A seminoma is a germ cell tumor of the testicle 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.

[5] Blood tests may detect the presence of placental alkaline phosphatase (ALP, ALKP, ALPase, Alk Phos) in fifty percent of cases.

However, Alk Phos cannot usefully stand alone as a marker for seminoma and contributes little to follow-up, due to its rise with smoking.

[9] The cut surface of the tumour is fleshy and lobulated, and varies in colour from cream to tan to pink.

[5] Microscopic examination shows that seminomas are usually composed of either a sheet-like or lobular pattern of cells with a fibrous stromal network.

The pathology of the removed testicle and spermatic cord indicate the presence of the seminoma and assist in the staging.

Active surveillance consists of periodic history and physical examinations, tumor marker analysis, and radiographic imaging.

Modern radiotherapy techniques as well as one or two cycles of single-agent carboplatin have been shown to reduce the risk of relapse, but carry the potential of causing delayed side effects.