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Gynecologic Cancers
Trina Hazzah, DVM, DACVIM (Oncology)

VCA West Los Angeles Animal Hospital, Los Angeles, CA, USA

Uterine Tumors Epidemiology
The incidence of uterine tumors is less than 0.5% in dogs
Etiology/Pathophysiology and approximately 1% in cats. BHD is inherited through

Uterine cancer is extremely rare in dogs and cats. This is an autosomal dominant pattern.
in part because the overwhelming majority of pets are
spayed. Leiomyoma is the most common uterine tumor Signalment
in the dog, followed by leiomyosarcoma. Other types of
tumors have been reported such as fibroma, lipoma, Uterine tumors typically occur in middle‐aged to older
hemangiosarcoma, fibrosarcoma, angiolipoleiomyoma, dogs and cats, but there are reports in dogs under 1 year
adenoma, adenocarcinoma, and extramedullary plasma- of age. These tumors are overwhelmingly more common
cytoma. In women, estrogen is considered to be the in intact females, but there are reports of uterine stump
primary factor in the development of uterine carcinoma. carcinomas in spayed females. There is no specific breed
It is believed that both endogenous and exogenous predilection.
estrogen can result in endometrial hyperplasia. It also
potentiates the transformation of endometrial hyperpla- History and Clinical Signs
sia to endometrial carcinoma. Estrogen is not the under-
lying hormone responsible for endometrial changes in Most dogs and cats with uterine tumors are asympto-
dogs. In fact, it is progesterone that plays a large role in matic. However, purulent to hemorrhagic vaginal dis-
both neoplastic and nonneoplastic gynecologic diseases charge, lethargy, anorexia, constipation, and pyometra
of the dog. Dogs develop cystic endometrial hyperplasia can occur. Other signs may be associated with the
which is much less likely to transform into carcinoma. metastatic lesions themselves.
The most common uterine tumor in the cat is adeno-
carcinoma which arises from the endometrium. Although Diagnosis
much rarer, leiomyoma, leiomyosarcoma, hemangioma,
squamous cell carcinoma, and carcinosarcoma have A minimum database including complete blood count,
been reported. An association of feline leukemia virus biochemistry, and urinalysis is recommended for any
(FeLV) and the development of uterine adenocarcinoma animal with potential gynecologic cancer. Abdominal
in cats have been reported. radiographs may reveal a mass effect in the caudal
Birt–Hogg–Dubé (BHD) syndrome is a rare inherited abdomen. To thoroughly evaluate the extent of disease
condition that occurs in German shepherd dogs result- or for the presence of regional metastasis, an abdominal
ing from a mutation in the canine orthologue (folliculin) ultrasound is required. Although the majority of uterine
tumor suppresser gene. It manifests in multiple uterine tumors are benign in the dog, three‐view thoracic
leiomyomas, bilateral renal cystadenocarcinomas, and radiographs should be performed. In cats, thoracic
nodular dermatofibrosis. A similar BHD syndrome has radiographs and abdominal ultrasound are mandatory
been noted to occur in humans. as malignant uterine tumors are associated with a high

Clinical Small Animal Internal Medicine Volume II, First Edition. Edited by David S. Bruyette.
© 2020 John Wiley & Sons, Inc. Published 2020 by John Wiley & Sons, Inc.
Companion website: www.wiley.com/go/bruyette/clinical