Aneurysmal bone cyst, left forearm

This code describes an aneurysmal bone cyst (ABC) located specifically in the left forearm. An ABC is a benign, expansile, osteolytic bone lesion characterized by blood-filled spaces separated by fibrous septa and osteoclast-like giant cells. It is a non-neoplastic lesion that can cause pain, swelling, and pathological fractures.

This code is appropriate for documenting a confirmed diagnosis of an aneurysmal bone cyst affecting the left forearm. Documentation should clearly specify the location as the left forearm, often supported by imaging studies (e.g., X-ray, MRI) and potentially biopsy results confirming the characteristic histological features of an ABC.

• Ensure laterality is accurately documented and coded; this specific code is for the left forearm.
• Distinguish from other benign bone tumors or tumor-like lesions, such as giant cell tumor of bone or fibrous dysplasia, which have different ICD-10-CM codes.
• If the specific bone within the forearm (e.g., radius, ulna) is documented, review the ICD-10-CM index for more specific codes if available, though M85.532 is generally appropriate for the forearm as a region.