Ovarian Tumors

+ 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
• More common in older nulliparous bitches
• Granulosa-theca cell tumor and Sertoli-Leydig cell tumor are the most common 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

+ 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

+ 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 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

+ 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
• Survival time of up to 4 years for dysgerminoma and 6 years for teratoma have been reported
• Chemotherapy has the potential to prolong life in animals with metastatic ovarian tumors