Tonsillar T-cell lymphoma with hepatic and renal metastases in a fattening domestic pig (Sus scrofa domesticus).

[BACKGROUND] In pigs, lymphoma is documented only sporadically in literature. Compared with other livestock species, such as cattle, lymphoma in pigs has a significantly lower incidence. The low number of reported cases may be due in part to underdiagnosis related to the production environment in which these animals are raised, together with the sporadic and non–virus-associated nature of the disease. Although rare, lymphomas represent the most frequent form of hematopoietic tumor in this species with different sites of development. To date, there are no clear reports of primary tonsillar lymphoma in pigs in the literature.

[CASE PRESENTATION] This case report describes a rare case of tonsillar lymphoma with liver and kidney metastases in an intensively reared male castrated Danish pig. The animal, apparently in good health, was found dead at the age of 4 months (120 days), without any premonitory clinical signs. On necropsy, enlargement of the tonsils of the soft palate, with firm consistency and red color and multiple white-to-gray nodules in the liver and kidneys were observed, and considered consistent with a round cell tumor. Histopathological and immunohistochemical analyses identified a T cell lymphoma with primary tonsillar localization and metastatic spread.

[CONCLUSIONS] Compared with other livestock species, such as cattle, lymphoma in pigs has a significantly lower incidence and this report contributes to expanding knowledge about the anatomical distribution and biological behavior of lymphomas in pigs. This case highlights the importance of including histologic examination of the tonsils in postmortem investigations, especially in the presence of metastatic lesions of uncertain origin. It also suggests the usefulness of implementing systematic reporting systems for neoplastic lesions in pigs to improve health surveillance and deepen the epidemiology of neoplasms in the swine species. Increased awareness among farm veterinarians, inspectors, and diagnosticians can help refine early diagnosis and health management on the farm.