Cytological Features of Dedifferentiated Adenoid Cystic Carcinoma of the Trachea: A Case Report

Adenoid cystic carcinoma (AdCC) is a distinct type of carcinoma, and cytological examination has been recognized as a useful tool in its diagnosis. Dedifferentiation is defined as the abrupt transformation of a low-grade tumor into a tumor with high-grade components. Albeit extremely rare, dedifferentiated AdCC has been reported: however, the cytological features of this tumor have not been documented. We observed a case in which a 66-year-old Japanese male had stenosis and thickness of the lower tracheal and bronchial walls. Cytological smears of a bronchial brush specimen revealed features typical for low-grade AdCC. However, a few cohesive epithelial cell clusters composed of large, atypical polygonal cells with large nuclei and conspicuous nucleoli also were present. This component was considered to represent dedifferentiated carcinoma. Histopathological study of the resected bronchial tumor revealed dedifferentiated AdCC. The cytological diagnosis of conventional low-grade AdCC is straightforward in most cases, although extremely rare, dedifferentiated carcinoma can occur within the conventional AdCC, and detection of a dedifferentiated component is possible in a cytological specimen because of obvious nuclear atypia. Therefore, careful observation is needed because cytologic diagnosis of dedifferentiated AdCC can help expedite treatment of this highly aggressive tumor. Diagn. Cytopathol. 2014;42:880-883. (c) 2013 Wiley Periodicals, Inc.