Classification of the testicular cancer depends on their cells of origin in the testis.

The testis is made up of supporting cells or stroma that secrete the male hormone called testosterone (from Leydig cells) and 250 to 300 seminferous tubules. The tubules are again made up of supporting or sertoli cells and germ cells or spermatogonia (sperms come from these cells).

I) 95% of all testicular tumors originate from the germ cell and are hence called the germ cell tumours. These tumors have the following subtypes-

      a) Seminoma is a type of germ cell tumor that stems from the germinal epithelium of the seminiferous tubules with a possibility to metastasize. It accounts for 40% of the testicular tumors.

       - Spermatocytic seminoma is a subtype of seminoma. It is an indolent tumor that hardly metastasize.

    b) Non Seminomatous germ cell tumor comprises of a combination of any of following subtypes.

       - Embryonal carcinoma: Rapid growth and pain is a common feature of this malignancy and it accounts for 20 to 25% of the tumors

       - Teratoma: Theycan be huge tumors made up of more than a single cell type. Teratoma of the testicle are the least aggressive form of cancer with a potential to relapse, It accounts for 25 to 35% of the testuclar tumors

       - Choriocarcinoma: Relatively rare (1% of testicular tumors) but most aggressive of the germ cell tumors. It spreads to the brain, lungs and the liver quite early during the disease. Bleeding is common in patients with choriocarcinoma. Yolk sac tumors appear as large primary tumor

II) Testicular Non-germ cell tumors account for 5 to 10% of the testicluar tumors and depending on their cell of origin there are a number of them that can manifest including the ones that orginate from the Sertoli-Leydig cells. The various types are listed for reference -

          1. Specialized gonadal stromal tumor

                 (a) Leydig cell tumor

                 (b) Other gonadal stromal tumor

          2. Gonadoblastoma

          3. Miscellaneous Neoplasms

                 (a)  Adenocarcinoma of the rete testis

                 (b)  Mesenchymal neoplasms

                 (c)  Carcinoid

                 (d)  Adrenal rest “tumor”

The testis may also rarely be the site of a metastatic tumor from another organ. Or it could be the site of a lymphoma especially in a male above 60 years. 

Other structures that surround the testis, like its membranes and epididymis, can also, although rarely, produce benign or malignat tumours. These are called paratesticluar tumors and an example is Cysadenona of Epididymis or a mesothelioma.

The incidence of testicular cancer in the USA is reported as 3.7 per 100,000 men whereas in Bombay it is 1.2 per 100,000. While testicular tumour account for 1% of all malignant tumors. Among all the patients with testicular tumors 2 to 3% are bilateral.