An Unusual Presentation of Extramedullary Relapse Following Blinatumomab in Philadelphia Chromosome-Positive Acute Lymphoblastic Leukemia.

In adult patients, extramedullary relapse (EMR) in B-acute lymphoblastic leukemia (B-ALL) has a pejorative prognosis, especially after allogeneic hematopoietic stem cell transplantation (allo-HSCT). Blinatumomab, a bispecific CD3/CD19 antibody, is approved for relapsed/refractory acute lymphoblastic leukemia (ALL) and has proven its efficacy with good complete response (CR) rates and molecular responses in several trials. Unusual sites of relapse following treatment with blinatumomab for ALL are rarely reported. We describe the case of a 23-year-old male with B-ALL characterized as Philadelphia chromosome-positive without extramedullary lesions at diagnosis. He benefited from a matched-related donor allo-HSCT at first remission. A relapse in the bone marrow and central nervous system was diagnosed four months later. A treatment with blinatumomab was initiated with the obtention of CR after one cycle. During the third cycle of blinatumomab, multiple sites of EMR occurred initially with a painless swelling appearing in the areolas and the nipples, followed by bilateral testicular hypertrophy and moderate paraplegia. A diagnosis of leukemic infiltration on the areola-nipple complex was made by cytological analysis of the fine-needle aspiration of the left areola. The analysis of bone marrow was normal, but molecular BCR-ABL was positive. Systemic chemotherapy with hyper-CVAD (cyclophosphamide, vincristine, doxorubicin, and dexamethasone) and cycles of blinatumomab with nilotinib was initiated in association with intrathecal chemotherapy and whole-brain radiation therapy. Clinical, molecular, and central nervous remissions were obtained. We report this case to describe multiple sites of EMR of B-ALL with atypical breast infiltration in an adult male patient following treatment with blinatumomab.