Abstract: Intravascular lymphoma of T and NK cell origin is extremely rare, herein, we report a case. A 76-year-old male presented with intermittent fever for more than one month, and erythema on both thighs for half a month. Pathological examination of skin lesions showed large and atypical mononuclear cells of varying numbers were found in small blood vessels in the dermis and fat. Immunohistochemistry showed positive EBER in situ hybridization, CD3(+), CD4(+), CD8(+), CD56(+), TIA-1(+), Gr-B(+), Perforin(+), Ki-67(60%+). The diagnosis of intravascular NK/T cell lymphoma was made. After 4 courses of P-Gemox treatment, the patient was given chidamide and sintilimab. The rash on both thighs almost disappeared, and there was no tumor progression during the 6-month follow-up.

Key words: intravascular NK/T cell lymphoma, skin manifestations, immunohistochemistry