Limitations of the L3 skeletal muscle index and the Asian Working Group for Sarcopenia 2019 consensus diagnostic criteria for sarcopenia evaluation in a case of diffuse large B‐cell lymphoma

Sarcopenia is an adverse prognostic factor for diffuse large B‐cell lymphoma. A case of diffuse large B‐cell lymphoma whose diagnosis, severity, and therapeutic effect of sarcopenia were difficult to determine owing to lymphoma cell infiltration into the psoas major and femoral bone marrow is reported. At presentation, the cross‐sectional area of left psoas major at L3 was enlarged owing to lymphoma cell infiltration; thus, sarcopenia evaluation was impossible by L3 skeletal muscle index. The patient was bedridden; thus, sarcopenia evaluation was impossible by the Asian Working Group for Sarcopenia 2019 consensus diagnostic criteria at presentation. At the terminal stage, she could not walk due to bilateral anterior thigh pain caused by lymphoma infiltration into femoral marrow; thus, sarcopenia evaluation was impossible by the Asian Working Group for Sarcopenia 2019 consensus diagnostic criteria. Although the L3 skeletal muscle index and the Asian Working Group for Sarcopenia 2019 consensus diagnostic criteria are representative sarcopenia evaluation systems, they cannot be used to evaluate sarcopenia in some diffuse large B‐cell lymphoma patients.