Histogenesis of granular cell tumour--an immunohistochemical and ultrastructural study.

Fifteen cases of granular cell tumour of superficial soft tissues or tongue were immunohistochemically evaluated for different types of intermediate filament proteins and for laminin, a glycoprotein of basal laminae. Four of the tumours were studied ultrastructurally. The tumour cells appeared to contain only vimentin-type of intermediate filament protein. The lobules of tumour cells were surrounded by laminin-positive material, but in contrast to schwannomas and neurofibromas, the individual tumour cells were not covered by laminin. In line with the immunohistochemical observations, by electron microscopy basal lamina-like material could not be demonstrated between individual cells, but only surrounding groups of cells. Lysozyme, a histiocytic marker, was absent in the tumour cells. Our results do not confirm any particular cell type for the histogenetic origin of granular cell tumour, but suggest that it may rather be derived from uncommitted possibly nerve-related mesenchymal cells.