First cancer in an extinct Quaternary non-human mammal

Here we report a parosteal osteosarcoma, a malignant bone neoplasm, in a right femur assigned to the Quaternary ground sloth <i>Nothrotherium maquinense</i>. The specimen was collected at Lapa dos Peixes I, a cave located at Serra do Ramalho plateau, Bahia, Brazil. The diagnosis was based on the macroscopic, radiologic and histologic appearance of the lesion. The presence of this pathology may indicate that the individual suffered from local pain, localised swelling and limitation of joint movement, which would have been extremely harmful for its life. Even though neoplasms are recognised in almost all metazoans, this is the first case of cancer reported for a Quaternary non-human mammal and appears to be the first report of this specific form of bone cancer in the fossil record.