October 2017



Signalment (JPC #2055944): Sheep, breed not specified

HISTORY: Exhibited respiratory distress.

HISTOPATHOLOGIC DESCRIPTION: Lung: Multifocally arising from the alveolar epithelium, replacing 60% of normal pulmonary architecture and compressing adjacent alveoli (atelectasis) are variably-sized, up to 1mm diameter, unencapsulated, well-demarcated, expansile neoplastic foci composed of one or more layers of cuboidal to columnar epithelial cells which form acinar or papillary projections into alveolar lumina and are supported by a fine fibrovascular stroma. Neoplastic cells have distinct cell borders, a moderate amount of finely granular, occasionally vacuolated amphophilic to lightly eosinophilic cytoplasm, and round to oval nuclei with finely-stippled chromatin, and 1‑3 variably distinct nucleoli. The mitotic rate is less than 1 per 10 HPF. Multifocally, alveolar and bronchiolar lumina contain variable numbers of degenerate and nondegenerate neutrophils, foamy alveolar macrophages, fibrin, and edema. Multifocally, alveolar septa are mildly expanded by the previously-described inflammatory cells.  Bronchiolar epithelium is frequently hyperplastic, piling up to 6 layers thick, and contains moderate numbers of goblet cells (goblet cell metaplasia). The pleura and interlobular septa are expanded up to 5 times normal by increased clear space and ectatic lymphatics (edema) and scattered previously-described inflammatory cells.  Multifocally, there are increased numbers of bronchiole-associated lymphocytes, which occasionally form germinal centers (BALT hyperplasia).

MORPHOLOGIC DIAGNOSIS: Lung:  Pulmonary adenocarcinoma, low-grade, breed unspecified, ovine

ETIOLOGIC DIAGNOSIS: Retroviral pulmonary carcinomatosis

CAUSE: Betaretrovirus (Jaagsiekte sheep retrovirus [JSRV])

CONDITION: Ovine pulmonary adenocarcinoma (OPA)

SYNONYMS: Jaagsiekte, ovine pulmonary carcinoma, pulmonary adenomatosis











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