Unusual manifestations of renal cell carcinoma

The imaging characteristics of renal cell carcinoma (RCC) vary widely, with masses ranging from cystic to solid, from homogeneous to heterogeneous and necrotic, from small to large, and from localized to extensive. Although the usual imaging features of RCC are well known to radiologists, various unusual imaging features can be particularly misleading; therefore, both usual and unusual imaging features should always be carefully assessed. In this pictorial review, we describe the following unusual imaging features: unusual subtypes, unusual tumor growth, unusual underlying disease, multiple and bilateral presentations, hemorrhage and arteriovenous fistula (AVF)-related presentations, and mimicking of benign tumors. Familiarity with the imaging features of both usual and unusual RCCs will facilitate prompt and accurate diagnosis and treatment.