74 year-old man with right epithelioid malignant pleural mesothelioma (cT2N0M0), who previously received six cycles of first-line chemotherapy (pemetrexed + cisplatin) and then 12 cycles of nivolumab as second-line chemotherapy. (a) Pre-nivolumab treatment FDG-PET/CT shows multiple areas of strong FDG uptake in areas of right pleural lesions (arrows). (b) Pre-nivolumab treatment contrast-enhanced CT shows mass-forming thickness of right pleura (arrows). (c) Post-treatment FDG-PET/CT after 12 cycles of nivolumab shows remarkable progression of multiple pleural lesions (arrows) and appearance of new pleural lesions. (d) Post-treatment contrast-enhanced CT after 12 cycles of nivolumab shows remarkable progression of pleural lesions (arrows). EORTC, PERCIST, imPERCIST, and CT criteria (modified RECIST and RECIST 1.1) indicated PMD or PD due to remarkable progression and appearance of new lesions. In FDG-PET/CT results, the SULpeak sum of the five highest level pleural lesions was increased by 98.6%. In CT findings, the sum size of six pleural lesions perpendicular to the chest wall was increased by 40.3%. According to the second (c) FDG-PET/CT and (d) contrast-enhanced CT result, the patient started another chemotherapy series (irinotecan + gemcitabine), though was alive at 13.9 months after initiation of nivolumab.