Luciana Mandrioli

C-kit Gene Product (CD117) Immunoreactivity in Canine and Feline Paraffin Sections

CD117 is a transmembrane tyrosine kinase growth factor receptor expressed by a variety of normal human cell types, including germ cells, immature myeloid cells, and mast cells. To evaluate the pattern of CD117 expression in dogs and cats, we applied a polyclonal antibody on paraffin sections from 44 samples of normal tissues and 104 tumors. In both species, strong immunoreactivity was observed in mast cells, interstitial cells of Cajal, and in mast cell tumors. Among gastrointestinal mesenchymal neoplasms, tissues from five dogs and one cat revealed strong CD117 expression, enabling us to identify them as gastrointestinal stromal tumors (GISTs).

Malignant, solitary, nasopharyngeal schwannoma in a cow

plump cells did not show distinct cellular outlines; they had a single, oval to ellipsoid central vesicular nucleus, and one to two well-distinct central nucleoli. Mitotic figures were present at one to two per high power field; sparse lymphocytes infiltrated the thickest intratumoural connective septa. Immunohistochemically, a diffuse strong S-100 protein immunoreactivity was observed in the cytoplasm and occasionally in the nucleus of neoplastic cells (Fig 4). The same cells also showed a cytoplasmic immunopositivity for vimentin, while neuron-specific enolase, desmin, actin, widespectrum cytokeratin and CD34 were negative. Pieces of formalin-fixed tissues were fixed in 2·5 per cent glutaraldehyde, postfixed in 1 per cent osmium tetroxide, rinsed in cacodylate buffer solution, dehydrated and embedded in acrylic resin (Durcupan AcM). Ultrathin sections stained with uranyl acetate and lead citrate and examined using a CM 10 transmission electron microscope (Philips) revealed a basal lamina, a paucity of cytoplasmic organelles and occasional desmosome-like intercellular junctions of the neoplastic cells. Microscopic, immunohistochemical and ultrastructural findings were coherent with a definitive diagnosis of solitary malignant schwannoma. An intranasal mass in a cow can theoretically be related to a chronic inflammatory process (for example, a foreign body reaction or granuloma) or neoplastic process (that is, ethmoidal adenocarcinoma of olfactory epithelium, fibrosarcoma, schwannoma or osteoma) (Radostits and others 2000). In the present case, the cytological and histopathological findings were supported by the S-100 immunopositivity and the ultrastructural findings to suggest a neoplastic process originating from peripheral nerves, that is, a malignant PNST or a malignant solitary schwannoma. The histopathological Antoni type A and type B patterns Malignant, solitary, nasopharyngeal schwannoma in a cow