[Lymphoma misinterpreted as osteomyelitis].

Patients are admitted based on a tentative diagnosis. If that is incorrect it may have negative consequences for the patient and the system. In this case we present an eight-month elucidation with several diagnostic procedures with a tentative diagnosis of osteomyelitis. This diagnosis was kept despite contradicting diagnostic results. Finally, the patient was diagnosed with peripheral T-cell lymphoma. Many cognitive diagnostic pitfalls are known to delay diagnosis. We recommend having them in mind and seeking quick interdisciplinary help when treatment is not successful.