Immunohistochemical and ultrastructural investigation of apoptotic cell death in granular cell ameloblastoma

Apoptotic cell death in granular cell ameloblastomas was examined by immuno histochemistry using anti-single-stranded DNA (ssDNA) antibody and transmis sion electron microscopy. Routinely prepared sections of granular cell amel oblastomas showed various quantities of granular cells with some apoptotic nuclear fragments. Immunoreactivity for ssDNA was higher in granular cells than in other neoplastic cells. Ultrastructural examination revealed abunda nt lysosomes in the cytoplasm of granular cells, Numerous apoptotic cell fr agments with condensed nuclei in granular cell clusters were phagocytosed b y adjacent granular cells. On immunohistochemical characterization of cellu lar differentiation, granular cells were positive for cytokeratin, CD68, ly sozyme and alpha-1-antichymotrypsin, but negative for vimentin, desmin, S-1 00 protein, neuron-specific enolase and CD15, indicating epithelial origin and lysosomal aggregation. These features suggest that the cytoplasmic gran ularity in granular cell ameloblastomas might be caused by increased apopto tic cell death of neoplastic cells and associated phagocytosis by neighbori ng neoplastic cells.