Cytologic Features of ALK-Positive Pulmonary Adenocarcinoma

BACKGROUND: The aim of this study was to determine the cytologic features of anaplastic lymphoma kinase (ALK) expressing pulmonary adenocarcinoma. METHODS: We analyzed the cytopathological findings of 15 cases of endobronchial ultrasound guided aspiration and a case of bronchial washing. These cases were selected based on the histomorphology of ALK-rearranged lung adenocarcinoma. RESULTS: Cytology showed mucinous (81.3%) and hemorrhagic (50%) backgrounds. The cells were arranged in tubulopapillary or tubulocribriform patterns (93.8%), and clusters (56.3%) admixed with signet ring cell features (87.5%). The tumor cells were monotonous and uniform with vesicular nuclei and a small nucleolus. CONCLUSIONS: The characteristic findings were sheets showing a tubulopapillary or tubulocribriform appearance, with vesicular nuclei and a bland chromatin pattern (p<0.001). Scattered signet ring cells were helpful in suggesting ALK-positive adenocarcinoma (p<0.001).