On the histology of human seminoma: development of the solid tumor from intratubular seminoma cells.

Intratubular seminomas of the testis associated with solid tumors were studied by light and electron microscopy in order to obtain information about the earliest stage of emigration from the tubules and invasion of the interstitial space. Careful examination of numerous sections reveals that at this stage neoplastic cells protrude into evaginations of the tubule covered by basement membrance or directly invade that membrane. At the site of tumor cell emigration, the basement membrane is thickened and multilayered. Tumor cells devoid of basement membrane were found in the interstitium. Their transmigration through the basement membrane was never observed. Subsequent to the migration of seminoma cells the tubules are smaller in diameter and contain only Sertoli cells. From the observations described it is inferred that tumor cells in the interstitial tissue increase in number, form strands and lobules, and finally build up the solid tumor.