A poorly differentiated pulmonary squamous cell carcinoma in a free-ranging Atlantic bottlenose dolphin (Tursiops truncatus).

A free-ranging, adult, female offshore bottlenose dolphin (Tursiops truncatus) was found freshly dead in 1999 on Ocean Park Beach in San Juan, Puerto Rico. The left-lung and right-lung pleura had multiple white, firm-to-hard nodules with coagulative necrosis. Histologically, the neoplasms were characterized by multiple well-circumscribed, nonencapsulated expansile masses consisting mostly of polygonal cells with fewer circumferential flattened basaloid cells that compressed alveoli, bronchioles, and bronchi. Neoplastic cells stained positive for cytokeratin, with sporadic vimentin staining, and were negative for epithelial membrane antigen, thyroid transcription factor-1, calretinin, and human mesothelial cell antigen. A diagnosis of poorly differentiated pulmonary squamous cell carcinoma with lymph node and renal metastases was made on the basis of histomorphology and immunohistochemical staining. This is the first documentation of pulmonary squamous cell carcinoma in a dolphin.