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Bosniak Classification of Cystic Masses
Benjamin Wildman-Tobriner, MD; Kevin Kalisz, MD
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KEY FACTS

  • Terminology

    • Imaging

      • Top Differential Diagnoses

        • Pathology

          • Clinical Issues

            • Diagnostic Checklist

              TERMINOLOGY

              • Abbreviations

                • Renal cell carcinoma (RCC)
              • Definitions

                • Bosniak classification: System for categorization and risk stratification of cystic renal masses
                  • Introduced in 1986, most recently revised in 2019
                • Cystic renal mass: No established definition for what constitutes cystic mass
                  • Bosniak 2019 proposes that < 25% of mass contains enhancing tissue to qualify as cystic
                • Bosniak I: Benign simple renal cyst requiring no follow-up
                • Bosniak II: Benign (or "likely benign") renal cyst (or "mass") requiring no follow-up
                • Bosniak IIF: Large majority benign; follow at 6 months and then annually for 5 years
                • Bosniak III: Intermediate probability of malignancy; urologic consultation should be considered
                • Bosniak IV: Large majority are malignant; urologic consultation should be considered
                • Cyst: Bosniak I simple cysts or Bosniak II masses deemed cysts
                • Cystic mass: Any other cystic lesion

              IMAGING

              • General Features

                • Radiographic Findings

                  • CT Findings

                    • MR Findings

                      • Ultrasonographic Findings

                        • Imaging Recommendations

                          DIFFERENTIAL DIAGNOSIS

                            PATHOLOGY

                            • General Features

                              • Staging, Grading, & Classification

                                • Gross Pathologic & Surgical Features

                                  • Microscopic Features

                                    CLINICAL ISSUES

                                    • Presentation

                                      • Demographics

                                        • Natural History & Prognosis

                                          • Treatment

                                            DIAGNOSTIC CHECKLIST

                                            • Consider

                                              • Image Interpretation Pearls

                                                • Reporting Tips

                                                  Selected References

                                                  1. Tse JR et al: Bosniak classification of cystic renal masses version 2019: comparison of categorization using CT and MRI. AJR Am J Roentgenol. 216(2):412-20, 2021
                                                  2. Atkins MB et al: Epidemiology, pathology, and pathogenesis of renal cell carcinoma. UpToDate. Published June 2021. https://www.uptodate.com/contents/epidemiology-pathology-and-pathogenesis-of-renal-cell-carcinoma
                                                  3. Silverman SG et al: Bosniak classification of cystic renal masses, version 2019: an update proposal and needs assessment. Radiology. 292(2):475-88, 2019
                                                  4. Dillman JR et al: Hereditary renal cystic disorders: imaging of the kidneys and beyond. Radiographics. 37(3):924-6, 2017
                                                  5. Mousessian PN et al: Malignancy rate, histologic grade, and progression of Bosniak category III and IV complex renal cystic lesions. AJR Am J Roentgenol. 209(6):1285-90, 2017
                                                  6. Schoots IG et al: Bosniak classification for complex renal cysts reevaluated: a systematic review. J Urol. 198(1):12-21, 2017
                                                  7. Winters BR et al: Cystic renal cell carcinoma carries an excellent prognosis regardless of tumor size. Urol Oncol. 33(12):505.e9-13, 2015
                                                  Related Anatomy
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                                                  Related Differential Diagnoses
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                                                  References
                                                  Tables

                                                  Tables

                                                  KEY FACTS

                                                  • Terminology

                                                    • Imaging

                                                      • Top Differential Diagnoses

                                                        • Pathology

                                                          • Clinical Issues

                                                            • Diagnostic Checklist

                                                              TERMINOLOGY

                                                              • Abbreviations

                                                                • Renal cell carcinoma (RCC)
                                                              • Definitions

                                                                • Bosniak classification: System for categorization and risk stratification of cystic renal masses
                                                                  • Introduced in 1986, most recently revised in 2019
                                                                • Cystic renal mass: No established definition for what constitutes cystic mass
                                                                  • Bosniak 2019 proposes that < 25% of mass contains enhancing tissue to qualify as cystic
                                                                • Bosniak I: Benign simple renal cyst requiring no follow-up
                                                                • Bosniak II: Benign (or "likely benign") renal cyst (or "mass") requiring no follow-up
                                                                • Bosniak IIF: Large majority benign; follow at 6 months and then annually for 5 years
                                                                • Bosniak III: Intermediate probability of malignancy; urologic consultation should be considered
                                                                • Bosniak IV: Large majority are malignant; urologic consultation should be considered
                                                                • Cyst: Bosniak I simple cysts or Bosniak II masses deemed cysts
                                                                • Cystic mass: Any other cystic lesion

                                                              IMAGING

                                                              • General Features

                                                                • Radiographic Findings

                                                                  • CT Findings

                                                                    • MR Findings

                                                                      • Ultrasonographic Findings

                                                                        • Imaging Recommendations

                                                                          DIFFERENTIAL DIAGNOSIS

                                                                            PATHOLOGY

                                                                            • General Features

                                                                              • Staging, Grading, & Classification

                                                                                • Gross Pathologic & Surgical Features

                                                                                  • Microscopic Features

                                                                                    CLINICAL ISSUES

                                                                                    • Presentation

                                                                                      • Demographics

                                                                                        • Natural History & Prognosis

                                                                                          • Treatment

                                                                                            DIAGNOSTIC CHECKLIST

                                                                                            • Consider

                                                                                              • Image Interpretation Pearls

                                                                                                • Reporting Tips

                                                                                                  Selected References

                                                                                                  1. Tse JR et al: Bosniak classification of cystic renal masses version 2019: comparison of categorization using CT and MRI. AJR Am J Roentgenol. 216(2):412-20, 2021
                                                                                                  2. Atkins MB et al: Epidemiology, pathology, and pathogenesis of renal cell carcinoma. UpToDate. Published June 2021. https://www.uptodate.com/contents/epidemiology-pathology-and-pathogenesis-of-renal-cell-carcinoma
                                                                                                  3. Silverman SG et al: Bosniak classification of cystic renal masses, version 2019: an update proposal and needs assessment. Radiology. 292(2):475-88, 2019
                                                                                                  4. Dillman JR et al: Hereditary renal cystic disorders: imaging of the kidneys and beyond. Radiographics. 37(3):924-6, 2017
                                                                                                  5. Mousessian PN et al: Malignancy rate, histologic grade, and progression of Bosniak category III and IV complex renal cystic lesions. AJR Am J Roentgenol. 209(6):1285-90, 2017
                                                                                                  6. Schoots IG et al: Bosniak classification for complex renal cysts reevaluated: a systematic review. J Urol. 198(1):12-21, 2017
                                                                                                  7. Winters BR et al: Cystic renal cell carcinoma carries an excellent prognosis regardless of tumor size. Urol Oncol. 33(12):505.e9-13, 2015