Canine laryngeal rhabdomyosarcoma: An immunohistochemical and electron microscopic study.

Abstract

A neoplasm composed of sheets of variably sized, highly pleomorphic cells was removed from the larynx of a Doberman pinscher dog. Using immunohistochemical methods, tumor cells showed strong reactivity for desmin, myoglobin, and actin, weak reactivity for vimentin, and failed to stain for high or low molecular cytokeratins, epithelial membrane antigen, or myosin. The dominant ultrastructural feature was the abundance of mitochondria with densely-packed cristae, virtually filling the cytoplasm in some of the cells. Careful scrutiny of the electron micrographs revealed irregular dense areas in the cytoplasm similar to Z-band material. Although initial histopathologic and ultrastructural examinations suggested that the neoplasm was an oncocytoma, a definitive diagnosis of rhabdomyosarcoma was made on the basis of immunohistochemical and ultrastructural determinations.