Epidemiological Aspects and Differential Diagnosis of the Cutaneous Round Cell Tumors in Dogs

Round cell neoplasms (RCNs) are frequent cutaneous lesions in dogs, with high percentages among skin tumors. In this category are included histiocytoma, mast cell tumor, plasmacytoma, lymphoma and transmissible venereal tumor. The aim of the study was to perform an epidemiological study with reference to the cutaneous round cell tumors in a period of 10 years in the Department of Pathology (Faculty of Veterinary Medicine, Cluj-Napoca, Romania). Additionally, in the recorded cases with round cell tumors (mast cell tumor, histiocytoma and lymphoma) we described the main histological and cytological features. The epidemiological data were collected from the records of Pathology Department between 2005-2014. The investigation included dogs diagnosed with cutaneous round cell neoplasms, following necropsy analysis or assessment of biopsies or cytological samples. All collected specimens were analyzed by histopathological and/or cytological techniques. The staining used for histological investigation were Hematoxylin-eosin, Masson’s trichrome and Toluidine blue, whereas Diff Quik and Wright methods were utilized in cytological specimens. The distribution of the cutaneous round cell tumors in relation to age, breed and sex was also assessed. The most frequent round cell tumor type was the mast cell tumor (19.54%) followed by histiocytoma (11.33%) and lymphoma (1.98%). The round cell tumors recorded were equally distributed in both males and females. Concerning the distribution of cutaneous RCNs by age (average age), histiocytoma occurred in 5 years old subjects, mast cell tumor in 11.9 years old subjects, and lymphoma in 6 years old subjects. Mast cell tumor was more frequent in stray dogs and Boxer breed, while histiocytoma occurred more commonly in stray dogs. Histological and cytological analysis was mandatory to perform the differential diagnosis between RCNs. Microscopic details concerning cytoplasm and nucleus of tumoral cells, together with the displaying mode in histological specimens may reveal the type of RCN. Cutaneous round cell tumors had an increased incidence, aspect observed in other reports too. The differential diagnosis has to rely on some specific microscopical features that can suggest the type of RCN.