A Case of Breast Cancer in a Patient with a Congenital Pectoralis Muscle Defect.

Congenital pectoral muscle defects are very rare, and when accompanied by limb defects, they are called Poland syndrome. A woman in her 70s, 4 years after partial mastectomy for breast cancer, underwent mastectomy for a local recurrence. During the operation, the pectoralis major and minor muscles were found to be defective. However, the patient did not have any limb defects. Although congenital pectoral muscle defects are very rare, it would be better to confirm defects of the pectoral muscle by preoperative diagnostic imaging such as CT because the postoperative treatment may be affected.