The giant anteater (Myrmecophaga tridactyla) is a typical neotropical mammal, and in spite of being maintained in captivity in zoos in South America and other parts of the world, captive populations are small, and medical knowledge of the species is scarce.
This paper reports a case of disseminated lymphosarcoma in an adult male giant anteater from the City Zoo of Curitiba, State of Parana, Brazil. The animal came from the wild as an adult and lived in the zoo for 3 years.
No clinical signs were noticed prior to death, except for slight inappetence. The animal was necropsied immediately after death, and pale yellow or white masses of various sizes were found in the heart, liver, and lymph nodes. The most significant gross lesion was found in the heart. Samples of the affected tissues were collected and preserved in a 10% formalin solution. After fixation, the tissues were routinely processed for microscopic examination using hematoxylin plus eosin.
In the heart, the histologic examination revealed multifocal areas of neoplastic cells, with a high nucleus/cytoplasm ratio and evident nucleoli, gross nuclear chromatin, and one to three mitotic figures in each microscopic field. The cells were infiltrated between the cardiac muscle fibers, without the presence of a fibrous capsule. Proliferation of two lymphoid cell populations was identified, with moderate pleomorphism between them—histiocytic and lymphoblastic. The same kind of neoplastic tissue was present in samples of liver and lymph nodes.
Disseminated lymphosarcomas are well documented in domestic animals, but this is the first Brazilian report in a giant anteater (Myrmecophaga tridactyla).