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
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
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
Silverman SG et al: Bosniak classification of cystic renal masses, version 2019: an update proposal and needs assessment. Radiology. 292(2):475-88, 2019
Dillman JR et al: Hereditary renal cystic disorders: imaging of the kidneys and beyond. Radiographics. 37(3):924-6, 2017
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
Schoots IG et al: Bosniak classification for complex renal cysts reevaluated: a systematic review. J Urol. 198(1):12-21, 2017
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 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
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
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
Silverman SG et al: Bosniak classification of cystic renal masses, version 2019: an update proposal and needs assessment. Radiology. 292(2):475-88, 2019
Dillman JR et al: Hereditary renal cystic disorders: imaging of the kidneys and beyond. Radiographics. 37(3):924-6, 2017
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
Schoots IG et al: Bosniak classification for complex renal cysts reevaluated: a systematic review. J Urol. 198(1):12-21, 2017
Winters BR et al: Cystic renal cell carcinoma carries an excellent prognosis regardless of tumor size. Urol Oncol. 33(12):505.e9-13, 2015
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