RT Journal Article SR Electronic T1 Granulation Tissue-induced Pseudo-relapse During Nivolumab Treatment in Advanced Non-small Cell Lung Cancer JF In Vivo JO In Vivo FD International Institute of Anticancer Research SP 2113 OP 2115 DO 10.21873/invivo.11711 VO 33 IS 6 A1 CHIHIRO ANDO A1 EIKI ICHIHARA A1 HIROHISA KANO A1 YOSHITAKA IWAMOTO A1 ATSUKO HIRABAE A1 TAKAMASA NAKASUKA A1 YOSHINOBU MAEDA A1 KATSUYUKI KIURA YR 2019 UL http://iv.iiarjournals.org/content/33/6/2113.abstract AB Atypical tumor responses such as pseudo-progression or hyper-progression sometimes occur during immune check point inhibitor therapy. Distinct from both responses, we experienced a case of non-small cell lung cancer (NSCLC) with a pseudo-relapse, in which development of granulation mimicked cancer relapse during nivolumab therapy. A male with advanced NSCLC started nivolumab as a second-line therapy. After 15 cycles of nivolumab with a complete response, tumor markers started increasing and positron-emission computed tomography indicated a hot spot in the sigmoid colon. Laparoscopic segmental sigmoid colon resection revealed granulation tissue without any relapse of malignant cells. The results showed that even if radiographical tumor progression is found during immune therapy, histological confirmation should be considered.