Bosniak Category III Renal Cysts Caused by Crizotinib in an Anaplastic Lymphoma Kinase Gene-Rearranged Non-Small Cell Lung Cancer Patient.

Bosniak category III renal cystic masses are often treated with surgical resection because of high risk of malignancy. Crizotinib is an anaplastic lymphoma kinase (ALK) inhibitor used to treat ALK gene-rearranged non-small cell lung cancer and reported to be associated with complex renal cyst formation. We herein report a case of Bosniak category III renal cysts occurred in a crizotinib-treated ALK gene-rearranged non-small cell lung cancer patients. The cysts regressed spontaneously after cessation of crizotinib and we could thus avoid unnecessary surgical resection.