[Long-term remission with mogamulizumab monotherapy in a patient with refractory adult T-cell leukemia-lymphoma].

A 73-year-old female with malaise, anorexia, and hydrodipsia was referred to our department. Peripheral blood tests revealed leukocytosis with 51% blast cells exhibiting flower-shaped nuclei. Flow-cytometry to detect tumor cells in peripheral blood indicated CD3+, CD4+, CD8-, and CD25- expression, but those in the lymph nodes expressed CD25+. Southern blots revealed clonal HTLV-1 provirus in the tumor cells, consistent with adult T-cell leukemia-lymphoma. Cytotoxic chemotherapy was ineffective, but eight cycles of mogamulizumab induced complete remission (CR). A relapse lesion appeared on the right breast but disappeared spontaneously. The patient has currently maintained CR for over five years.