M85.521 (Aneurysmal bone cyst, right upper arm) compared with M85.529 (Aneurysmal bone cyst, unspecified upper arm), from the official CMS tabular data. M85.521 and M85.529 code the same condition on opposite sides. MedCoder-derived
Same condition; these differ only in which side is documented.
These codes share a category and title and differ only in the side affected. The documentation decides which applies, and a bilateral code is reported only where the code set provides one.
Source: ICD-10-CM tabular list (laterality variant derived from the code title)
Same condition, opposite side. M85.521 and M85.529 name the same condition on opposite sides of the body.
Same category and title, differing only in which side is affected — the documentation decides which one applies, and a bilateral code is reported only where the code set provides one.
| M85.521Aneurysmal bone cyst, right upper arm | M85.529Aneurysmal bone cyst, unspecified upper arm | |
|---|---|---|
| Billing status | Billable | Billable |
| Classification | M00-M99 — Diseases of the musculoskeletal system and connective tissue | M00-M99 — Diseases of the musculoskeletal system and connective tissue |
| Definition | Aneurysmal bone cyst, right upper arm is a billable ICD-10-CM diagnosis code (M85.521). | Aneurysmal bone cyst, unspecified upper arm is a billable ICD-10-CM diagnosis code (M85.529). |
Derived from the official CMS ICD-10-CM tabular data (FY2026). Not billing advice; verify sequencing rules for the encounter. All data sources