Complex renal cysts combined with hemorrhage during crizotinib treatment for ALK-rearranged lung adenocarcinoma

The oral small-molecule tyrosine kinase inhibitor (TKI), crizotinib has been approved as a first-generation anaplastic lymphoma kinase (ALK) inhibitor in treatment of advanced ALK-positive non–small cell lung cancer (NSCLC). Recently, development of complex renal cysts has been reported with crizotinib usage, highlighting the importance of accurate differentiation between complex renal cysts and new metastasis in NSCLC. Here we describe a case study with confirmed EGFR wild-type and ALK-rearranged lung adenocarcinoma who developed complex renal cysts combined with hemorrhage during crizotinib treatment, with no abnormal clinical symptoms or kidney functions observed. Interestingly, without crizotinib treatment termination or reduction, the complex hemorrhagic renal cysts regressed with self-limiting and healing. The combined usage of ultrasound, CT and MRI techniques in the presented case allowed proper monitoring of the internal changes within complex renal cysts. The patient provided written informed consent authorizing publication of clinical case. Thus, better understanding of the imaging features of crizotinib-related renal cysts combined with hemorrhage would avoid misdiagnoses as a new metastatic renal mass or the aggravation of the primary disease, therefore avoiding further invasive investigation.