Veterinary Medicine - June 2008 - (Page 296)

Clinical Exposures illuminating images from patient files PEER-RE VIE WED Canine transmissible venereal tumor: The cytologic clues Rob Simoni, DVM, and Joyce S. Knoll, VMD, PhD, DACVP 3-year-old castrated male Labrador retriever with a history of blood dripping from its penis was referred to the Foster Hospital for Small Animals at the Cummings School of Veterinary Medicine at Tufts University. The dog had been adopted from a breed rescue group about six weeks before presentation. Before being acquired by the rescue group, the dog had lived in Texas and Tennessee. Bloody penile discharge had been noted since the adoption, although the new owners reported that it had initially seemed to resolve without any intervention. A DIAGNOSIS On physical examination, a large mass was noted on the shaft of the penis (Figure 1). The remainder of the physical examination ﬁndings were unremarkable. Cytologic examination of impression smears made from tissue excised from the mass revealed a markedly cellular sample with a predominant population of homogeneous, discrete round cells with mild anisocytosis and anisokaryosis (Figure 2). These cells had a moderate amount of pale-blue cytoplasm, often containing a few small punctate vacuoles. The nuclei were round with coarse chromatin and a single prominent nucleolus. Moderate mitotic activity was observed (0 to 2/50X ﬁeld) (Figure 3). Occasional neutrophils, lymphocytes, plasma cells, and squamous cells were noted in the background, as were variable numbers of erythrocytes. The cytologic diagnosis was transmissible venereal tumor. 1. Complete extrusion of the penis from the preputial sheath in a 3-year-old Labrador retriever revealed a large, friable, bloody, cauliﬂower-like mass in the region of the bulbus glandis. (Photo courtesy of Tanya Hall, DVM.) Plasma cell Neutrophil TREATMENT The dog was treated weekly with intravenous vincristine. A dramatic reduction in tumor size occurred after the ﬁrst dose, with complete tumor remission after seven doses. The dog was tumor-free at its last recheck one month after the last vincristine injection. 2. An impression smear from the mass shown in Figure 1 reveals numerous discrete round cells with a moderate nuclear to cytoplasmic ratio, grainy light-blue cytoplasm, and round nuclei. Note the punctate cytoplasmic vacuoles and the prominent singular nucleoli. These cells are relatively large, compared with an adjacent neutrophil. In comparison with these cells, the plasma cell has darker, more tightly condensed chromatin and darker-blue cytoplasm that lacks vacuoles (Wright’s- Giemsa stain; 50X). DISCUSSION Canine transmissible venereal tumor, also called Sticker’s sarcoma, is a naturally occurring, horizontally transmitted round cell tumor This case report was provided by Rob Simoni, DVM, and Joyce S. Knoll, VMD, PhD, DACVP, Department of Biomedical Sciences, Cummings School of Veterinary Medicine, Tufts University, North Grafton, MA 01536. 296 June 2008 VETERINARY MEDICINE

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Veterinary Medicine - June 2008 Contents Leading Off Clinical Exposures Idea Exchange A Challenging Case: Conjunctival Lymphoma in a Cat Updates on Canine Hypoadrenocorticism Product Preview CE Form Advertiser Index Marketplace/Classifieds Mind Over Miller Clinical Edge - June 2008 Table of Contents Managing Diabetes Mellitus in Cats: What Makes it Work? Porcine Insulin Zinc Suspension in the Management of Feline Diabetes Mellitus Monitoring Diabetes Mellitus in Diabetic Cats Feline Diabetes Mellitus: Important Client Communication Points

Veterinary Medicine - June 2008

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