On hospitalization, the clinical examination of a 64-year-old female with polyarthralgia and an elevated fever revealed leukocytosis, an increased lactic acid dehydrogenase level, and a positivity for the C-reactive protein. Subsequently, the patient developed muscular pain in the lower limbs. Thus, a muscle biopsy was performed and B-cells with atypia were detected in the arteriolar lumen within the muscle. This led to the diagnosis of angiotropic lymphoma (AL). A combination chemotherapeutic regimen was initiated, and the patient's symptoms disappeared. AL is difficult to diagnose before death, but in this case, muscle biopsy facilitated an early diagnosis and subsequent chemotherapy resulted in the disappearance of the AL. We thus feel this report may be of value.