Abstract
T‐cell prolymphocytic leukemia (T‐PLL) is a rare, mature T‐cell leukemia which usually presents with aggressive behavior. We report an asymptomatic T‐PLL patient diagnosed by clinical features, lymphocyte morphology, and flow cytometry. Incidentally, she was found to have lymphocytosis and lymphadenopathy. Flow cytometry from blood revealed an abnormally increased CD4+ T‐cell population. T‐cell receptor clonality assessment by next‐generation sequencing revealed a dominant clone in the ß‐chain constant region. No pathogenic mutations in 25 lymphoma‐related genes were found. Due to her asymptomatic T‐PLL disease, we observed her clinical situation and blood count every three months for at least one year.