Multifocal peripheral nerve involvement associated with multiple myeloma.

Infiltration of myeloma cells along the peripheral nerve is extremely rare, while multiple myeloma occasionally infiltrates the central nervous system. We present details of a patient in whom multiple myeloma had infiltrated a branch of the femoral nerve of the right inguinal region as well as the left ulnar nerve. The infiltration formed soft tissue masses, with the thickened nerves shown to be penetrating the center of the masses on ultrasonography and magnetic resonance imaging.