Diffuse large B-cell lymphoma affecting the third eyelid of two young adult FeLV-infected cats.

Lymphoma is one of the most frequently diagnosed tumors in FeLV-infected cats. Extranodal lymphomas include lymphomas in ocular and periocular tissues, such as the third eyelid (TEL), which is an uncommonly diagnosed type of lymphoma in cats. This study aimed to describe the clinicopathological features of lymphoma in the TEL of two FeLV-infected cats. A retrospective study in two anatomic pathology laboratories was performed, and two cases met the inclusion criteria. A 4-year-old, female cat (case 1), positive for FIV gp40 antigen and FeLV gp70 antigen by immunohistochemistry (IHC), and a male cat of 22 months old (case 2), positive both serologically for FeLV p27 antigen and for FeLV gp70 antigen by IHC, were referred to veterinary clinics with unilateral swelling and mass in the TEL, which had rapid growth in case 2. Histological and immunohistochemical analysis established the final diagnosis of diffuse large B-cell lymphoma in both cases. The cat in case 2 died 4 months after the diagnosis, with clinical worsening prior to death. Necropsy was not performed in either case, which precluded the definition of a primary or secondary involvement. However, the ocular lesions were the reason for consultation in both cases and it may have been an initial manifestation of a multicentric disease. Thus, FeLV-infected cats with clinical finding of eyelid swelling or mass formation should have lymphoma as a differential diagnosis, and a complete physical examination should be performed to detect extraocular involvement.