Cytomorphological Features of Lung Adenocarcinoma with Anaplastic Lymphoma Kinase Gene Rearrangement

BACKGROUND: The anaplastic lymphoma kinase (ALK) gene rearrangement is a predictive and prognostic marker in pulmonary adenocarcinoma. A series of clinical and pathological features have been documented in patients who harbor this translocation. AIMS: The objectives of this study were to analyze the specific cytomorphological features of lung adenocarcinoma that harbored the ALK gene rearrangement and to compare the morphological features with the mutation-negative cases. MATERIALS AND METHODS: The study sample of 40 cases included 15 ALK-positive cases and 25 ALK-negative cases. After the diagnosis was established, testing for ALK rearrangement was on the histopathology sample. The corresponding fine-needle aspiration cytology slides were retrieved from the records and cytomorphological features were analyzed. RESULTS: A comparison of pattern between the ALK-positive and ALK-negative group revealed that the sheet-like pattern and singly scattered cells were more common in the ALK-positive group. Moderate-to-severe nuclear pleomorphism was identified in 80% of ALK-positive cases and 72% of ALK-negative cases. The presence of mucinous features and/or signet ring morphology was the most striking feature of ALK-positive cases with P value of 0.002. The presence of necrosis in the background was identified in 80% of ALK-positive cases and was statistically significant (P = 0.001). CONCLUSION: This is among the few studies from India, where a detailed analysis of the cytomorphological features of cases with ALK phenotype versus the mutation negative cases has been performed.