Morphopathological study of naturally occurring ovine pulmonary adenocarcinoma in sheep in Fars province, Iran.

Abstract

Summary Ovine pulmonary adenocarcinoma (OPA) is a contagious and transmissible lung cancer of sheep resembling human bronchiolo-alveolar carcinoma. In the present study, lungs of 9400 sheep slaughtered in Fars province, Iran were examined morphopathologically. The OPA was diagnosed in the lungs of 21 (0.22%) out of 9400 sheep. Frequency of involvement of different lobes in the affected lungs was inclu ded apical lobe (62%), cardiac lobe (33%), middle lobe (33%), diaphragmatic lobe (62%) and accessory lobe (5%). In 12 sheep, the classical form observed as f irm, white to grayish coalescing masses mostly in t he cranio-ventral lobes associated with wet cut surfac e and frothy fluid in the airways. In 9 sheep, atyp ical lesions observed as small clearly demarcated nodule s mostly in diaphragmatic lobes associated with dry cut surface and minor fluid in the airways. Histopathol ogical changes were almost similar in the two forms . They consisted of an acinar or papillary growth of neopl astic cells in the alveoli and polypoid proliferati on of bronchiolar epithelium. There were variable amounts of connective tissue, myxomatous foci and infiltra tion of lymphocytes and plasma cells in the interstitial tissue of the affected alveoli. No metastatic lesi on was observed in the lymph nodes. The findings of this s tudy show that atypical and classical forms represe nt different stages or manifestations of a single dise ase spectrum.