Identification of Atypic and Classic, Mucinous and Nonmucinous Forms of Ovine Pulmonary Adenocarcinoma (OPA) and TTF1 Marker Expression

BACKGROUND: Ovine pulmonary adenocarcinoma (OPA) is a worldwide contagious bronchioalveolar carcinoma caused by infection of a beta retrovirus in sheep and less in goat. Neoplastic proliferation of type II pneumocytes and clara cells, produce papillary to acinar tumoral pattern with infiltration of macrophages, lymphocytes and plasma cells and interstitial fibrosis tissue. OBJECTIVES: This study was conducted to investigate the patterns of OPA and check the expression of TTF1. METHODS: A total of 7952 ovine lungs were studied for macroscopic and microscopic pathology examination and so, to check TTF1 marker. RESULTS: 25 cases were diagnosed as OPA and, based on macroscopic and histopathologic lesions, two different classifications were defined. Tumoral lesions were divided to classic (68%) and atypic (32%) forms of OPA based on growth pattern and progression and two other forms of mucinous (56%) and non-mucinous (44%) OPA based on histologic characterization of neoplastic secretory cells were descripted. 6 out of 8 examined cases for TTF1 marker staining, were positive and 2 cases were negative in immunohistochemical test. CONCLUSIONS: Two forms of classic and atypic lesions and so mucinous and non-mucinous forms were found. The classic form was more than the atypic and the mucinous form was more than non-mucinous lesions. TTF1 marker expression revealed the pulmonary origin of tumors.