Granular cell tumor: an immunohistochemical study.

Aims and Background: Granular cell tumor, usually a benign neoplasm, has been the object of many studies because of its uncertain histogenesis and based on many immunohistochemical and ultrastructural studies it has been suggested that it originates from the Schwann cell. Our recent observation that granular cell tumor is positive with PG-M1, a new anti-macrophage monoclonal antibody, led us to further investigate the immunophenotypic profile of the tumor.
Study Design: We studied 11 granular cell tumors using a panel of 20 antibodies, 13 monoclonal and 7 polyclonal.
Results: The immunohistochemical study showed in all cases a constant diffuse positivity for S-100 protein, neuron-specific enolase, vimentin, KP1 and PG-M1, as well as occasional and focal positivity for alpha-1-antitrypsin, alpha-1-antichymotrypsin and lysozyme.
Conclusions: The immunophenotypic profile constantly observed could be the expression, on one hand, of the neuroectodermic nature of the neoplasm, proven by positivity for S-100 protein, neuron specific enolase and vimentin, and on the other could be the expression of the phagocytic activity of the tumor cell, proven by positivity for KP1 and PG-M1 antibodies and also by the presence of numerous phagolysosomes.