Specific ultrastructural markers of human pinealomas. A study of four cases.

An ultrastructural study of four pinealomas was carried out to precise eventual specific markers. Dark and clear cells joined with zonulae adherents, extensive and pleiomorphous processes, a complex vacuolar system, and characteristic organelles (lysosome-like structures, clear and dense-core vesicles, vesicle-crowned rodlets and related structures, microtubular sheaves and centriolar derivatives, membranous whorls, fibrous bodies, microtubules, heterogeneous cytoplasmic inclusions) offered a typical pattern. No correlation could be made between the histological and ultrastructural features. The authors stress the ultrastructural similarities between the human tumor cells and the mammalian pineal cells. Pinealomas appeared as a morphological entity distinct from neuronal and astrocytic tumors.