Cystic renal masses are commonly encountered in clinical practice. In 2019, the Bosniak classification of cystic renal masses, originally developed for CT, underwent a major revision to incorporate MRI and is referred to as the Bosniak Classification, version 2019. The proposed changes attempt to (a) define renal masses (ie, cystic tumors with less than 25% enhancing tissue) to which the classification should be applied; (b) emphasize specificity for diagnosis of cystic renal cancers, thereby decreasing the number of benign and indolent cystic masses that are unnecessarily treated or imaged further; (c) improve interobserver agreement by defining imaging features, terms, and classes of cystic renal masses; (d) reduce variation in reported malignancy rates for each of the Bosniak classes; (e) incorporate MRI and to some extent US; and (f) be applicable to all cystic renal masses encountered in clinical practice, including those that had been considered indeterminate with the original classification. The authors instruct how, using CT, MRI, and to some extent US, the revised classification can be applied, with representative clinical examples and images. Practical tips, pitfalls to avoid, and decision tree rules are included to help radiologists and other physicians apply the Bosniak Classification, version 2019 and better manage cystic renal masses. An online resource and mobile application are also available for clinical assistance. An invited commentary by Siegel and Cohan is available online.©RSNA, 2021.
Radiographics : a review publication of the Radiological Society of North America, Inc. 2021 Apr 16 [Epub ahead of print]
Nicola Schieda, Matthew S Davenport, Satheesh Krishna, Elizabeth A Edney, Ivan Pedrosa, Nicole Hindman, Ronaldo H Baroni, Nicole E Curci, Atul Shinagare, Stuart G Silverman
From the Department of Medical Imaging, The Ottawa Hospital, University of Ottawa, 1053 Carling Ave, Ottawa, ON, Canada K1H 1H6 (N.S.); Departments of Radiology (M.S.D., N.E.C.) and Urology (M.S.D.), Michigan Medicine, University of Michigan, Ann Arbor, Mich; Joint Department of Medical Imaging, University Health Network, Mount Sinai Hospital and Women's College Hospital, University of Toronto, Toronto, ON, Canada (S.K.); Department of Radiology, University of Nebraska Medical Center, Omaha, Neb (E.A.E.); Department of Radiology, University of Texas Southwestern Medical Center, Dallas, Tex (I.P.); Department of Radiology, New York University Langone Medical Center, New York, NY (N.H.); Department of Radiology and Diagnostic Imaging, Hospital Israelita Albert Einstein, São Paulo, Brazil (R.H.B.); Department of Radiology, Brigham and Women's Hospital/Dana-Farber Cancer Institute, Harvard Medical School, Boston, Mass (A.S.); and Department of Radiology, Brigham and Women's Hospital, Harvard Medical School, Boston, Mass (S.G.S.).