Introduction Administration of immune checkpoint inhibitors (ICIs) induces different patterns of response, including the classical complete or partial response and disease progression and new patterns such as hyperprogressionand pseudoprogression. Pseudoprogression is defined as an increase in tumor size followed by a response to treatment, resulting from an exacerbated immune cell infiltration in the tumor bed, including CD103+ and CD8+ cells [Citation1]. Pseudoprogression is a rare phenomenon, with a rate not exceeding 10% in patients treated with ICI [Citation2]. In everyday practice, the misclassification of pseudoprogression as disease progression remains a concern. According to iRECIST guidelines, confirmation of the progression with later imaging is mandatory to make sure that the 'unconfirmed' progression is 'disease progression' and not 'pseudoprogression' [Citation3]. Hodi et al. [Citation4] described that pseudoprogression occurs more often at the beginning of ICI treatment. Here, we report two cases of dramatic pseudoprogression occurring 36 and 10 months after the initiation of ICI.