Borderline tumors begin as ovarian surface epithelium and progress to low-grade serous, endometrioid, clear cell, and mucinous carcinomas by mutation and change of certain genes such as KRAS, BRAF, NRAS, HER2, CTNNB1, BRAF, ERBB2, ARID1A, PIK3CA, PTEN, HER2, and others. The gene discussed is ERBB2; the disease is mucinous adenocarcinoma.