The presence of tumor within the serosal cavities, often connected with accumulation of serosal effusion, is a quite common problem in the small animal veterinary medicine. The first step in diagnosis of such cases is cytopathological examination. The aim of the present study was to evaluate the usefulness of cytology and immunocytochemistry, using commercially available antibodies (anti-cytokeratin, anti-vimentin, and anti-desmin), in differential diagnosis of malignant tumors located within serosal cavities in dogs. The final cytological diagnosis of carcinoma/adenocarcinoma, sarcoma, and mesothelioma was obtained on the basis of routine cytopathology and immunocytochemistry, and then confirmed by histopathology and immunohistochemistry. Cytoplasmic immunoreactivitiy of normal mesothelid cells and cytoplasmic immunoreactivity of hyperplastic mesothelial cells revealed constant and strong expression of all examined intermediate filaments: cytokeratin, vimentin and desmin. Application of routine cytopathology and immunocytochemistry allowed 32 neoplastic tumors to be detected: 19 cases of carcinomas/adenocarcinomas, 6 cases of sarcomas, 7 cases of mesotheliomas. Immunostaining of cytopathological samples with chosen set of antibodies: anti-cytokeratin, anti-vimentin, anti-desmin is a useful, and low invasive test for differentiation between mesotheliomas and carcinomas/adenocarcinomas in dogs.

In conclusion, routine cytology is a reliable diagnostic method for canine oral amelanotic melanoma and metastatic amelanotic melanoma, and ICC, using anti-cytokeratin, anti-vimentin, and anti-Melan A antibodies, is an excellent supporting method for presurgical diagnosis of poorly differentiated oral malignancies in dogs.

Cytomorphometry made on cytological slides is the quantitative method of precise analysis of cellular structures, including both cytoplasm and nucleus. The aim of this study was to describe cytomorphometric parameters of mesothelial cells in the course of benign reactive and malignant proliferation and to compare them to carcinomas and adenocarcinomas located within serosal cavities in dogs. The second aim was to evaluate applicability of cytomorphometry to diagnostics of diseases causing accumulation of effusion in serosal cavities. Cytological samples of normal and non-malignant mesothelium, mesothelioma and various carcinomas were collected from dogs. Cytomorphometry was made on the smears stained with Giemsa solution. Mean nuclear and cellular perimeter, mean nuclear and cellular area, mean nuclear and cellular diameter, and mean nuclear and cellular roundness were determined. Moreover, nuclear to cytoplasmic ratio (N/C) was calculated. The data revealed statistically significant differences for all parameters, excluding mean nuclear perimeter, between compared groups. Normal mesothelium cells and their nuclei were significantly smaller and more elongated than cells and nuclei of both benign reactive and malignant neoplastic mesothelium. Only a few differences were observed between benign reactive mesothelium cells and mesothelioma cells -mean nuclear area and mean nuclear diameter of benign reactive mesothelium cells were significantly larger and N/C ratio was higher in comparison to mesothelioma cells. Even though some significant differences were observed, considerable overlap of these cytomorphometric parameters in animals with different diseases limited practical role of these observations. Cytomorphometric analysis of cellular samples collected from dogs with proliferative processes affecting serosal cavities can be only an auxiliary method increasing accuracy of preoperative diagnosis.