To determine the expression pattern of Twist2 in breast carcinomas, we performed immunohistochemical staining of Twist2 on a tissue microarray that includes 7 cases of normal breast tissue, 6 cases of fibroadenoma, 13 cases of mammaryadenosis, 16 cases of mastitis, and 141 cases of breast cancer. The gene discussed is TWIST2; the disease is mastitis.