Aneurysmal bone cyst, unspecified upper arm

This code signifies the presence of an aneurysmal bone cyst (ABC) located in an unspecified region of the upper arm. An ABC is a benign, expansile, osteolytic bone lesion characterized by blood-filled spaces separated by fibrous septa, often presenting with pain and swelling.

Apply this code when documentation confirms an aneurysmal bone cyst affecting the humerus or other unspecified bone within the upper arm. This code is appropriate when the specific location within the upper arm (e.g., proximal, distal) is not documented.

• Ensure documentation clearly states "aneurysmal bone cyst" and specifies the upper arm as the affected site.
• Avoid using this code if a more specific location within the upper arm (e.g., humerus, radius, ulna) is documented; instead, use a more precise code from the M85.52- subcategory.
• Consider sequencing this code as a primary diagnosis when the ABC is the reason for the encounter, or as a secondary diagnosis if it's an incidental finding or comorbidity.