JPC SYSTEMIC PATHOLOGY
REPRODUCTIVE SYSTEM
January 2022
R-N06
Signalment (JPC #4143285): 8-year-old female, now spayed, Boston terrier.
HISTORY: At routine ovariohysterectomy, the surgeon noted an enlarged, irregular right ovary.
HISTOPATHOLOGIC DESCRIPTION: Ovary: Diffusely replacing normal architecture and entrapping or compressing rare remaining ovarian follicles is a poorly circumscribed, unencapsulated, densely cellular neoplasm composed of round cells arranged in sheets and occasional cords which are separated by scant fibrous connective tissue stroma. Neoplastic cells have distinct cell borders and a small to moderate amount of eosinophilic, granular to vacuolated cytoplasm. Nuclei are large, centrally placed, irregularly round, and have vesiculate to coarse chromatin with 1-3 prominent magenta nucleoli. There is marked anisokaryosis and anisocytosis, and mitoses average 30 per 2.37 sq mm. Neoplastic cells are occasionally multinucleated or contain large pleomorphic nuclei and there is scattered individual cell necrosis.
MORPHOLOGIC DIAGNOSIS: Ovary (per contributor): Dysgerminoma, Boston terrier, canine.
GENERAL DISCUSSION:
- Tumors of primordial germ cells of the embryonic gonad
- Female counterpart of testicular seminoma in males
- All considered malignant, though metastases are rare
- Rare in most species; most common in the dog but reported in queen, cow, mare, and sow as well; most occur in aged animals
PATHOGENESIS:
- Arise from ovarian germ cells, often have seminoma-like characteristics
TYPICAL CLINICAL FINDINGS:
- Clinical signs are variable and may be absent or nonspecific
- Small percentage may be hormonally active inducing hyperestrogenism
- Fever, pyometra or vaginal discharge, vomiting and diarrhea reported in bitches
TYPICAL GROSS FINDINGS:
- Usually unilateral; may be bilateral
- May be large, especially in cows (up to 46 cm and 14 kg)
- Variable size; round to oval with a smooth to lobulated surface
- Gray-white; soft, and/or cystic; often foci of hemorrhage and/or necrosis
TYPICAL LIGHT MICROSCOPIC FINDINGS:
- Composed of uniform round to polygonal cells arranged in sheets or cords with thin strands of connective tissue
- Diffuse growth pattern; scant stroma is a consistent feature
- Vesicular to amphophilic cytoplasm
- Round to oval nuclei with coarsely granular chromatin
- Multinucleated giant cells occasional or frequent
- High mitotic rate
- Individual cell necrosis and cystic degeneration may occur
- Often have accumulations of lymphocytes
ADDITIONAL DIAGNOSTICS:
- Immunohistochemistry:
- Sal-like protein 4 (SALL4): Most likely to be immunopositive; may exhibit nuclear with or without cytoplasmic immunoreactivity
- PLAP & OCT3/4: May express cytoplasmic immunoreactivity
- c-kit: Typically immunonegative
DIFFERENTIAL DIAGNOSIS:
- Lymphoma
- Granulosa cell tumor (R-N05): Polycystic tumor with cells arranged in nests and cords; Call-Exner bodies in some cases
- Papillary cystadenoma/cystadenocarcinoma: Fibrovascular tumor with secretory cells and cystic structures
- Theca cell tumor: Fusiform neoplastic cells, often with cytoplasmic lipid
- Interstitial cell tumor: Polyhedral cells with distinct cell borders and cytoplasmic lipid droplets
- Teratoma (R-N08): Composed of multiple tissues from two or more germ lines
COMPARATIVE PATHOLOGY:
- Occur with relatively high frequency in maned wolves
- Can cause hypercalcemia that stems from abnormal synthesis of the active form of vitamin D, 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) from tumor-associated macrophages and inflammatory cells
REFERENCES:
- Agnew DW, MacLachlan NJ. Tumors of the genital systems. In: Meuten, DJ, ed. Tumors in Domestic Animals. 5th ed. Ames, IA: John Wiley & Sons, Inc.; 2017:698.
- Foster RA. Female reproductive system and mammae. In: Zachary JF, ed. Pathologic Basis of Veterinary Disease. 6th ed. St. Louis, MO: Elsevier; 2017:1161.
- Keel MK, Terio KA, McAloose D. Canidae, Ursidae, and Ailuridae. In: Terio KA, McAloose D, St. Leger J ed. Pathology of Wildlife and Zoo Animals. Cambridge, MA: Elsevier Inc. 2018:239.
- Rosa RB, Bianchi MV, Ribeiro PR. Comparison of immunohistochemical profiles of ovarian germ cells in dysgerminomas of a captive maned wolf and domestic dogs. J Vet Diagn Invest. 2021;33(4):772-776.
- Schlafer DH, Foster RA. Female genital system. In: Maxie MG, ed. Jubb, Kennedy, and Palmer’s Pathology of Domestic Animals. Vol 3. 6th ed. St. Louis, MO: Elsevier; 2016:377-378.
