Reports of prognosis based on clinical staging of canine oral malignant melanoma consistently differ. To determine the prognostic utility of the World Health Organization (WHO) tumour, node, metastasis (TNM) system and a proposed alternative staging system, a retrospective study of 41 dogs with naturally occurring oral malignant melanoma was conducted. All the tumours were clinically staged, removed surgically and the tissues histologically reviewed. Treatment responses were correlated with the clinical and histological features reported to have prognostic utility. Dogs presenting with a tumour smaller than 8 cm3, located on the rostral mandible or caudal maxilla, and, or, having a tumour mitotic index of 3 or less had a significantly longer remission length and survival time than did other dogs, regardless of the treatment selected. Treatment by radical surgical excision (eg, hemimandibulectomy) resulted in longer remission lengths and survival times than any other type of treatment regardless of whether or not surgical margins were determined to be free of residual tumour. The WHO system failed to identify a prognostic difference between dogs of a differing clinical stage. An alternative system derived from significant features mentioned above did identify a prognostic difference and is recommended for further evaluation regarding its utility in the pre‐treatment evaluation and clinical staging of other dogs with oral ‐malignant melanoma.

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Abstract. To determine the diagnostic and/or prognostic importance of chromosomal aberrations identified in dogs with malignant (non-Hodgkin's) lymphoma, clinical stages for 6 1 dogs with lymphosarcoma were determined, the lymph node(s) were histopathologically graded, and the malignant tissue lymphocytes were karyotyped. The results from life table survival curve analysis demonstrated that first remission length and survival time were significantly longer in 15 of 6 1 (25%) dogs that had a trisomy of chromosome 13 as the primary chromosomal aberration than in those dogs (46/61, 75%) with other primary chromosomal aberrations ( P < 0.05). Sex, age, weight, histopathologic subtype and grade, World Health Organization (WHO) clinical stage, WHO and modified Karnofsky performance status, chromosomal modal number, and treatment protocol were of no prognostic importance in predicting first remission length or survival time ( P > 0.05). Multivariate analysis did not identify a significant correlation between the prognostic groups or within the various prognostic subsets (P > 0.05). The pathogenesis of canine and human non-Hodgkin's lymphoma, as observed cytogenetically, differs.

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