Fig. 1

Gross features of spontaneous OPA in sheep. a Distribution of pulmonary lesions; b Classical form of OPA, involving the diaphragmatic lobe (arrow); c Classical form of OPA, affecting multiple pulmonary lobes (arrows); d Classical form of OPA on cut surface showing the junction (interrupted line) between the tumor and normal tissue; e and e1 Atypical form of OPA showing a subpleural white-grey nodule (arrow). On cut surface, the tumor is pearly white and dried (arrow); f Gross aspects of pulmonary myxoma-like nodule (arrow); g the myxomatous mass shows a multilobular, white-gray, gelatinous feature on cut surface