[Lumbago as a presentation of B-cell lymphoma invading psoas muscle].

A 73-year-old male had severe lumbago and right inguinal lymphadenopathy. A CT scanning of his abdomen showed marked enlargement of right psoas and erector spinae muscles. The biopsies of the lymph node and the muscles revealed non-Hodgkin's lymphoma of follicular mixed type with muscle invasion. THP-COPE therapy was begun. The swelling of the muscles diminished and the lumbago resolved rapidly. It was reported that clinically prominent infiltration of of lymphoma in skeletal muscle was rarely and psoas muscle was for the most part. We have to consider that psoas muscle invasion of lymphoma cause hard to cure lumbago.