What accounts for the majority of testicular cancers?

The majority of testicular cancers are indeed classified as germ cell tumors. Germ cell tumors originate from the germ cells, which are the cells responsible for producing sperm in males. These tumors account for approximately 95% of all testicular cancer cases. Within this category, there are different subtypes, including seminomas and non-seminomatous germ cell tumors, which further classify the type of germ cell tumor based on their characteristics and behavior.

Seminomas, while a common and significant subtype of germ cell tumors, represent only a portion of the overall germ cell tumor diagnosis. They are distinguished by their tendency to grow more slowly and have a better prognosis compared to some of the non-seminomatous types. Non-germ cell tumors are quite rare in the context of testicular cancer, and leukemia is unrelated as it is a cancer of the blood and bone marrow rather than the testicular tissue.

This emphasis on germ cell tumors reflects the prevalent understanding of testicular cancer's epidemiology and guides the diagnostic and treatment approaches that oncologists use when dealing with this form of cancer.