Figure 1. Stromal p16 expression (A to G) and tumor cells (H) of ovarian adult granulosa cell tumors. An adult granulosa cell tumor is characterized by small, bland-appearing, cuboidal to polygonal tumor cells arranged in anastomosing trabeculae, nests, and cords (A). The diagnosis of adult granulosa cell tumor was confirmed by positive immunostaining for inhibin-α (B), calretinin (C), and CD56 (D). In benign sex cord-stromal tumors, only some stromal cells displayed weakly nuclear or cytoplasmic p16 immunoreactivity (E). Low-power magnification of adult granulosa cell tumors showing uniform and strong stromal p16 immunoreactivity. The tumor cells did not exhibit p16 expression (F). At medium-power magnification, p16 expression was observed in both the nucleus and cytoplasm of the spindle-shaped stromal cells (G). In a few cases of adult granulosa cell tumors, p16 protein was localized within the tumor cells, most of which exhibited weak cytoplasmic immunoreactivity (H). Original magnifications: F, ×40; A, B, D, E, and G, ×100; C and H, ×200.