History
A 425-kg (935-lb) bay yearling Thoroughbred filly at a stud farm was examined because the horse had a tendency to remain recumbent (reluctant to stand) and had a hemorrhagic discharge from the vulva. The hemorrhagic discharge had been noticed a few weeks previously when the filly was being prepared for race training. Initial differential diagnoses included abdominal or gastrointestinal discomfort (colic), urinary or reproductive tract inflammation with hemorrhage, and vaginal varicosities.1
Examination revealed that the filly had a dull mentation but was responsive to stimuli. Heart rate was 60 beats/min, respiratory rate was 30 breaths/min, and rectal temperature was 38.3°C (100.9°F); mucous membrane color and capillary refill time were considered normal; and results of auscultation of the gastrointestinal tract were within anticipated limits. There was obvious serosanguineous discharge emanating from the vulva that was also present on the tail and perineum.
To facilitate further examination, the filly was sedated by IV administration of xylazine hydrochloridea (100 mg), butorphanol tartrateb (10 mg), and diazepamc (5 mg).
Speculum examination revealed pink-red fluid visible at the vestibulovaginal junction, with no abnormalities in the vagina or at the cervix. Administration of hyoscine-N-butylbromided (20 mg, IV) facilitated per rectum palpation of the abdomen, which revealed a rubbery mass in the left caudodorsal region. Per rectum ultrasonography revealed a tubular 8-cm-diameter heterogeneous mass within the left horn of the uterus (Figure 1). Hysteroscopye revealed an intrauterine lobulated mass that varied from gray-white to dark red–purple (Figure 2); the mass was located immediately cranial to the cervix. The main differential diagnosis for the mass was neoplasia.2
Ultrasonographic image of a variably echogenic mass detected in the left horn of the uterus of a yearling Thoroughbred filly with hemorrhagic discharge from the vulva. Distance between caliper markers (plus signs) is 8 cm.
Citation: Journal of the American Veterinary Medical Association 254, 8; 10.2460/javma.254.8.925
Hysteroscopic image of a verrucous multicolored mass detected in the left horn of the uterus of the filly of Figure 1.
Citation: Journal of the American Veterinary Medical Association 254, 8; 10.2460/javma.254.8.925
Question
What is the most commonly reported neoplasm in the uterus of mares? Please turn the page.
Answer
Leiomyoma.
Results
To characterize the tumor, a sample was collected by manually removing a portion of the mass (Figure 3). The sample was placed in neutral-buffered 10% formalin solution and submitted for histologic examination.
Photograph of a manually collected sample of the intrauterine mass in the filly of Figure 1. The sample was submitted for histologic examination.
Citation: Journal of the American Veterinary Medical Association 254, 8; 10.2460/javma.254.8.925
The following morning, the filly had signs of colic and was pyrexic (39.2°C [102.6°F]). It was believed that this response may have been caused by the release of bacteria from the tumor as well as the possible effects of sepsis attributable to hysteroscopy. The filly responded favorably to palliative treatment with flunixin megluminef (500 mg, IV, once) and a 3-day course of penicillin G procaineg (9,000 mg, IM, q 12 h), gentamicinh (3,000 mg, IV, q 24 h), oxytocini (10 U, IM, q 6 h), and phenylbutazonej (1,000 mg, PO, q 12 h).
Histologic examination by a veterinary pathologist revealed that the mass was composed of stromal tissue traversed by relatively uniform small spindle to stellate cells in diffuse sheets of various cell densities. Nuclei were relatively uniform. Cells in sheets were interspersed with edematous areas that had cells arranged in a meshwork among vacuolated stroma. There were many capillaries. Rare, residual, often mildly cystic glands and surface epithelium were visible in some places. Large areas were necrotic as a result of ischemia from vascular thrombosis, with many bacteria in thrombosed vessels and on the surface infiltrating throughout the necrotic tissue. Intense fibrinopurulent inflammation with hemorrhagic fibrinous necrotic inflammatory exudate was visible on the luminal surface. Mitotic figures were rarely seen (Figure 4).
Photomicrographs at a lower (A) and higher (B) magnification of tissue sections from a juvenile polypoid endometrial stromal tumor in the uterus of the filly in Figure 1. H&E stain; bar = 5 μm in panel A and 0.5 μm in panel B. (Photographs courtesy of Laverty Vetnostics. Printed with permission.)
Citation: Journal of the American Veterinary Medical Association 254, 8; 10.2460/javma.254.8.925
Immunohistochemical analysis revealed spindle-shaped tumor cells with positive staining for vimentin and desmin but negative staining for factor VIII. This confirmed a mass of muscle origin, rather than endothelial origin. An initial diagnosis of juvenile uterine leiomyoma with secondary necrosis, bacterial infection, and severe inflammation was made. A comment in the pathology report indicated that the bacteria could have been anaerobes. On subsequent review by the same veterinary pathologist, the mass was reclassified as a juvenile polypoid endometrial stromal tumor.
Seventeen days after collection of the sample that was submitted for histologic examination, the mass was removed by per vaginum transcervical manual debridement. The filly was sedated, and antimicrobials and an NSAID were prophylactically administered, similar to when the sample of the mass was collected. Approximately 50-cm3 segments were removed by manually debriding friable portions from the mass with digital pressure (Figure 5). Total wet weight of the tumor was > 2.5 kg (> 5.5 lb).
Photograph of the > 2.5-kg (> 5.5-lb) mass manually removed from the uterus of the filly in Figure 1.
Citation: Journal of the American Veterinary Medical Association 254, 8; 10.2460/javma.254.8.925
Eight days after tumor removal, the reproductive tract of the filly was reexamined by per rectum palpation, per rectum ultrasonography, and hysteroscopy. A blood clot was detected in the uterine lumen and was removed manually. The remnant of a pedicle on the dorsal wall of the left uterine horn was also detected (Figure 6) and manually debrided.
Hysteroscopic image of the pedicle remnant on the dorsal wall of the left uterine horn of the filly in Figure 1 that was seen 8 days after removal of the juvenile polypoid endometrial stromal tumor.
Citation: Journal of the American Veterinary Medical Association 254, 8; 10.2460/javma.254.8.925
Fifteen days after tumor removal, the reproductive tract of the filly was reexamined. Ultrasonography revealed a large (43 mm) follicle on the left ovary and uterine edema, but no intrauterine fluid was detected. Hysteroscopy revealed that the mucosa of the uterine lumen mucosa was unremarkable and appeared healthy (Figure 7).
Hysteroscopic image of the uterine bifurcation (b) and openings of the left (L) and right (R) uterine horns of the filly in Figure 1 at 15 days after removal of the juvenile polypoid endometrial stromal tumor. Notice the endometrial fold (e) in the body of the uterus.
Citation: Journal of the American Veterinary Medical Association 254, 8; 10.2460/javma.254.8.925
Discussion
Neoplasia is typically rare in young animals. Neoplasms of the reproductive tract of mares are uncommon, and uterine tumors are rare. Uterine masses include benign neoplasms2 (leiomyoma, fibroma, fibroleiomyoma, and endometrial stromal tumor3) and juvenile polyps.4 Malignant uterine neoplasms include leiomyosarcoma, rhabdomyosarcoma, lymphosarcoma, adenocarcinoma, and metastatic tumors. Leiomyoma is the most common uterine tumor in mares. Leiomyomas can differ in size, shape, number of masses, and location within the uterus.2
A commonly reported clinical sign in mares with a uterine tumor is hemorrhagic discharge from the vagina (exiting the vulva).1 However, hemorrhagic discharge from the vulva might not be the result of a neoplasm.
Hemorrhagic discharge from the vulva could be attributable to abnormalities in the urinary or reproductive tracts. Thus, a thorough examination that might include use of a speculum for vaginal examination, per rectum palpation and ultrasonography, endoscopy, and other tests (such as examination of biopsy specimens, hematologic evaluations, and biochemical analyses) should be undertaken as deemed necessary for each patient.
In mares, the most common reason for hemorrhagic discharge from the vulva is bleeding of vestibulovaginal varicosities.1 There is a report5 of hemorrhagic discharge from the vulva of a mare with a leiomyoma. In young horses, a leiomyoma in 2 paternal half-sibling yearling Appaloosa fillies6 and a 2-year-old Arabian filly,7 endometrial stromal hyperplasia in a yearling Quarter Horse,3 and endometrial polyps in a yearling Thoroughbred filly4 have been reported.
The clinical signs as well as the characteristics of the mass detected in the filly described here were extremely similar to those reported for 3 other fillies with tumors.3,4,7 All 3 of those fillies had hemorrhagic discharge from the vulva. The tumors were friable, pedunculated, verrucous masses, and all had markedly similar histopathologic features. It is likely that all 4 fillies had the same type of tumor. Clarification of tumor classification is needed.
It has been suggested that such tumors could be a result of peripubertal hormonal influences on the endometrium of genetically predisposed animals,7 but there is insufficient evidence to substantiate this supposition.
To the author's knowledge, the mass described here represented the first case of a juvenile polypoid endometrial stromal tumor in the uterus of a yearling Thoroughbred filly that was successfully removed by per vaginum transcervical manual debridement. This indicated that more invasive surgical procedures (eg, laparotomy for hysterectomy or hysterotomy) were not required for successful management of the tumor in this filly.
Outcome
The filly was discharged to the owner, and she began her flat-track racing career, which terminated with a win after 7 years. The horse was then retired to barrel racing. No reproductive examinations were performed on the horse after she began her flat-track racing career; however, the owner and trainer noted no abnormalities during this time.
Acknowledgments
No external funding was used in this study. The author declares that there were no conflicts of interest.
The author thanks Lee-Anne McInerny for technical assistance; Dr. Angela Begg for assistance with the histologic evaluation, histopathologic description, and determination of the diagnosis; and Dr. Kristen Todhunter for assistance with the photography.
Footnotes
Ilium Xylazil-100, 100 mg/mL, Troy Laboratories Pty Ltd, Smithfield, NSW, Australia.
Ilium Butorgesic, 10 mg/mL, Troy Laboratories Pty Ltd, Smithfield, NSW, Australia.
Ilium diazepam injection, 5 mg/mL, Troy Laboratories Pty Ltd, Smithfield, NSW, Australia.
Buscopan, 4 mg/mL, Boehringer Ingelheim Pty Ltd, North Ryde, NSW, Australia.
Olympus 120-cm gastroscope, Olympus Australia Pty Ltd, Notting Hill, VIC, Australia.
Ilium Flunixil, 50 mg/mL, Troy Laboratories Pty Ltd, Smithfield, NSW, Australia.
Propercillin, 300 mg/mL, Troy Laboratories Pty Ltd, Glendenning, NSW, Australia.
Ilium Gentam 100, 100 mg/mL, Troy Laboratories Pty Ltd, Smithfield, NSW, Australia.
Ilium Syntocin, 10 U/mL, Troy Laboratories Pty Ltd, Glendenning, NSW, Australia.
Bute Paste, 200 mg/mL, Ranvet Ltd, Banksmeadow, NSW, Australia.
References
1. Frazer GS. Differential diagnosis for vaginal haemorrhage in the mare. Equine Vet Educ 2005;17:153–155.
2. McCue PM. Neoplasia of the female reproductive tract. Vet Clin North Am Equine Pract 1998;14:505–515.
3. Murphy JE, Frazer G, Munsterman A, et al. Endometrial stromal hyperplasia and mass formation in a yearling Quarter Horse. Equine Vet Educ 2005;17:159–162.
4. Yamini B, Borg L. Endometrial polyps and endometritis in a Thoroughbred filly. J Vet Diagn Invest 1994;6:496–498.
5. Brandstetter LR, Doyle-Jones PS, McKenzie HC III. Persistent vaginal haemorrhage due to a uterine leiomyoma in a mare. Equine Vet Educ 2005;17:156–158.
6. Romagnoli SE, Momont HW, Hilbert BJ, et al. Multiple recurring uterocervical leiomyomas in two half-sibling Appaloosa fillies. J Am Vet Med Assoc 1987;191:1449–1450.
7. Broome TA, Allen D, Baxter GM, et al. Septic metritis secondary to torsion of a pedunculated uterine fibroleiomyoma in a filly. J Am Vet Med Assoc 1992;200:1685–1688.
