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Lymphoma is one of the most common tumours of domestic cats. Microscopically, it can be challenging to distinguish lymphoma (monoclonal lymphoid proliferation) from reactive lymphoid hyperplasia (polyclonal lymphoid proliferation). Molecular methods that characterize cellular clonality can overcome this diagnostic challenge; however, it is essential to know which variable and joining region variants are utilized by neoplastic lymphocytes before a sensitive and specific assay can be developed. The present study describes a polymerase chain reaction assay that allows for complete sequencing of clonally recombined T-cell receptor (TCR) γ chain genes from formalin-fixed and paraffin wax-embedded samples of feline lymphoma. The variable (V) and joining (J) region variants of the TCR γ chain were characterized in 50 feline lymphomas. Amplification and sequencing with primers directed against conserved framework regions 1, 2 and 4 of the TCR γ chain identified clonal rearrangement in 68% of T-cell lymphomas and 22% of B-cell lymphomas. The distribution of TCR variants present in B- and T-cell lymphomas was similar and included V region variants 1 and 3, and J region variants 1.2, 1.3 and 1.5. V region variants 2 and 4 were not identified in either tumour type. Some feline B-cell lymphomas had a clonally rearranged TCR, a finding reported in human, but not canine, B-cell lymphoma.