AN IMMUNOHISTOCHEMICAL STUDY OF 3 EQUINE PULMONARY GRANULAR-CELL TUMORS

Granular cell tumor (GCT) is a morphologic designation for tumors of v aried histogenesis. Most GCTs in human beings are derived from Schwann cells, and rat meningeal GCTs are believed to originate in the neural crest. Three equine pulmonary GCTs from aged horses were studied immu nohistochemically with primary antibodies directed against vimentin, c ytokeratins (AE1/AE3), S-100, Leu 7, desmin, and neuron-specific enola se (NSE) using a steptavidin-biotin procedure. All three tumors staine d similarly with strong and diffuse staining of neoplastic cells for v imentin and S-100 and negative staining with all other antibodies. On the basis of the immunohistochemical results and the previously descri bed histologic and ultrastructural characteristics, equine pulmonary G CT is designated as neural crest and possibly Schwann cell derived, si milar to GCT in rats and human beings.