Osteitis deformans in neoplastic diseases, left lower leg

This code describes Paget's disease of bone (osteitis deformans) occurring as a manifestation or complication of a neoplastic disease process, specifically affecting the left lower leg. It indicates a secondary form of Paget's disease, where the underlying malignancy is a contributing factor to the bone remodeling disorder.

Use this code when documentation clearly links osteitis deformans in the left lower leg to an existing neoplastic condition. This typically applies when a patient with cancer develops Paget's disease, and clinical findings or imaging confirm the involvement of the left lower leg. Documentation should specify the laterality and the causal relationship to the neoplasm.

• Always sequence the underlying neoplastic disease code first, as M90.662 is a manifestation code.
• Ensure documentation specifies "left lower leg" to support the laterality and site specificity.
• Differentiate from primary Paget's disease (M88.-) which is not associated with neoplastic disease.