Solitary bone cyst, unspecified ankle and foot

This code signifies the presence of a single, benign, fluid-filled or fibrous lesion within the bone structure of an unspecified ankle or foot. These cysts are typically asymptomatic and often discovered incidentally on imaging studies. They represent a localized area of bone resorption or abnormal bone formation without evidence of malignancy.

Use this code when documentation confirms a solitary bone cyst in the ankle or foot, and the specific laterality (right or left) is not documented or is unknown. This code is appropriate for incidental findings on X-rays, CT scans, or MRIs where the lesion is characterized as a simple bone cyst. Ensure the physician's notes clearly state "solitary bone cyst" and do not specify a particular ankle or foot.

• Avoid using this code if the laterality of the ankle or foot is specified; instead, use the more specific codes for right (M85.471) or left (M85.472).
• Do not use this code for aneurysmal bone cysts (M85.5-), unicameral bone cysts (M85.6-), or other specified bone cysts.
• Ensure documentation explicitly states "solitary" to differentiate from multiple bone cysts or other bone lesions.