Canine laryngotracheal plasma cell tumors: Ten cases and literature review.

Canine extramedullary plasma cell tumors (EMPs) most commonly arise in the skin, oral cavity, rectum, and colon. This retrospective study describes the histopathological and immunohistochemical characteristics and associated clinical signs and outcomes of laryngeal and tracheal EMPs in dogs. Five tracheal and 5 laryngeal EMPs were diagnosed at the Penn Vet Diagnostic Laboratory. Clinical information was obtained via submission forms and follow-up questionnaires. All dogs were male (9 castrated), 7 to 15 years old, and of different breeds. Neoplasms were composed of well-differentiated (n = 6) or moderately differentiated (n = 4) neoplastic plasma cells arranged in sheets, cords, and packets. All neoplasms labeled positively for MUM-1, negatively for PAX5, and were variably CD20- and CD79b-positive. There was no recurrence or disease progression 2 months to 7 years post biopsy in 6/9 cases. Results suggest that surgical resection can result in positive outcomes. Further studies are needed to identify factors leading to progression of this disease.