Uterine serous carcinoma (USC) is an aggressive type of endometrial cancer with a propensity to have extra-uterine spread at diagnosis, in some cases despite limited involvement of the uterus. Serous endometrial intra-epithelial carcinoma (EIC) is a recently recognised entity with the same cytological features and p53 mutations as USC, but it does not demonstrate stromal or myometrial invasion. In addition to representing the putative precursor to USC, the pure form of serous EIC may also be associated with extra-uterine tumour at the time of diagnosis and with risk for recurrence, spread, and eventual death from tumour. Current evidence indicates that serous EIC is a form of minimal USC with behaviour that is stage dependent, thereby necessitating complete surgical staging despite limited disease in the uterus. We review the diagnostic criteria for minimal USC, pitfalls in the differential diagnosis, and discuss a practical approach to evaluating biopsies, polypectomies, or hysterectomies containing minimal USC.