A 34-year-old woman from Guinea with no medical history was diagnosed in 2007 with acute adult T-cell leukemia/lymphoma (ATL/L) when she was seen with fatigue, lymphocytosis with cerebriform cells, and multiple osteolytic lesions. Immunologic typing showed that these cells strongly expressed CD3, CD4, and CD25. Human T-cell lymphotropic virus type 1 (HTLV-1) serologic test results were positive by enzyme-linked immunosorbent assay and Western blot analysis. Thoracoabdominopelvic computed tomography and bone marrow biopsy specimens revealed no abnormalities. Six cycles of CHOP chemotherapy (cyclophosphamide, doxorubicin, vincristine, and prednisone) with bortezomib resulted in partial response.