Crizotinib-Associated Renal Cysts: A Case Series

Crizotinib is an anaplastic lymphoma kinase (ALK) inhibitor, used as a targeted chemotherapeutic agent in ALK-positive cases of nonsmall cell lung carcinoma. Although uncommon, it may be associated with the formation of new renal cysts, which may be simple or complex, or the enlargement of preexisting simple renal cysts or their transformation into complex cysts. These cysts usually regress partially or completely but may rarely enlarge over time or get complicated by infection or abscess formation. Such cases may even require dose reduction or withholding crizotinib. Although documented in clinical literature, this entity is not well known among radiologists. Knowledge of this entity helps in preventing erroneous diagnosis of the new kidney “lesion” as metastasis or disease progression and avoids an unnecessary biopsy. We describe a series of four cases which developed complex renal cysts during treatment with crizotinib to demonstrate this point.