Endometrioid Adenocarcinoma Resembling Cutaneous Pilomatrix Carcinoma: A Case Report of an Aggressive Neoplasm in a Young Woman With Diffusely Aberrant Beta-catenin Expression and Associated Morular Metaplasia and Atypical Polypoid Adenomyoma-type Change.

Endometrioid carcinoma with histopathologic resemblance to cutaneous pilomatrix carcinoma with mutations in the gene encoding beta-catenin, CTNNB1 are rare. There are minimal numbers of reports of high-grade tumors with this divergent differentiation in the literature. We report the case of a 29-yr-old female with an unusual presentation of endometrial cancer with overall histologic appearance indicative of a recently reported aggressive subtype of Federation of Gynecology and Obstetrics (FIGO) IVB grade 3 endometrioid carcinoma with features resembling cutaneous pilomatrix carcinoma. She was treated with a primary chemotherapy regimen with an initial significant response to treatment before developing symptomatic brain metastasis for which she underwent whole-brain radiotherapy. We discuss the unusual histologic and radiologic presentation as well as her individual management throughout this case report. The apparent association with morular metaplasia and atypical polypoid adenomyoma suggests that this rare carcinoma is within a spectrum of lesions associated with aberrant beta-catenin expression/beta-catenin mutation. Its aggressive nature highlights the importance of early recognition of this rare lesion.