Annulate lamellae in human tumor cells.

Annulate lamellae have been found in a primitive neuroectodermal tumor, a metastatic cerebellar tumor, a testicular seminoma, a retinoblastoma and three melanomas. These annulate lamellae are arranged in stacked parallel arrays in the cytoplasm of tumor cells. The number of annulate lamellae observed to comprise a single stack varies from 2--4 in the seminoma tumor to 5--18 in the cerebellar tumor. Although the functional significance of annulate lamallae is still unknown, in many instances they have been found to be continuous with rough-surfaced cisternae of the endoplasmic reticulum and ribosomes have been demonstrated on the surface of annulate lamellae. This may suggest that annulate lamellae participate in protein synthesis.