The sheets of tumor cells are separated by slender fibrous septa. Diffuse or focal intense lymphoid infiltrate is seen in most tumors. Glycogen may be demonstrated in the cytoplasm of the tumor cells. Sheets of tumor cells separated by thin fibrous septa heavily infiltrated by lymphocytes. High magnification showing uniform tumor cells.
Mitotic figures are usually infrequent.
In about a third of cases, noncaseating granulomatous areas containing small giant cells are found. In some seminomas, the neoplastic cells are more pleomorphic and have more mitotic figures than in typical seminoma. These tumors have been called anaplastic seminomas. Left panel shows multinucleate giant cells of foreign body type. Right panel shows syncytiotrophoblast-like tumor giant cell.