Bosniak classification system of renal cystic masses (version 2005)

Changed by Daniel J Bell, 16 Nov 2017
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The Bosniak classification system of renal cystic masses divides renal cystic masses into five categories based on imaging characteristics on contrast-enhanced CT. It is helpful in predicting a risk of malignancy and suggesting either follow up or treatment.

Classification

Bosniak 1
  • simple cyst
    • imperceptible wall, rounded
    • work-up: nil
    • percentage malignant: ~0%
Bosniak 2
  • minimally complex
    • a few thin <1 mm septa or thin calcifications (thickness not measurable); non-enhancing high-attenuation (due to proteinaceous or haemorrhagic contents) renal lesions of less than 3 cm are also included in this category; these lesions are generally well marginated
    • work-up: nil
    • percentage malignant: ~0%
Bosniak 2F
  • minimally complex
    • increased number of septa, minimally thickened with nodular or thick calcifications
    • there may be perceived (but not measurable) enhancement of a hairline-thin smooth septa
    • hyperdense cyst >3 cm diameter, mostly intrarenal (less than 25% of wall visible); no enhancement
    • requiring follow-up: needs ultrasound/CT follow up - no strict rules on the time frame but reasonable at 6 months
    • percentage malignant: ~ 5% 6
Bosniak 3
  • indeterminate
    • thick, nodular multiple septa or wall with measurable enhancement, hyperdense on CT (see 2F)
    • treatment/work-up: partial nephrectomy or radiofrequency ablation in elderly or poor surgical candidates
    • percentage malignant: ~55% 6
Bosniak 4
  • clearly malignant
    • solid mass with a large cystic or a necrotic component
    • treatment: partial or total nephrectomy
    • percentage malignant: ~100%

History and etymology

It is named after Morton A. Bosniak (1929-2016), who was professor emeritus in radiology at New York University (NYU) Langone School of Medicine 9,10.

  • -</li></ul><h4>History and etymology</h4><p>It is named after <strong>Morton A. Bosniak </strong><sup>9</sup></p>
  • +</li></ul><h4>History and etymology</h4><p>It is named after <strong>Morton A. Bosniak</strong> (1929-2016), who was professor emeritus in radiology at New York University (NYU) Langone School of Medicine <sup>9,10</sup>.</p>

References changed:

  • 10. Megibow AJ, Israel GM. Morton A. Bosniak, MD. Radiology. 282 (2): 616. <a href="https://doi.org/10.1148/radiol.2016164037">doi:10.1148/radiol.2016164037</a> - <a href="https://www.ncbi.nlm.nih.gov/pubmed/28099104">Pubmed</a> <span class="ref_v4"></span>

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