+ 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