Spermatocytic seminoma (or, alternatively, spermatocytic tumor) of the testis is rare and errors in pathologic diagnosis are still made. As it has a good prognosis, except when it, rarely, undergoes sarcomatous transformation, accurate diagnosis and differentiating it from usual seminoma and other malignant neoplasms such as lymphoma are crucial. To potentially contribute information of diagnostic aid we reviewed the largest series of cases reported to date to characterize in detail their histologic spectrum. The patients ranged from 30 to 81 years (average, 52 y); 30% were in the fourth decade. The neoplasms ranged from 1.4 to 15 cm (average, 5.7 cm). Most were fleshy, soft, and often lobulated and 11 were edematous or mucoid. Low-power microscopic examination either showed a predominant multinodular (43/85) or diffuse (42/85) pattern. All tumors had the classic “tripartite” cellular population. Five tumors showed a relatively monomorphic population of the intermediate cell type with vesicular chromatin and very prominent nucleoli, at least focally. Two tumors underwent sarcomatous transformation, with 1 having a focus of atypical cartilage. Additional findings, some not previously reported or emphasized, included: (1) frequent edema fluid (87%) often causing spaces, both follicle-like (24%) and irregular (39%), a finding seen in some usual seminomas (but less frequently) and rarely seen in lymphomas; (2) tumor nodules showing partial rims of fibrin (20%); (3) a distinctive arrangement of connecting tumor islands (19%); (4) prominent lymphocytic infiltrates (8%); (5) granulomatous inflammation (1%); (6) striking mitotic activity and apoptosis; (7) intratubular spread (64%); and (8) vessel invasion (11%) and necrosis (8%). Awareness of these aspects may be of importance either at the time of intraoperative evaluation or on final pathologic analysis and help avoid significant errors in diagnosis.