Dysgerminomas resemble seminomas microscopically. They are composed of monomorphic tumor cells arranged in diffuse sheets, trabeculae, cords, or nests. There may be pseudoglandular spaces due to discohesion among tumor cells. The tumor cell clusters are separated by delicate fibrous septa containing T lymphocytes. In some cases, there may be well-formed lymphoid follicles with germinal centers. About 20% of cases show granulomatous response (as shown here) consisting of granulomas formed by epithelioid histiocytes and multinucleated giant cells (not seen in this image). The polygonal tumor cells have well-defined cell membranes, clear or lightly eosinophilic cytoplasm, large vesicular nuclei, prominent nucleoli, and brisk mitotic activity. The cytoplasmic clarity is due to glycogen content. About 5% of dysgerminomas have syncytiotrophoblastic cells, usually in a perivascular location. Such cases show modest elevations in serum hCG levels. This feature does not change the prognosis. Choriocarcinoma must be excluded by thorough sampling.