Granulosa cell tumor and prolonged estrus in a Boxer bitch

An 11 year old, multiparous Boxer bitch was presented to the Virginia-Maryland College of Veterinary Medicine Theriogenology Service for evaluation of persistent vulvar swelling and bloody vulvar discharge of 34 days duration. On physical examination, the vulva was markedly swollen, with a small amount of blood-tinged discharge. Vaginal cytology revealed 100% superficial epithelial cells, confirming a diagnosis of estrogen influence. Thorough history revealed no known exposure to exogenous estrogens. Abdominal ultrasonography was performed to identify potential structural abnormalities of the reproductive tract and/or adrenals which could be responsible for estrogen influence. Ultrasonography revealed a markedly thickened myometrium and endometrium, with unremarkable ovaries and adrenal glands. Furthermore, serum progesterone concentrations via chemiluminescence were1.02 ng/ml. Based on the clinical findings, our differential diagnoses were microscopic disease of the ovary or exogenous estrogen exposure. Because the bitch had no history of exogenous estrogen exposure, microscopic ovarian disease, such as a granulosa cell tumor, was considered to be the most likely differential. Despite ovarian neoplasia being rather uncommon, granulosa cell tumors account for approximately half of all ovarian tumors in bitches. 1 It is not unusual for granulosa cell tumors to produce estrogen and therefore cause clinical signs consistent with a prolonged estrus. Definitive diagnosis of granulosa cell tumors relies on histopathology of ovaries. The owner elected not to pursue recommended ovariohysterectomy and instead elected humane euthanasia due to orthopedic comorbidities, with postmortem necropsy. Histopathology of a small (2 mm in diameter) round mass within an ovary revealed a well demarcated, proliferative mass made of tubules and small cysts lined with foamy basophilic cells, consistent with a granulosa cell tumor. This case demonstrated the importance of considering microscopic disease when presented with a bitch exhibiting prolonged estrus.

Keywords: Granulosa cell tumor, prolonged estrus, ovarian neoplasia, bitch

Reference

1.White RN, Brearley M: BSAVA manual of canine and feline oncology. Dobson J, Lascelles D. Gloucester, England: British Small Animal Veterinary Association; 2016. p. 248-264.

This manuscript was originally published in the journal Clinical Theriogenology Vol 12(3) Sept 2020.  Clinical Theriogenology is the official journal of the Society for Theriogenology (SFT) and the American College of Theriogenologists (ACT).  This content has been reproduced on the IVIS website with the explicit permission of the SFT/ACT.