ERBB2 and breast carcinoma: Among patients with breast cancer, our study agrees with prior reports that IMD is too rare to warrant routine screening, but screening may be justified for patients with metastatic HER2+ or metastatic triple-negative breast cancer.27,28 Regardless, breast cancers are more likely to metastasize to other parts of the body before reaching the brain, so extramammary screening in this group should also include standard investigations for lung, liver, and bone metastases.12