Mediastinal T-cell lymphoma in a free-ranging brown howler monkey (Alouatta guariba clamitans).

A free-ranging brown howler monkey (Atelidae: Alouatta guariba clamitans) was necropsied and a mediastinal T-cell lymphoma and esophageal dilation were diagnosed. The case report may contribute to the differential diagnosis of neoplastic and esophageal lesions in non-human primates and highlighted the importance of surveillance of cancer in wildlife.