JPC SYSTEMIC PATHOLOGY
Signalment (JPC #2329087): 9-year-old maned wolf (Chrysocyon brachyurus).
HISTORY: Abdominal mass
HISTOPATHOLOGIC DESCRIPTION: Ovary (per contributor): 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 a scant fibrous connective tissue stroma. Neoplastic cells have distinct cell borders and small to moderate amounts of eosinophilic granular to vacuolated cytoplasm. Nuclei are large, centrally placed, irregularly round, and vesiculate with 1-2 prominent magenta nucleoli. There is moderate anisokaryosis and anisocytosis, and mitoses average 3 per HPF. Neoplastic cells are occasionally multinucleated or contain large pleomorphic nuclei. There is multifocal individual cell necrosis, scattered hemorrhage and rare cystic areas filled with homogenous eosinophilic proteinaceous fluid. Focally the neoplastic cells extend through the tunica albuginea into the surrounding adipose tissue.
MORPHOLOGIC DIAGNOSIS: Ovary (per contributor): Dysgerminoma, maned wolf (Chrysocyon brachyurus), canine.
- 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
- 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
- IHC POSITIVE for protein gene product 9.5 (5) and Sal-like protein 4(Sall4)
- IHC NEGATIVE for c-Kit (human dysgerminomas are c-Kit positive), placental alkaline phosphatase (PLAP), and do not stain with PAS
- Granulosa-cell tumor: 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: Composed of multiple tissues from two or more germ lines
- Reported in genetically related women and in related maned wolves (4 cases)
- Reported rarely in cats, cows, horses, pigs, goats, fish, soft-shelled clams (linked to herbicides), snapping turtle (1 case), rhesus monkey (1 case), dusky dolphin (1 highly suggestive case), mountain chicken frogs (1 case), Eastern Rosella (1 case, psittaciform bird)
- In humans, dysgerminoma accounts for 2% of ovarian cancers; these may be associated with gonadal dysgenesis, including pseudohermaphroditism, or teratomas
- 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
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