Page 1381 - Clinical Small Animal Internal Medicine

148 Gynecologic Cancers 1319

malignant tumors or metastatic/high‐grade tumors, typically unilateral but can be found bilaterally. Similar
VetBooks.ir respectively. 2 to dogs, granulosa cell tumors in cats can metastasize
and are hormonally active. Although there are few reports
The use of carbon dioxide laser ablation in conjunction
with doxorubicin chemotherapy(at 30 mg/m intrave-
young animals and rarely metastasize.
nously) every four weeks for a total of two treatments has of teratomas in cats, they have been noted to occur in
been shown to provide long‐term control in one case
report of a poodle with vaginal fibrosarcoma. Epidemiology
Another potential treatment is the use of the proges-
terone receptor antagonist aglepristone, as neoadjuvant As ovarian tumors are extremely rare in both dogs and
therapy prior to surgery for large benign vaginal tumors. cats, the true prevalence is unknown.

Prognosis Signalment
Surgery is often curative for benign tumors and the The majority of ovarian tumors affect older dogs, with
prognosis is guarded for malignant tumors as they have the exception of teratomas. One study found pointers
the potential to metastasize and recur. had an increased risk of developing epithelial tumors
while English bulldogs were at higher risk for granulosa
cell tumors. German shepherds and poodles were
Ovarian Tumors also reported to have a higher occurrence of ovarian
tumors.

Etiology/Pathophysiology
History and Clinical Signs
Ovarian tumors can arise from different locations
within the ovary and are classified based on their origin, The clinical signs reported are variable but may include
such as epithelial cells, sex cord stromal elements of the vaginal discharge, distended abdomen, pyometra, and an
ovary and germ cells. Epithelial tumors are further char- abnormal estrus cycle. If metastasis occurs, clinical signs
acterized as adenoma, cystadenoma, adenocarcinoma, may be associated with the location of involvement, such
and undifferentiated carcinoma. Tumors referred to as as ascites secondary to tumor effusion. As sex cord
sex cord stromal tumors are granulosa cell tumors, tumors can cause hormonal dysfunction, signs associ-
luteomas, and thecomas. Although more common in ated with excess sex hormones (both estrogen and
the male, this group also includes Sertoli, Leydig and progesterone) can be observed. Examples of such
Sertoli‐Leydig cell tumors. Lastly, the germ cell tumors changes include bilateral alopecia, vulvar enlargement,
include dysgerminoma, teratocarcinoma, teratoma, and vaginal bleeding, pyometra, and endometrial hyperpla-
choriocarcinoma. Other rare tumor types include sia. Granulosa cell tumors rarely produce enough sex
hemangiosarcoma, rhabdomyosarcoma, fibrosarcoma, hormone to cause bone marrow aplasia, but rare exam-
and carcinosarcoma. ples of sepsis or bleeding secondary to neutropenia and
The majority of ovarian tumors, regardless of their his- thrombocytopenia have been reported.
tologic subtype, are unilateral. However, adenocarcino-
mas and mixed sex cord stromal tumors (specifically Diagnosis
Sertoli‐Leydig cell tumor) can occur bilaterally in about
30% of cases. The rates of occurrence for each type varies Although the metastatic rate for ovarian tumors is rela-
depending on the study, but granulosa cell tumors and tively low, it is still recommended that thorough staging
epithelial tumors account for most ovarian tumors in is performed including complete blood count, biochem-
dogs and granulosa cell tumors are the most common istry, three‐view thoracic radiographs, and abdominal
ovarian tumor found in cats. ultrasound. An ultrasound is especially important to
The overall metastatic rate for ovarian tumors in dogs help evaluate for local metastasis to regional lymph
is approximately 25%, with a higher incidence, approxi- nodes, surrounding organs, and peritoneum. It is not
mately 50%, in both adenocarcinomas and teratomas. recommended that ultrasound‐guided cytology/biopsy
Sex cord tumors are the only histologic type that has the be performed. If the tumor is malignant, seeding or
potential of being hormonally active, as they arise from translocation of the tumor cells can occur. If histopathol-
gonadal tissue of the ovary and can produce steroid ogy cannot differentiate tumor type, the use of immuno-
hormones. histochemistry may be helpful. HBME‐1 (and cytokeratin
In cats, the most common ovarian tumor is granu- 7) and inhibin‐alpha are useful markers to confirm epi-
losa cell tumor, followed by dysgerminomas. They are thelial and sex cord stromal tumor origin, respectively.