An immunohistochemical study of three equine pulmonary granular cell tumors

Granular cell tumor (GCT) is a morphologic designation for tumors of varied 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 immunohistochemically with primary antibodies directed against vimentin, cytokeratins (AE1/AE3), S-100, Leu 7, desmin, and neuron-specific enolase (NSE) using a steptavidin-biotin procedure. All three tumors stained similarly with strong and diffuse staining of neoplastic cells for vimentin and S-100 and negative staining with all other antibodies. On the basis of the immunohistochemical results and the previously described histologic and ultrastructural characteristics, equine pulmonary GCT is designated as neural crest and possibly Schwann cell derived, similar to GCT in rats and human beings.