OBJECTIVETo study the cytomorphologic features of anaplastic lymphoma kinase (ALK)-rearranged pulmonary adenocarcinoma.

METHODSThe morphologic features in 153 pulmonary adenocarcinoma cytology specimens encountered during the period from September, 2011 to April, 2015 in Shanghai Cancer Hospital were retrospectively reviewed. Fluorescence in-situ hybridization (FISH) and/or immunohistochemistry (Ventana D5F3) for ALK gene rearrangement were carried out. The samples studied included 34 pleural effusion specimens, 40 endobronchial ultrasound-guided transbronchial needle aspirates (EBUS-TBNA) and 79 fine needle aspirates of palpable masses on body surface.

RESULTSThirty-nine cases (25.5%) of ALK-rearranged samples were identified by FISH and/or immunohistochemistry, including 3 cases diagnosed by FISH and 36 cases by both technologies. The median age of the ALK-positive group was 50 years, significantly younger than that of the ALK-negative group (60 years old, P = 0.002). Only 4 of the ALK-positive patients were smokers, which was significantly less than that of the ALK-negative group (P < 0.01). In ALK-positive group, 3 cases showed cribriform pattern with prominent nucleoli, 3 cases showed cribriform pattern with mucin-rich cells and 8 cases showed extracellular mucus with mucin-rich cells. The above cytomorphologic patterns were significantly less common in ALK-negative tumors (P < 0.01).

CONCLUSIONSALK-rearranged lung adenocarcinoma is associated with certain distinctive morphologic patterns, including cribriform architecture, presence of prominent nucleoli, mucin-rich cells and extracellular mucus, which can be observed in cytology specimens (including conventional smears and cell block sections). These findings, when combined with clinical features, may give clues to detection of ALK-positive cases.