Feline intestinal T-cell lymphoma: assessment of morphologic and kinetic features in 30 cases

In this study, 30 feline intestinal T-cell lymphomas (ITCLs) from 77 cats with gastrointestinal lymphoma were evaluated. Neoplastic lesions were composed predominantly of small (n = 21) or medium to large (n = 9) anaplastic cells. Different patterns of tumor growth were observed. A starry-sky pattern was evident in 7 cases (23.3%), fibrosis in 18 cases (60%), and neovascularization in 19 cases (63.3%). The cell proliferation index (assessed by MIB1 [mindbomb homolog 1] immunohistochemistry) ranged from 0.21% to 66.91%. Mean MIB1 index was 3.49% within the first 33rd percentile, 18.31% within the second 33rd percentile, and 40.16% within the third 33rd percentile (P < 0.000001). Microscopic and kinetic features provided evidence that ITCL in cats exhibits a spectrum in cytological composition and growth patterns that could putatively reflect differences in biologic behavior.