Question: Encounter notes indicate that a patient has a solitary bone cyst on their shoulder. What is the best diagnosis code for this patient? Illinois Subscriber Answer: With the information you presented, you can get to M85.41- (Solitary bone cyst, shoulder). You should, however, get more detail so your diagnosis code can go to the 6th character. Do this: Go back and check the encounter notes; then, choose one of the following codes for your claim: