OBJECTIVETo analyze the clinicopathological characteristics of patients with anaplastic lymphoma kinase (ALK) rearrangements in lung adenocarcinoma, and the clinical therapy and prognosis of the patients.

METHODSClinicopathological data of 34 cases of ALK-positive patients treated in the Beijing Chest Hospital from 2005 to 2014 were reviewed. The expression of ALK proteins in the resected tumors was detected by immunohistochemistry, and EGFR mutations were examined by polymerase chain reaction and a direct DNA sequencing method.

RESULTSAmong the 34 patients, 20 were male and 14 were female, the median age was 49, and 11 were smokers and 23 were never smokers. The clinical stages of the patients were stage IA in 5 patients, IB in one patient, IIA in two patients, IIIA in 16 patients, IIIB in 5 patients, IV in 4 patients, and one patient of unknown stage. ALK-positive tumors showed strong granular staining in cell cytoplasm by immunohistochemistry. Forteen patients were solid predominant subtype with mucin production, 10 of acinar predominant subtype, 6 of papillary predominant subtype, 3 of micropapillary predominant subtype, and one was of colloid variant. There were 18 cases with mucin production, 6 cases had signet-ring cell morphology, and 10 cases showed cribriform pattern. Only one patient had coexistence of ALK rearrangement and EGFR mutation (L858R at exon 21). Of the 34 patients, 24 patients were followed up. The median follow up of the 24 patients was 11.0 months (1.7-48.7 months).

CONCLUSIONSALK-positive tumors as a molecular subtype of lung adenocarcinoma have distinct clinicopathological features. The histological findings of ALK-positive tumors are characterized by solid predominant subtype with mucin production, acinar predominant subtype, signet-ring cells and cribriform structures. They were rarely co-mutated with EGFR mutation.