|Classification and external resources|
|ICD-10||C62 (ILDS C62.920)|
Seminoma (also known as pure seminoma or classical seminoma) is a germ cell tumor of the testis or, more rarely, the mediastinum or other extra-gonadal locations. It is a malignant neoplasm and is one of the most treatable and curable cancers, with a survival rate above 95% if discovered in early stages.
Testicular seminoma originates in the germinal epithelium of the seminiferous tubules. About half of germ cell tumors of the testis are seminomas. Treatment usually requires removal of one testis, but this does not affect fertility or other sexual functioning.
The average age of diagnosis is 40 years. This is about 5 to 10 years older than men with other germ cell tumors of the testes. In most cases, they produce masses that are readily felt on testicular self-examination; however, in up to 11 percent of cases, there may be no mass able to be felt, or there may be testicular atrophy. Testicular pain is reported in up to one fifth of cases. Low back pain may occur after metastasis to the retroperitoneum.
Some cases of seminoma can present as a primary tumour outside the testis, most commonly in the mediastinum. In the ovary, the tumor is called a dysgerminoma, and in non-gonadal sites, particularly the central nervous system, it is called a germinoma.
Blood tests may detect the presence of placental alkaline phosphatase (PLAP) in fifty percent of cases. However, PLAP cannot usefully stand alone as a marker for seminoma and contributes little to follow-up, due to its rise with smoking. Human chorionic gonadotropin (hCG) may be elevated in some cases, but this correlates more to the presence of trophoblast cells within the tumour than to the stage of the tumour. Serum alpha fetoprotein is not elevated in classical seminoma.
The cut surface of the tumour is fleshy and lobulated, and varies in colour from cream to tan to pink. The tumour tends to bulge from the cut surface, and small areas of hemorrhage may be seen. These areas of hemorrhage usually correspond to trophoblastic cell clusters within the tumour.
Microscopic examination shows that seminomas are usually composed of either a sheet-like or lobular pattern of cells with a fibrous stromal network. The fibrous septa almost always contain focal lymphocyte inclusions, and granulomas are sometimes seen. The tumour cells themselves typically have abundant clear to pale pink cytoplasm containing abundant glycogen, which is demonstrable with a periodic acid-Schiff (PAS) stain. The nuclei are prominent and usually contain one or two large nucleoli, and have prominent nuclear membranes. Foci of syncytiotrophoblastic cells may be present in varied amounts. The adjacent testicular tissue commonly shows intratubular germ cell neoplasia, and may also show variable spermatocytic maturation arrest.
In recent years, these tumors have been shown to have dramatic sensitivity to both radiotherapy and cytotoxic chemotherapy. The management of childhood seminoma is similar to that of adult seminoma. Inguinal orchiectomy is required in almost all cases.
5-year survival rate is approximately 90% as of 2008.
A study of 31 men with metastatic germ cell tumor of the testis and delayed orchidectomy found that in men with pure seminoma, chemotherapy alone was sufficient to eliminate the cancer from the testis. The authors of this study suggest that treatment of pure seminoma may not require orchidectomy. Event-free survival of this group of men at an average followup of 4 years was 81.8%.
Relation to spermatocytic seminoma 
Additional images 
Orchidectomy specimen showing seminoma
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