Pathological examinations. (a) Hematoxylin and eosin staining showed moderately differentiated malignant cells with abundant cytoplasm connected with intercellular bridge. Immunohistochemical staining revealed that the tumor cells were strongly positive for p40 (b) and CK5/6 (c). (d) Fluorescence in situ immune-hybridization signals of ALK. Split red and green signals can be observed.