Dedifferentiated Cervical Mesonephric Adenocarcinoma: Report of 2 Cases of a Previously Undescribed Phenomenon

We report 2 unusual cervical carcinomas, in patients aged 29 and 55, comprising a combination of HPV-independent mesonephric adenocarcinoma and high-grade undifferentiated carcinoma. Immunohistochemistry showed negative staining or marked reduction in staining with epithelial markers (cytokeratins and EMA), PAX8, and GATA3 in the undifferentiated carcinoma component compared with the mesonephric adenocarcinoma component. Molecular testing revealed pathogenic variants (PVs) or likely PVs in KRAS and in the SWI/SNF genes SMARCA4, ARID1A, and ARID1B in 1 case and PVs or likely PVs in KRAS, ARID1A, ARID1B, and PIK3CA in the other. We propose that these neoplasms represent dedifferentiated mesonephric adenocarcinomas. As far as we are aware, this phenomenon of dedifferentiation within a mesonephric adenocarcinoma has not been reported previously. Both tumors exhibited aggressive behavior with rapid local recurrence or metastasis of the undifferentiated carcinoma component. PVs in SWI/SNF genes may be associated with the process of dedifferentiation.