Question: The patient had a breast biopsy that revealed atypical ductal dysplasia. The surgeon scheduled a bilateral simple mastectomy (19180-50) at the request of the patient, who has a family history of breast cancer. What are the correct diagnosis codes for atypical ductal dysplasia and family history of breast cancer? Vermont Subscriber Answer: The diagnosis codes that support the simple mastectomy can be arranged to provide an easy-to-follow trail of medical necessity. The primary diagnosis is the dysplasia, which is a neoplasm of uncertain behavior (238.3) and provides medical necessity for the mastectomy of the breast with the neoplasm. The next diagnosis, V50.41 (Prophylactic organ removal; breast), informs the carrier that the second mastectomy was performed preventively. The third diagnosis, V16.3 (Family history of malignant neoplasm; breast), explains why the preventive mastectomy was performed. Note: The second mastectomy is subject to bilateral procedural guidelines, which means it will be reduced by 50 percent by the Medicare carrier.