Abstract:

Mesonephric-like adenocarcinoma (MLA) in the corpus uteri is a highly aggressive malignant tumor, which is easily confused with other types of endometrial cancer. When the tumor morphology and cellular characteristics are not consistent with the clinical biological behavior, attention should be paid to it. This study is to investigate the clinicopathologic features of MLA in the corpus uteri. Three cases of MLA in the corpus uteri diagnosed in the First Affiliated Hospital of Xi'an Jiaotong University from 2020 to 2023 were studied by clinical data, microscopic features and immunohistochemistry. The related literature was reviewed. The clinical manifestations of the three cases of MLA in the corpus uteri were nonspecific. One case was from our hospital and the other two cases were from other hospitals. The age range was 54-58 years. In the specimen description, there was a diffusely growing mass in the endometrium of the uterus, with an uneven surface and tough texture. The muscle wall was extensively invaded. At low magnification, the tumor cells were arranged in tubular, glandular, papillary, micropapillary and solid growth patterns. At high magnification, the cells lining the lumen were arranged in a single layer, cuboidal or columnar pattern, with mild to moderate atypia, with vesicular nuclei and nuclear furrows. Some of the lumens showed eosinophilic homogeneous pink staining without structural-like material. In the solid area, the cells were plat fusiform, arranged in bundles or whirlpools, with large nuclear atypia and frequent mitotic figures. A large number of intravascular cancer thrombus were observed in all the three cases. The tumor cells were positive for GATA3 and/or thyroid transcription factor-1 (TTF1), diffusely positive for pair box gene 2 (PAX2) and PAX8, and positive for CD10 in some luminal margins. Estrogen receptor (ER) was focal positive, and progesterone receptor (PR) was negative. KRAS mutation was detected in case 1. According to the 2023 updated International Federation of Gynecology and Obstetrics (FIGO) staging guidelines for endometrial cancer, all the three cases were in advanced stage. It is suggested that pathologists should make accurate diagnosis based on morphological manifestations, using a set of matched immunohistochemical markers and necessary molecular tests to avoid misdiagnosis and better guide clinical diagnosis and treatment.

Key words: Uterus, Mesonephric-like adenocarcinoma, Clinical pathology