Metastatic mesonephric-like endometrial adenocarcinoma diagnosed on transbronchial needle aspirate cytology.

Mesonephric-like adenocarcinoma is a relatively rare neoplasm with morphology similar to mesonephric adenocarcinoma but unassociated with mesonephric remnants. Its relatively recent description and rarity make it difficult to diagnose, but it has a high rate of distant metastasis, making distinction from endometrioid carcinoma important. Descriptions of its cytologic features are particularly limited. We describe a case of mesonephric-like adenocarcinoma diagnosed on transbronchial needle aspiration of the lung, that had been misdiagnosed as endometrioid endometrial adenocarcinoma on a prior hysterectomy. We discuss the characteristic cyto and histomorphology, immunoprofile, molecular alterations, and clinical significance of this uncommon tumor.