Metastatic primary lung tumor in three dogs

Primary lung tumors (PLT) are uncommon in dogs and occasionally metastasize to distant organs. This report describes three cases of PLT in dogs with epithelial origin, diagnosed post mortem through histopathology and immunohistochemistry. Case one presented nonspecific symptoms while the second and third cases presented respiratory alterations and radiographic exams revealed the presence of pulmonary nodule(s). Case 1 was diagnosed as a pulmonary papillary adenocarcinoma with metastasis to the mediastinal lymph nodes, liver and right adrenal gland. Case 2 was a pulmonary squamous cell carcinoma with metastasis to the heart, kidneys and perianal gland, whereas Case 3 was diagnosed as pulmonary papillary adenocarcinoma with metastasis to the pericardium and mediastinal lymph nodes. There is no previous report of epithelial TPP metastasis to pericardium, heart, liver, kidney and perianal gland. The three tumors showed positive immunostaining for the anti-pan-cytokeratin antibody and negative immunostaining for the anti-vimentin antibody. In dogs with PLT, the TNM clinical staging and histological classification and grading are fundamental for therapeutic planning and prognosis determination.