There have been several updates recently on the classification of uterine tumors. Endometrial carcinomas have traditionally been divided into 2 types, but some are difficult to classify and do not fit readily into either of the currently recognized categories. The Cancer Genome Atlas Research Network has recently defined 4 new categories of endometrial cancer on the basis of mutational spectra, copy number alteration, and microsatellite instability, which might provide independent prognostic information beyond established risk factors. The Society of Gynecologic Oncology, moreover, now recommends systematic screening of every patient with endometrial cancer for Lynch syndrome. The new definition of high-grade endometrial stromal sarcoma disregards the number of mitotic figures as a primary diagnostic criterion and instead specifies moderate atypia still resembling stromal origin but lacking the pleomorphism of undifferentiated uterine sarcoma; these tumors also harbor a JAZF1-SUZ12 gene rearrangement. Mitotic count, atypia, and coagulative necrosis are the main histologic criteria that define leiomyosarcoma. Determining the type of necrosis can be very challenging in patients receiving various treatment modalities for symptomatic fibroids before myomectomy, since key histologic features of ischemic-type necrosis are often absent. Ancillary stains including p16, p53, MIB-1, trichrome, and reticulin may be helpful in tumors harboring necrosis that is difficult to classify. Minimally invasive gynecologic surgeries have introduced histologic artifacts that complicate the diagnosis. It is essential to recognize these as procedure-related artifacts to avoid upstaging tumors and triggering unnecessary adjuvant treatment.