Oncology & Hematology Coding Alert

Question: If a patient is having a mammogram for a screening, you use the Z12.31. If it is diagnostic you would use the diagnosis for that. My question is, if the screening shows a lesion, how is that diagnosis coded? Is it still considered a screening followed by a mass/lump diagnosis or just an abnormal diagnosis?

AAPC Forum Participant

Answer: You are correct that you would use Z12.31 (Encounter for screening mammogram for malignant neoplasm of breast) if the only reason for the procedure is a screening.

Here’s why: To assign the correct code for this screening mammogram encounter, follow the decision tree accompanying ICD-10-CM guideline I.C.21.c.5 in the AAPC 2024 ICD-10-CM Expert code book. The first question it prompts you is, “Does the patient have a sign or symptom that prompted the test?” If the answer to this question is “yes,” you are told to “report the sign or symptom that prompted the test.”

If the answer is no, then the decision tree tells you to report a screening code first, then to assign a code for the condition incidentally found during the screening as an additional diagnosis.

So, for the encounter you describe, you would not report a sign or symptom as the first-listed diagnosis, as the patient did not report to your provider with a sign or symptom to prompt the screening. Instead, you would report Z12.31 for the screening mammogram, followed by a code such as N63.- (Unspecified lump in breast) to document the incidental mammogram finding.