A case of T-prolymphocytic leukemia harboring RAS mutation.

The text reports the clinical case of a 61-year-old woman with a long history of generalized pruritus who was eventually diagnosed with T-cell prolymphocytic leukemia (T-PLL), a rare and aggressive T-cell lymphoproliferative disorder. At presentation, the patient had fever, skin lesions, lymphocytosis, thrombocytopenia, coagulation abnormalities, and marked splenomegaly without lymphadenopathy. Morphological, immunophenotypic, and histological analyses of peripheral blood and bone marrow revealed diffuse infiltration by mature T lymphocytes with strong TCL1 expression, and T-cell receptor gene rearrangement confirmed clonality, supporting the diagnosis of T-PLL. The patient initially received bendamustine chemotherapy, which failed to induce a response. Second-line treatment with the anti-CD52 monoclonal antibody alemtuzumab was subsequently initiated, but the disease proved refractory, with persistent bone marrow involvement, worsening cytopenias, disease progression, and clinical deterioration. As a result, alemtuzumab was discontinued and the patient was transitioned to palliative care. A particularly notable finding was the detection, by next-generation sequencing, of a pathogenic KRAS G12A mutation, which has not previously been reported in T-PLL. This mutation was identified incidentally using a myeloid-targeted NGS panel. The finding broadens the known mutational spectrum of T-PLL and suggests that activation of the RAS signaling pathway may represent an alternative oncogenic mechanism beyond the canonical TCL1 and JAK–STAT pathways. We suggest that investigating for KRAS mutations in additional T-PLL cases may be beneficial to explore this pathogenetic pathway and could open new avenues for future targeted therapeutic strategies.