The first patient is a seven-year-old, neutered male, Labrador retriever that was rescued in Turkey. He presented to a hospital in Virginia with a large ulcerated mass located on the penis that was malodorous and oozing purulent-looking material. A tissue imprint of the mass was obtained and sent to EVP for a diagnosis. See figures 1 & 2 below.
The second patient is a one-year-old, spayed female, terrier mix that was spayed in Guatemala six months ago. She presented to a hospital in Maryland with a large solid mass within the vagina. The patient also had a history of bloody vaginal discharge and cystitis. A fine needle aspiration of the mass was performed and slides were sent to EVP for a diagnosis. See figure 3 below.
Figure 1 (from penis of case 1) – Tissue imprint: Several large individual round cells surrounded by numerous neutrophils with one well-differentiated squamous epithelial cell (8 o’clock position from the center).
Figure 2 (from penis of case 1) – Tissue imprint: Few large individual round cells surrounded by many neutrophils and occasional extracellular bacteria.
Figure 3 (from vagina of case 2) – FNA: Numerous individual round cells with one mitotic figure and few neutrophils.
Both cases consist of individual round cells with a small to moderate amount of light gray cytoplasm that commonly contains numerous clear punctate vacuoles. This cytoplasm surrounds a centrally located round to oval nucleus with a coarsely stippled, commonly referred to as “ropey”, nuclear chromatin with occasional visible nucleoli of variable size. Mitotic figures are commonly found and can be bizarre in appearance (see figure 3). The diagnosis for both cases is transmissible venereal tumor (TVT). As with case one, these tumors commonly become ulcerated and are associated with numerous neutrophils and intracellular and/or extracellular bacteria. In these cases of ulcerated tumors, fine needle aspiration is always preferred over an impression smear, to maximize exfoliation of the tumor cells and to minimize superficial constituents such as neutrophils and bacteria, similar to case one (the diagnosis was still easily made for case one, but slides were not as homogeneously cellular, as in case two).
TVT is obviously a transmissible tumor that has been reported worldwide, but is much more prevalent in tropical or subtropical areas were dogs are allowed to run free/minimal population control. In the author’s experience, cases of TVT found in the northeastern United States most certainly in dogs that have traveled from other regions of the world or possibly the most southern parts of the eastern US (Gulf Coast). Although most commonly found on genitalia or the rostral parts of the face, lesions can also be found in cutaneous locations and can metastasize, typically in malnourished or immunocompromised dogs.
As highlighted in the photos and in the description above, TVT is one of the five round cell tumors that can be identified cytologically. At first glance, TVT cells resemble histiocytes due to their abundant light gray cytoplasm. But hallmark features of these cells include the punctate cytoplasmic vacuoles and the coarse nuclear chromatin pattern, as well as frequent mitotic figures.
No follow-up information was obtained for case one, but case two was treated and “cured” with four doses of vincristine.
Clinical Pathologist & CEO
Knoxville, TN & Bethesda, MD
Jubb, Kennedy, and Palmer’s Pathology of Domestic Animals, 6th Ed. Volume 3, Edited by M. Grant Maxie, 2016.
Canine and Feline Cytology, A Color Atlas and Interpretation Guide, 3rd Ed. RE Raskin and DJ Meyer, 2016.