ERBB2 and endometrial serous adenocarcinoma: In another study of 93 uterine serous carcinomas, of which 71 were tested on resected specimens using the 2018 ASCO/CAP criteria, only 4% had an IHC score of 3+, 25% had a FISH ratio ≥2, and 4% were deemed amplified based on a HER2 copy number ≥6 [34].