Well‐differentiated fetal adenocarcinoma of the lung: Cytomorphologic features on fine‐needle aspiration with emphasis on use of β‐catenin as a useful diagnostic marker

Well‐differentiated fetal adenocarcinoma (WDFA), also known as low grade adenocarcinoma of the fetal lung type, is a rare pulmonary neoplasm now considered to be a variant of lung adenocarcinoma rather than a type of pulmonary blastoma. Upregulation of the Wnt signaling pathway with subsequent aberrant nuclear/cytoplasmic β‐catenin expression has been recently described in these tumors providing a possible pathogenetic role for this gene in WDFA. We describe the cytomorphologic findings of a case of WDFA in a 36‐yr‐old female patient and emphasize the diagnostic utility of aberrant nuclear/cytoplasmic expression of β‐catenin as an adjunct to the correct preoperative recognition of this tumor on aspiration cytology. Diagn. Cytopathol. 2007;35:39–42. © 2006 Wiley‐Liss, Inc.