Rare variants of the classic seminoma include anaplastic seminoma (5 to 10%) and spermatocytic seminoma (4 to 6%).
Anaplastic Seminomas : Anaplastic seminomas are distinguished from classic seminomas by greater nuclear atypia and a higher mitotic rate.
Spermatocytic Seminomas : Spermatocytic seminomas are uncommon tumours occurring in patients older than those with classic seminoma (more than 50 years old). These are indolent growths, with virtually no tendency to metastasize. The lesions tend to be larger than those of classic seminoma. These lesions are composed of mixed population of cells, including smaller (6 to 8 micro-meter) cells resembling secondary spermatocytes, (hence the spermatocytic designation), medium-sized (15 to 18 micro-meter) cells, and scattered giant cells.
Abstract: Spermatocytic seminoma. Hum Pathol.1994 Oct;25(10):1035-42.
Spermatocytic seminoma is a rare testicular neoplasm that occurs only in adults (range, 25 to 87 years; mean, 54). It has no ovarian homologue and is found only in descended testes. It is not associated with other types of germ cell neoplasia. Orchiectomy is curative in virtually all cases; of more than 200 known cases, only one has metastasized. In a dozen cases sarcomas have arisen in the testes in association with spermatocytic seminoma; most of these patients have died of metastatic sarcoma after short intervals. The gross appearance is characteristically edematous or gelatinous and more than half the tumors have been more than 5 cm in diameter. Microscopically, they are composed of sheets of small, medium, and large cells with spherical nuclei. The chromatin is dense in the small cells and filamentous in the medium and large ones. The cytoplasm is eosinophilic to amphophilic and lacks glycogen. It is not associated with intratubular germ cell neoplasia of the undifferentiated type. Analyses of DNA content have failed to show haploid populations and the lectin binding does not show maturation toward spermatocytes. Differing from seminoma in essentially all characteristics, it is not a variant of seminoma.
Abstract: Anaplastic variant of spermatocytic seminoma. Hum Pathol. 1996 Jul;27(7):650-5.
Four examples of spermatocytic seminoma with a predominant anaplastic component occurred in men 33 to 43 years of age, without histories of cyptorchidism. The seminomas presented with painless testicular masses recognized 3 to 18 months before orchiectomy. Preoperative serum measurements of human chorionic gonadotropin and alpha-fetoprotein were negative. All tumors contained areas (10% to 30% of the tumor) in which the three cell types characteristic of conventional spermatocytic seminoma could be identified under light microscopy. The predominant anaplastic component also contained the three cell types, but the nuclei had prominent nucleoli with granular and filamentous chromatin. In addition, sheets of cells with vesicular nuclei and prominent nucleoli superficially resembling embryonal carcinoma were found. There were numerous large mononuclear and multinucleated giant cells with bizarre nuclei and prominent nucleoli, but no sarcomatous elements. Many normal and abnormal mitotic figures were present. Tunical and vascular invasion and extensive necrosis were constant features. Immunohistochemistry documented p53 protein overexpression in two tumors, but neoplastic cells were negative with immunostains for placenta-like alkaline phosphatase, leukocyte common antigen, neuron-specific enolase, alpha-fetoprotein, human chorionic gonadotropin, vimentin, and cytokeratins. Ultrastructural examination of the anaplastic component showed large rope-like nucleoli, but the cytoplasmic features were similar to those of conventional spermatocytic seminoma. Despite the presence of a major anaplastic component, no patient has developed metastasis. Larger series and longer follow-up are needed to understand the natural history of these neoplasms.