Isolated relapse of acute lymphoblastic leukemia in the breast of a young female

A 20-year-old female developed a relapse of B-precursor acute lymphoblastic leukemia (ALL) as a mass in her left breast after 6 years of maintained continuous complete remission. No leukemic lesions were identified in other sites such as the bone marrow or cerebrospinal fluid. The relapsed leukemic cells in the breast revealed the same immunophenotypes (CD10(+), CD19(+), CD20(+), HLA-DR(+), CD34(+)) as those of the onset ALL cells in the bone marrow. A literature survey found 10 other cases of ALL relapse in the breast without bone marrow involvement, mostly consisting of adolescent girls. Including the present report, a total of 11 cases were analyzed; the onset ages of ALL were a median of 16.5 (range 5-50) years old and the ages of relapse in the breast a median of 20 (range 12-51) years old. Data suggest that, although rare, the breast could become one of the extramedullary relapse sites of ALL developed in adolescent girls.