ABSTRACT A 17‐year‐old Japanese male patient was referred to our hospital due to an erythematous tumor on part of the right mandible that had developed 3 months earlier, and similar tumors had appeared on the trunk and lower extremities. A complete blood count showed no specific abnormalities. Histopathological findings of a biopsy specimen from the erythematous tumor on the right thigh showed a nodular or diffuse infiltrate of medium‐sized, mitotic blast‐like cells in the deep dermis. Immunohistochemistry showed that CD10, CD20, TdT, CD79a, and PAX5 were positive, and CD3, CD4, and CD8 were negative. A complete PET/CT examination showed that Waldeyer's ring and the right ulna demonstrated intense 18 F‐FDG uptake, along with hyperdense multiple nodularity in cutaneous or subcutaneous lesions on the trunk and lower legs. Bone marrow infiltration was not observed. These findings led to the diagnosis of B‐LBL not further classified. The patient received chemotherapy with methotrexate, L‐asparaginase, vincristine, daunorubicin, cytarabine, and mercaptopurine. The multiple cutaneous and subcutaneous tumors disappeared after the initial treatment.
Shimizu et al. (Fri,) studied this question.