Metastatic poorly differentiated pulmonary adenocarcinoma before (A, B) and 8 months after starting crizotinib treatment (C, D). A: In inguinal lymph node before initiation of crizotinib treatment (HE, x20). B: Serial section of sample in A with strongly positive anaplastic lymphoma kinase immunostaining in the metastatic tumor tissue (5A4 mAb, x20). C: Anaplastic lymphoma kinase-positive immunostaining in newly appeared inguinal lymph nodal metastasis after 8 months of crizotinib treatment (5A4 mAb, x20). D: Fluorescence in-situ hybridization analysis of preserved anaplastic lymphoma kinase rearrangement in newly appeared inguinal lymph nodal metastasis after 8 months of crizotinib treatment. Representative tumor cell nucleus with one normal fusion signal and one single red/orange signal (Oil, x60).