[Endometrioid adenocarcinoma with proliferated stromal cells, hyalinization and cord-like formations: A case report]

Corded and hyalinized endometrioid carcinoma (CHEC) is a morphologic variant of endo-metrioid adenocarcinoma. The tumor exhibits a biphasic appearance with areas of traditional low-grade adenocarcinoma merging directly with areas of diffuse growth composed of epithelioid or spindled tumor cells forming cords, small clusters, or dispersed single cells. It is crucial to distinguish CHEC from its morphological mimics, such as malignant mixed mullerian tumor (MMMT), because CHECs are usually low stage, and are associated with a good post-hysterectomy prognosis in most cases while the latter portends a poor prognosis. The patient reported in this article was a 54-year-old woman who presented with postmenopausal vaginal bleeding for 2 months. The ultrasound image showed a thickened uneven echo endometrium of approximately 12.2 mm and a detectable blood flow signal. Magnetic resonance imaging revealed an abnormal endometrial signal, considered endometrial carcinoma (Stage Ⅰ B). On hysterectomy specimen, there was an exophytic mass in the uterine cavity with myometrium infiltrating. Microscopically, most component of the tumor was well to moderately differentiated endometrioid carcinoma. Some oval and spindle stromal cells proliferated on the superficial surface of the tumor with a bundle or sheet like growth pattern. In the endometrial curettage specimen, the proliferation of these stromal cells was more obvious, and some of the surrounding stroma was hyalinized and chondromyxoid, which made the stromal cells form a cord-like arrangement. Immunostains were done and both the endometrioid carcinoma and the proliferating stroma cells showed loss of expression of DNA mismatch repair protein MLH1/PMS2 and wild-type p53 protein. Molecular testing demonstrated that this patient had a microsatellite unstable (MSI) endometrial carcinoma. The patient was followed up for 6 months, and there was no recurrence. We diagnosed this case as CHEC, a variant of endometrioid carcinoma, although this case did not show specific β-catenin nuclear expression that was reported in previous researches. The striking low-grade biphasic appearance without TP53 mutation confirmed by immunohistochemistry and molecular testing supported the diagnosis of CHEC. This special morphology, which is usually distributed in the superficial part of the tumor, may result in differences between curettage and surgical specimens. Recent studies have documented an aggressive clinical course in a significant proportion of cases. More cases are needed to establish the clinical behaviors, pathologic features, and molecular profiles of CHECs. Recognition of the relevant characteristics is the prerequisite for pathologists to make correct diagnoses and acquire comprehensive interpretation.