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SUMMARY Records of 411 cases of malignant oral and pharyngeal neoplasia in dogs seen at the University of Pennsylvania Veterinary Hospital between 1952 and 1976 were reviewed. The most common tumors were squamous cell carcinoma ( scc ; 164), malignant melanoma (121), and fibrosarcoma (76). The median age was 8 years for dogs with fibrosarcoma, 9 years for dogs with nontonsillar scc , 10 years for dogs with tonsillar scc , and 12 years for dogs with malignant melanoma. Oral tumors were more common in males. Smaller breeds tended to develop malignant melanomas and tonsillar scc , whereas larger breeds had more fibrosarcomas and nontonsillar scc . The gingiva was the most common site for malignant melanoma and fibrosarcoma, and the tonsil was the most common site for scc . Gingival tumors were evenly divided among the three tumor types, but 76% of labial or buccal mucosal tumors were malignant melanomas. Gingival fibrosarcomas were more often located in the maxillary arcade. Gingival scc were most often located rostral to the canine teeth. Radiographic evidence of thoracic metastasis was seen in 14% of malignant melanomas, 10% of fibrosarcomas, 8% of tonsillar scc , and 3% of nontonsillar scc at the time of diagnosis; however, necropsy findings indicated there were at least 13% false-negative thoracic radiographs in dogs with malignant melanoma. For more than one half of all gingival tumors, bone invasion was evident on occlusal radiography. At necropsy, 81% of malignant melanomas, 77% of tonsillar scc , and 35% of fibrosarcomas had metastasized to or beyond regional lymphnodes. In dogs treated with conventional surgery or radiation therapy, the major cause of treatment failure was recurrence of tumor at the primary site.
Todoroff et al. (Sat,) studied this question.