Malignant neoplasm of breast Use additional code to identify estrogen receptor status (Z17.0,Z17.1) ICD-9 174.9 Malignant neoplasm of breast unspecified site ICD-10 C50 Malignant neoplasm of breast of unspecified site, female C50.911 ….. right female breast C50.919 ….. left female breast C50.919 ….. unspecified female breast