Ovarian Tumors

GENERAL CONSIDERATIONS

General Considerations

•ovarian tumors are uncommon in cats and dogs

•ovarian tumors account for 0.7%-3.6% of all tumors in cats and 0.5%-1.2% of tumors in dogs

•ovarian tumors are more common in older nulliparous bitches

•granulosa-theca cell tumor and Sertoli-Leydig cell tumor are the most common ovarian tumors

EPITHELIAL OVARIAN TUMORS

General Considerations

•epithelial tumors account for 40%-50% of all ovarian tumors in dogs, but are very rare in cats

•breed predisposition: Pointers

•types: papillary adenoma, papillary ADC, cystadenoma, and undifferentiated carcinoma

•metastasis of LSA and endometrial ADC to the ovaries has been reported in cats

Papillary Adenoma and Adenocarcinoma

•papillary adenoma and ADC can be bilateral

•differentiation between papillary adenoma and ADC is difficult and based on size, mitotic index, invasion into ovarian stroma, and extension into ovarian bursa and adjacent peritoneum

•papillary ADC associated with widespread peritoneal implantation and malignant effusion

•malignant effusion develops due to:

•edema within the ovarian tumor resulting in fluid leakage the through tumor capsule

•exfoliation and implantation of tumor cells resulting in occlusion of peritoneal and diaphragmatic lymphatics

•secretions from metastatic peritoneal implants

•50% metastatic rate with metastasis to the renal and para-aortic lymph nodes, omentum, liver, and lungs

Cystadenoma

•cystadenoma originates from rete ovarii

•unilateral

•multiple thin-walled cysts containing clear serous fluid

Undifferentiated Carcinoma

•embryonal morphology and absence of hormonal secretion

•50% metastatic rate

GERM CELL TUMORS

General Considerations

•germ cell tumors account for 6%-20% of all canine ovarian tumors

•types: dysgerminoma, teratocarcinoma, and teratoma

Dysgerminoma

•dysgerminoma arise from undifferentiated germ cells and consist of a uniform population of cells resembling primordial ovarian germ cells

•dysgerminoma resembles testicular seminoma in male dogs and have been termed ovarian seminoma

•dysgerminoma represents 15% of all feline ovarian tumors

•dysgerminomas are usually unilateral, but bilateral tumors have been reported (especially in cats)

•dysgerminoma grow by expansion rather than invasion

•10%-30% metastatic rate with metastatic sites including abdominal lymph nodes (common), liver, kidney, omentum, pancreas, adrenal glands, and brain

Teratoma

•teratomas are more common in bitches < 6 years

•teratoma is composed of ≥ 2 germinal cell layers with any combination of ectodermal, mesodermal, and endodermal tissue

•teratomas are usually well-differentiated

Teratocarcinoma

•teratocarcinomas consists of mature and undifferentiated elements

•32%-50% metastatic rate with metastasis to multiple abdominal sites, lungs, cranial mediastinum, and bone

•metastatic lesions composed primarily of undifferentiated tissue

SEX-CORD STROMAL TUMORS

General Considerations

•sex-cord stromal tumors account for 34%-50% of ovarian tumors in cats and dogs

•types: granulosa cell tumor (common), thecoma, and luteoma

•sex-cord stromal tumors are unilateral although Sertoli-Leydig cell tumors are bilateral in 36% dogs

•sex-cord stromal tumors are functional tumors as they arise from specialized gonadal stroma of the ovary which is responsible for the production of estrogen and progesterone

Granulosa Cell Tumor

•breed predisposition: English Bulldog

•gross appearance: firm and lobulated

•Call-Exener body formation is diagnostic with gland-like or rosette patterns of abortive follicle formation often containing a central secretory globule which resembles an ovum

•> 50% metastatic rate in cats with metastasis to the peritoneum, sublumbar lymph nodes, omentum, diaphragm, kidney, spleen, liver, and lungs

•20% metastatic rate in dogs with metastasis to the sublumbar lymph nodes, liver, pancreas, lung, and peritoneal carcinomatosis

Thecoma and Luteoma

•thecomas and luteomas are rare

•luteoma occurs more commonly in cats than dogs

•thecoma is histologically similar to FSA and differentiated from FSA due to presence of lipid droplets

•thecomas are benign with expansile growth rather than invasion

•thecomas can be functional with production of estrogen more common than testosterone

Tumor-Like Conditions

•ovarian cysts can be very large

•paraovarian cysts arise from mesonephric ducts and can either be single or multiple

•other: cystic rete tubules, vascular hematoma, and adenomatous hyperplasia of rete ovarii

CLINICAL FEATURES

Clinical Signs

•young dogs commonly affected with teratomas and middle-aged to older animals with other ovarian tumors

•space-occupying mass is the most common sign

•epithelial tumors can produce malignant effusion with characteristic signet ring and rosette cellular pattern

•sex-cord stromal tumors are functional:

•excessive estrogen production results in vulvar enlargement, hyperplasia and cornification of vaginal epithelium, sanguineous vulvar discharge, persistent estrous, alopecia, and aplastic pancytopenia

•excessive progesterone production results in cystic endometrial hyperplasia and pyometra

•thecomas are associated with feminizing effects and luteoma with masculinizing effects, but both are rare

•dysgerminoma in cats associated with depression, vomiting, abdominal distension, and ascites

Diagnosis

•abdominal mass ± clinical signs referable to the reproductive tract

•survey radiographs: calcification with teratoma

•excretory urography can be used to differentiated renal and ovarian tumors

•thoracic radiographs for metastatic disease but rarely positive at the time of diagnosis

•benign lesions usually appear cystic with well-defined margins on abdominal ultrasonographic examination, whereas malignancy is more likely when ovarian masses have a proportion of the mass appearing solid

•aspiration is not recommended due to propensity for exfoliation and implantation on peritoneal surface

•histopathology

TREATMENT

Medical Management

•intracavitary cisplatin for management of malignant effusion

•platinum drugs with tamoxifen used in metastatic human ovarian tumors

•hectate-b significantly decreases tumor burden

Surgical Management

•ovariohysterectomy or ovariectomy

•gentle handling is required to minimize tumor exfoliation and peritoneal seeding

Prognosis

•prognosis is good if single tumor with complete excision and no evidence of metastatic disease