Ultrastructure of developing and malignant germ cells.
Ultrastructural studies have provided special insights on the growth and differentiation of normal and neoplastic germ cells. Prespermatogenic germ cells in the fetal and postnatal testis are large spherical to ovoid cells characterized by a central symmetrical nucleus, prominent reticular nucleoli and abundant cytoplasm with accumulation of glycogen and paucity of other organelles. Similar findings have been observed in seminoma and intratubular neoplasia. These observations support origin of the tumours from germ cells at early stages of differentiation. Evidence is presented to suggest that the pathogenesis of germ cell neoplasia involves excessive proliferation of precursor germ cells associated with loss of intercellular communication.