Aneurysmal bone cyst, unspecified thigh

This code describes an aneurysmal bone cyst (ABC) located in an unspecified region of the thigh bone. An ABC is a benign, expansile, osteolytic lesion of bone, characterized by blood-filled spaces separated by fibrous septa containing osteoclast-like giant cells and reactive woven bone.

Use this code when documentation confirms an aneurysmal bone cyst affecting the thigh, but the specific laterality (right or left) is not documented. Supporting documentation would include imaging reports (X-ray, MRI) and pathology reports confirming the diagnosis and location.

• Ensure the documentation specifies "thigh" and not a more precise anatomical location within the femur (e.g., femoral shaft, distal femur), which would require a more specific code.
• Avoid using this code if laterality (right or left thigh) is clearly documented; instead, select the appropriate M85.551 or M85.552 code.
• Confirm that the lesion is indeed an aneurysmal bone cyst and not another type of bone cyst or tumor, as misidentification can lead to incorrect coding.