Fig. 2.

The histological findings in Case 2.

(A–C) 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 at 11 months after the initial diagnosis. An EGFR T790M mutation was detected in this specimen (B). SCLC transformation was identified in the second re-biopsy 33 months after the initial diagnosis (8 months after the final dose of EGFR-TKI) (C). (D–F) Immunostaining for synaptophysin. While the tumor cells obtained at the initial biopsy and first re-biopsy were negative for synaptophysin (D and E), the tumor cells from the second re-biopsy were positive (F). Bar indicates 100 μm.