Aneurysmal bone cyst, right upper arm

This code signifies an aneurysmal bone cyst (ABC) located specifically in the right upper arm. An ABC is a benign, expansile, osteolytic bone lesion characterized by blood-filled spaces separated by fibrous septa containing osteoclast-like giant cells. It typically presents as a rapidly growing, painful mass.

Use this code when documentation clearly identifies an aneurysmal bone cyst affecting the humerus or other bones of the right upper arm. This diagnosis is often confirmed by imaging studies (X-ray, MRI) showing characteristic lytic lesions with fluid-fluid levels, and sometimes by biopsy.

• Ensure laterality is precisely documented; do not use this code for left upper arm or unspecified upper arm involvement.
• Distinguish from other benign bone tumors or cysts, such as unicameral bone cysts (M85.4-).
• Code any associated pathological fracture separately if present, using an appropriate fracture code.