Angioinvasive lymphoma (lymphomatoid granulomatosis) in a cat, with cutaneous and ocular metastasis

Lymphomatoid granulomatosis (LYG) is a rare variant of an angioinvasive T-cell lymphoproliferative disorder that primarily affects the lungs, with common sites of metastasis including the skin and subcutis. In humans, it is a B-cell lymphoproliferative disorder associated with Epstein-Barr virus infection. Our case is a 7-y-old, spayed female, domestic longhair cat that decompensated and was euthanized following an initial diagnosis of angioinvasive lymphoma from a skin biopsy. Autopsy revealed nodules in the lungs and subcutis, and corneal thickening and cloudiness. Histologic examination of cutaneous nodules, lungs, and eye showed similar angioinvasive cellular infiltrates and pattern to that of the original skin biopsy, consistent with a diagnosis of LYG. The neoplastic cells displayed CD3-positive immunoreactivity in the skin, eye, and lung, and PCR for antigen receptor rearrangement (PARR) showed T-cell clonality in all tissues tested. This is the third case of LYG to be reported in cats and is the only case in which PARR analysis and immunophenotyping immunohistochemical staining was performed. LYG with ocular involvement has not been reported previously in cats, to our knowledge. Our case demonstrates the necessity for considering LYG when presented with a cat with respiratory signs in conjunction with subcutaneous nodules and ocular lesions.