Bosniak classification system of renal cystic masses (version 2005)
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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.
Usage
The proposedBosniak classification is widely used by radiologists and urologists for addressing the clinical problem assessing renal cysts 3. It was last updated in 2005 12. A Bosniak classification, version 2019 11 does has been proposed to increase the accuracy and include MRI features but does not yet (c. 2021) have widespread validation (c. 2021).
Classification
Bosniak I
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benign simple cyst
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thin ("hairlinehairline-thin" or "pencil-thin")wall of2mm or less≤2 mm - water
attenuationdensity - no septa, calcifications, or solid components
- no enhancement
- work-up: none
- percentage malignant: ~0%ref
-
Bosniak II
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minimallybenign cyst - "minimally complex"-
a fewfew hairline thin <1 mm septa or thin calcifications (thickness not measurable); - perceived enhancement
- non-enhancing high-attenuation (due to proteinaceous or haemorrhagic contents) renal lesions <3 cm
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these lesions aregenerally well marginated - work-up: none
- percentage malignant: ~0%ref
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Bosniak IIF
- minimally complex
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increased numbermultiple hairline thin septa or minimally smooth thickened walls or septa -
perceived but no measurable enhancement of
septa, minimally thickened with nodularwall orthick calcificationssepta -
therecalcification can be present and may beperceived (but not measurable) enhancement of hairline-thin smooth septathick and nodular -
minimal thickening of the wall with perceivable enhancementgenerally well marginated -
hyperdense cysthigh-attenuation lesion >3 cm diameter,mostlytotally intrarenal(less than 25(<25% of wall visible); no enhancement - requiring follow-up
(the 'F' in 2F is(F for'follow'follow-up): needs ultrasound/CT/MRI follow up - no strict rules on the time frame but reasonable at 6 months, 12 months then annually for 5 years 3 - percentage malignant: ~5% 6
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Bosniak III
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indeterminateindeterminate cystic mass-
thick, nodular multiple septathickened irregular orwallsmooth walls or septa with measurable enhancement - treatment/work-up: partial nephrectomy or radiofrequency ablation in
elderly orpoor surgical candidatesref - percentage malignant: ~55% 6
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Bosniak IV
- clearly malignant cystic mass
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solid mass with a large cysticBosniak III criteria + enhancing soft tissue components adjacent to but independent of wall ora necrotic componentseptum - treatment: partial or total nephrectomy
- percentage malignant: ~100%ref
-
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.
-<p>The <strong>Bosniak classification system of renal cystic masses</strong> 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.</p><p>The proposed <a href="/articles/bosniak-classification-of-cystic-renal-masses-version-2019">Bosniak classification, version 2019</a> <sup>11</sup> does not yet have widespread validation (c. 2021).</p><h4>Classification</h4><h6>Bosniak I</h6><ul><li>simple cyst<ul>-<li>thin ("hairline-thin" or "pencil-thin") wall of 2mm or less</li>-<li>water attenuation</li>- +<p>The <strong>Bosniak classification system of renal cystic masses</strong> 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.</p><h4>Usage</h4><p>The Bosniak classification is widely used by radiologists and urologists for addressing the clinical problem assessing renal cysts <sup>3</sup><span style="font-size:10.8333px">.</span> It was last updated in 2005 <sup>12</sup>. A <a href="/articles/bosniak-classification-of-cystic-renal-masses-version-2019">Bosniak classification, version 2019</a> <sup>11</sup> has been proposed to increase the accuracy and include MRI features but does not yet (c. 2021) have widespread validation.</p><h4>Classification</h4><h6>Bosniak I</h6><ul><li>benign simple cyst<ul>
- +<li>hairline-thin wall of ≤2 mm</li>
- +<li>water density</li>
- +<li>no enhancement</li>
-<li>percentage malignant: ~0%</li>- +<li>percentage malignant: ~0% <sup>ref</sup>
- +</li>
-</li></ul><h6>Bosniak II</h6><ul><li>minimally complex<ul>-<li>a few thin <1 mm septa or thin calcifications (thickness not measurable); </li>- +</li></ul><h6>Bosniak II</h6><ul><li>benign cyst - "minimally complex"<ul>
- +<li>few hairline thin <1 mm septa or thin calcifications (thickness not measurable)</li>
- +<li>perceived enhancement</li>
-<li>these lesions are generally well marginated</li>- +<li>generally well marginated</li>
-<li>percentage malignant: ~0%</li>- +<li>percentage malignant: ~0% <sup>ref</sup>
- +</li>
-<li>increased number of septa, minimally thickened with nodular or thick calcifications</li>-<li>there may be perceived (but not measurable) enhancement of hairline-thin smooth septa</li>-<li>minimal thickening of the wall with perceivable enhancement</li>-<li>hyperdense cyst >3 cm diameter, mostly intrarenal (less than 25% of wall visible); no enhancement</li>-<li>requiring follow-up (the 'F' in 2F is for 'follow'): needs ultrasound/CT/MRI follow up - no strict rules on the time frame but reasonable at 6 months</li>- +<li>multiple hairline thin septa or minimally smooth thickened walls or septa</li>
- +<li>perceived but no measurable enhancement of wall or septa</li>
- +<li>calcification can be present and may be thick and nodular</li>
- +<li>generally well marginated</li>
- +<li>high-attenuation lesion >3 cm diameter, totally intrarenal (<25% of wall visible); no enhancement</li>
- +<li>requiring follow-up (F for follow-up): needs ultrasound/CT/MRI follow up - no strict rules on the time frame but reasonable at 6 months, 12 months then annually for 5 years <sup>3</sup>
- +</li>
-</li></ul><h6>Bosniak III</h6><ul><li>indeterminate<ul>-<li>thick, nodular multiple septa or wall with measurable enhancement</li>-<li>treatment/work-up: partial nephrectomy or <a href="/articles/radiofrequency-ablation">radiofrequency ablation</a> in elderly or poor surgical candidates</li>- +</li></ul><h6>Bosniak III</h6><ul><li> indeterminate cystic mass<ul>
- +<li>thickened irregular or smooth walls or septa with measurable enhancement</li>
- +<li>treatment/work-up: partial nephrectomy or <a href="/articles/radiofrequency-ablation">radiofrequency ablation</a> in poor surgical candidates <sup>ref</sup>
- +</li>
-</li></ul><h6>Bosniak IV</h6><ul><li>clearly malignant<ul>-<li>solid mass with a large cystic or a necrotic component</li>- +</li></ul><h6>Bosniak IV</h6><ul><li>clearly malignant cystic mass<ul>
- +<li>Bosniak III criteria + enhancing soft tissue components adjacent to but independent of wall or septum</li>
-<li>percentage malignant: ~100%</li>- +<li>percentage malignant: ~100% <sup>ref</sup>
- +</li>
References changed:
- 12. Israel G & Bosniak M. An Update of the Bosniak Renal Cyst Classification System. Urology. 2005;66(3):484-8. <a href="https://doi.org/10.1016/j.urology.2005.04.003">doi:10.1016/j.urology.2005.04.003</a> - <a href="https://www.ncbi.nlm.nih.gov/pubmed/16140062">Pubmed</a>
Tags changed:
- bosniak
- bosniak classification
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