Fig. 1.

The histological findings in Case 1.

(A–D) Hematoxylin and Eosin staining of biopsy specimens. The patient was diagnosed with adenocarcinoma based on the evaluation of the initial biopsy specimen (A). Adenocarcinoma was identified in the first re-biopsy performed at 16 months after the initial diagnosis (B). Adenocarcinoma was also identified in the second re-biopsy at 32 months after the initial diagnosis (C). SCLC transformation was identified in the third re-biopsy at 42 months after the initial diagnosis (10 months after the final dose of EGFR-TKI) (D). (E–G) Immunostaining for synaptophysin. While the tumor cells obtained in the first and second re-biopsies were negative for synaptophysin, a representative SCLC marker (E and F), the tumor cells from the third re-biopsy were positive (G). Bar indicates 100 μm.