Osteitis deformans in neoplastic diseases, unsp upper arm

This code describes Paget's disease of bone (osteitis deformans) occurring in a patient with a neoplastic disease, specifically affecting an unspecified upper arm. Paget's disease is a chronic bone disorder characterized by abnormal bone remodeling, leading to enlarged and weakened bones. When it co-occurs with cancer, it can complicate diagnosis and treatment.

Use this code when documentation clearly indicates a diagnosis of Paget's disease of bone in the upper arm, and the patient also has a co-existing neoplastic disease. The medical record should specify the affected upper arm (e.g., "osteitis deformans of the upper arm in a patient with lung cancer").

• Ensure documentation specifies both the osteitis deformans and the presence of a neoplastic disease.
• A separate code for the specific neoplastic disease (e.g., C-code) must be reported as a primary or secondary diagnosis.
• If the laterality of the upper arm is specified (left or right), a more specific code (M90.621 or M90.622) should be used instead.