD99, and occasionally for cytokeratin, smooth muscle actin, and desmin. Despite worrisome histologic features, this tumor behaves in a benign fashion.
Pathological confirmation of JGCT of the testis relies on the microscopic identification of morphological features that may be difficult to distinguish from those of yolk sac tumor. Both yolk sac tumors and JGCTs contain mucin-containing follicles that may be intermixed with solid components. In addition, the rarity of its presentation may intensify the difficulty in definitively diagnosing JGCT in the testis. While the lack of classic yolk sac tumor structures, such as Schiller-Duvall bodies and negative immunoreactivity to AFP, may support the diagnosis of JGCT in some microscopically ambiguous cases, positive immunoreactivity to inhibin provides excellent additional diagnostic usefulness.
Contributed by Lei Chen, MD, PhD