[Extranodal B-cell lymphoma in the distal femur with pre-existing CRMO].

CRMO is a rare form of nonbacterial osteomyelitis, which is mainly found in children. The diagnosis is complex because bone tumors or lymphoma must also be excluded. The case report describes the development of a solitary femoral lymphoma on the basis of a known CRMO disease as well as the differential diagnostic pitfalls.