Prostatic wash fluid from a 14 year-old, male-castrated, Pomeranian. The poor little dog presented for evaluation of frequent, but rather unproductive, attempts at urination. On rectal examination he had a markedly enlarged prostate…
The fluid was incredibly cellular, with many large clusters of epithelial cells found. While some transitional cells or prostatic glandular cells should exfoliate with a wash, you should never get too many cells. Or cells that look like THIS. Marked criteria for malignancy, including prominent anisocytosis (look at all that size variation) and anisokaryosis (there are some mammoth nuclei in there). Neoplastic prostatic glandular cells can also produce tons of secretory product, often collection in little, clear vacuoles - see all those clear, circular structures in the cytoplasm?
Tons of extracellular magenta material was also present in the slide. What could that be? Secretory product for the tumor cells? Nope - that material is lubricant! It would be absolutely inhumane to run a catheter up there without lube :-P Any hydrous gel (like lube or ultrasound gel) will act like a sponge for stain, and can sometimes obscure the tumor cells.
Final diagnosis: prostatic carcinoma. Cancer in the most common cause of prostatomegaly in a castrated dog. However, if they are intact, benign prostatic hyperplasia or prostatitis are most common. The patient is currently receiving chemotherapy, but I have little information on his progress.