Germinoma

A germinoma is a type of germ-cell tumor, which is not differentiated upon examination. It may be benign or malignant. A germinoma is a type of germ-cell tumor, which is not differentiated upon examination. It may be benign or malignant. Germinomas are thought to originate from an error of development, when certain primordial germ cells fail to migrate properly. Germinomas lack histologic differentiation, whereas nongerminomatous germ-cell tumors display a variety of differentiation. Like other germ-cell tumors, germinomas can undergo malignant transformation. The tumor is uniform in appearance, consisting of large, round cells with vesicular nuclei and clear or finely granular cytoplasm that is eosinophilic. On gross examination, the external surface is smooth and bosselated (knobby), and the interior is soft, fleshy, and either cream-coloured, gray, pink, or tan. Microscopic examination typically reveals uniform cells that resemble primordial germ cells. Typically, the stroma contains lymphocytes, and about 20% of patients have sarcoid-like granulomas. Metastasis has been noted in about 22% of cases at time of diagnosis. Males are roughly twice as commonly affected in developing germinomas. They are most commonly diagnosed between the ages of 10 and 21. Often, serum and spinal fluid tumor markers of alpha-fetoprotein (AFP) and beta-HCG are tested. Pure germinomas are not associated with these markers. Nongerminomatous germ-cell tumors may be associated with increased markers such as AFP with yolk sac tumors, as well as embryonic cell carcinomas and immature teratomas and beta-HCG, which occur in choriocarcinomas. In one to 15% of germinonas, a low level of beta-HCG may be produced. Although controversial, HCG-secreting germinomas may be more aggressive than nonsecreting ones. The term 'germinoma' most often refers to a tumor in the brain that has a histology identical to two other tumors, dysgerminoma in the ovary and seminoma in the testis. Since 1994, MeSH has defined germinoma as 'a malignant neoplasm of the germinal tissue of the gonads, mediastinum, or pineal region' and within its scope included both dysgerminoma and seminoma. Collectively, these are the seminomatous or germinomatous tumors. Dysgerminoma is the most common type of malignant germ-cell ovarian cancer. Dysgerminoma usually occurs in adolescence and early adult life; about 5% occur in prepubertal children. Dysgerminoma is extremely rare after age 50. It occurs in both ovaries in 10% of patients and, in a further 10%, a microscopic tumor is in the other ovary. Seminoma is the second-most common testicular cancer; the most common is mixed, which may contain seminoma.