We report a case of fetal adenocarcinoma of the lung in a 70-year-old woman whose bronchial washing cytology showed many large overlapping palisaded tumor cell clusters. Cells had round or oval nuclei with fine granular chromatin and indistinct nucleoli. Cytology also showed two other small cluster types-one with nuclear molding and the other with clear cytoplasm and round nuclei with hypochromasia. The differential diagnosis included low-grade lung adenocarcinoma, metastatic adenocarcinoma, pulmonary blastoma, and carcinoid tumor. This case suggests that fetal adenocarcinoma shows a variety of clusters in bronchial washing cytology.
