ALK and lung cancer: In correlation with all clinical information, including the anatomic sites of sample collection, the inconsistent ALK FISH results may be attributable to the complexity of lung cancer that can present in multiple forms, such as multiple primary lung cancer lesions, or may reflect intra- and inter- tumor heterogeneity, as can be manifested as distinct tumor morphologies, genetic profiles, and response to various therapies [17,18,19,20].