Aneurysmal bone cyst, left ankle and foot

This code signifies a benign, expansile, and often hemorrhagic bone lesion characterized by blood-filled spaces separated by fibrous septa, specifically located in the bones of the left ankle and foot. It represents a non-neoplastic, osteolytic lesion that can cause pain, swelling, and pathological fractures.

Apply this code when documentation clearly indicates a diagnosis of an aneurysmal bone cyst affecting the left ankle or foot. This diagnosis is typically confirmed by imaging studies (X-ray, MRI) and often a biopsy. Use this code for both initial encounters and subsequent treatment of this specific condition in the specified anatomical location.

• Ensure laterality is explicitly documented as "left" for the ankle and foot.
• Differentiate from other benign bone tumors or cysts; documentation should specify "aneurysmal bone cyst."
• If a pathological fracture is present due to the cyst, sequence the fracture code first, followed by this code as an underlying condition.