A variety of uncommon malignant endometrial tumors can be challenging to diagnose because of overlapping morphology with more common entities. In some cases, immunohistochemical stains and/or molecular testing allow for more definitive diagnosis or prognostication.


To review classic morphologic features of uncommon endometrial tumors, pathologic features of these tumors and their mimics, and the evidence for use of immunohistochemistry and molecular testing in the diagnosis of these tumors.

Data Sources.—

University of Michigan (Ann Arbor) cases and review of pertinent literature about each entity.


Although each of these uncommon endometrial tumors has morphologic mimics, key histologic features, immunohistochemical stains, and molecular testing allow for accurate classification.

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Competing Interests

The authors have no relevant financial interest in the products or companies described in this article.

Author notes

Presented at the New Frontiers in Pathology Conference; October 26–28, 2022; Ann Arbor, Michigan.