JPC SYSTEMIC PATHOLOGY
Signalment (08-12024): 10-year-old, intact male, Labrador retriever, canine.
HISTORY: A 10-year-old intact male Labrador retriever was diagnosed with a thoracic mass. The dog had a history of mild chronic cough, hematuria, acute right eye pain and lethargy. Physical examination revealed blepharospasm and hyphema with clear discharge from the right eye, a firm mass in an enlarged right testicle and an enlarged irregular prostate. An ultrasonographic examination revealed nodules in the prostate, liver, spleen, and left kidney. The dog was euthanized a week later due to rapid deterioration with anorexia, acute blindness and ataxia.
HISTOPATHOLOGIC DESCRIPTION: 1. Lung: Effacing and compressing approximately 80% of this section of lung and infiltrating into adjacent alveolar septa is an unencapsulated, poorly circumscribed, multinodular, densely cellular neoplasm composed of anaplastic epitheloid to slightly spindle-shaped cells arranged in vague nests, streams, solidly cellular sheets, and forming variably sized vascular channels that are separated and supported by a fibrovascular matrix. Neoplastic cells have distinct cell borders, an abundant amount of eosinophilic to vacuolated cytoplasm that rarely contains a single erythrocyte, a round to pleomorphic vesiculate nucleus that often bulges into vascular lumens with coarsely clumped chromatin, and 1-3 prominent nucleoli. Anisocytosis and anisokaryosis are marked. Mitotic count averages 3-5 per high powered field with frequent bizarre mitoses present. Multifocally, there are solid large nests of neoplastic cells which penetrate and occlude pulmonary vessels. Predominantly within the central areas of the neoplasm there are occasional fibrin thrombi, moderate hemorrhage, scattered single cell necrosis, viable and degenerate neutrophils, hemosiderin-laden macrophages, and scattered aggregates of lymphocytes and plasma cells admixed with necrotic cellular debris.
Prostate, liver, kidney: Previously described neoplastic cells, hemorrhage, inflammation, and necrosis infiltrate and efface the small sections of prostate, liver, and kidney.
2. Prostate: Diffusely there is hyperplasia of the glandular epithelium with multifocal variably sized dilations of the alveoli (cystic change) that contain a pale homogenous eosinophilic secretory product and sloughed epithelial cells. Cysts are lined by simple cuboidal to columnar epithelium. Multifocally within the stroma there is a mild infiltration by lymphocytes and plasma cells.
MORPHOLOGIC DIAGNOSES: 1. Lung, prostate, liver, kidney: Metastatic epithelioid hemangiosarcoma, Labrador retriever, canine.
- Prostate: Hyperplasia, glandular epithelial with numerous cysts, diffuse, mild.
- Epithelioid hemangiosarcoma is a rarely reported histologic variant of hemangiosarcoma, a malignant neoplasm of vascular endothelial origin
- Poses a diagnostic challenge due to the epithelial-like morphology of neoplastic cells
- Most cases occur in the integument, but there have been reports of disseminated visceral disease without evidence of cutaneous involvement
- May be solar induced in dogs and horses, particularly in glaborous skin or sparsely haired areas
TYPICAL GROSS FINDINGS:
- Single or multiple well-defined mass; red/brown to black; soft to firm; exudes blood when incised
- Masses can be present in multiple organs in disseminated disease
- When involving the skin there is often alopecia, thickened skin, hemorrhage, or ulceration
TYPICAL LIGHT MICROSCOPIC FINDINGS:
- Pleomorphic, epithelioid to spindle cells forming a papillary projections or vague blood filled vascular spaces
- There may be little to no histologic evidence of vascular origin
- Neoplastic cells have abundant, eosinophilic, granular or vesicular cytoplasm that occasionally contains a single erythrocyte
- Nuclei are vesicular, with one or more prominent nucleoli
- Mitotic count is highly variable
- Large pleomorphic endothelial cells with a prominent basal lamina
- Neoplastic cells rarely contain Weibel-Palade bodies (Specific cytoplasmic marker for endothelial cells)
ADDITIONAL DIAGNOSTIC TESTS:
- Immunohistochemistry: Neoplastic cells are immunopositive for vimentin and at least one of the commonly used vascular markers (Factor VIII-related antigen (vWF), CD31(PECAM), and CD34).
- Neoplastic cells will negative for cytokeratin (AE1/AE3)
- Epithelioid vascular neoplasms are characterized by peculiar epithelioid or histiocytic appearance of the endothelial cells; need to rule out anaplastic carcinoma and histiocytic sarcoma
- Immunohistochemistry for vascular endothelium required for definitive diagnosis
- Horses: Reported in the perioccular tissue and vulva; may be associated with solar elastosis secondary to UV radiation
- Bovine: Reported in the skin, urinary bladder, regional lymph nodes, lung, kidney, and liver
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