# Bosniak — Bosniak classification of cystic renal masses, version 2019

> Classification of cystic renal masses into classes by likelihood of malignancy.

**Situação:** vigente · **Órgão:** Rim · **Órgão emissor:** Radiology consensus (Silverman et al.) · **Versão:** 2019 · **Ano:** 2019

## Procedência e vigência
- Família: léxico
- Tipo de lógica: flat
- Modalidade: CT, MRI
- Fonte primária: Silverman SG, Pedrosa I, Ellis JH, et al.. Bosniak Classification of Cystic Renal Masses, Version 2019: An Update Proposal and Needs Assessment (2019) — https://doi.org/10.1148/radiol.2019182646
- Última verificação: 2026-06-26
- Última checagem: 2026-06-26

## Categorias

| Código | Rótulo | Critérios | Conduta | Risco | Localizador | Verificado |
| --- | --- | --- | --- | --- | --- | --- |
| I | Class I | Well-defined cystic mass with a thin (2 mm or less) smooth wall that may enhance; homogeneous simple-fluid attenuation (about -9 to 20 HU on CT); no septa, no calcification, and no nodules. | No imaging follow-up indicated; may be described simply as a cyst. | Considered universally benign (essentially 0% malignancy). | Silverman et al., Radiology 2019 (PMC6677285), CT/MRI criteria Table 2; corroborated radiologyassistant.nl Bozniak-2019 section 'Bosniak I' | ✓ |
| II | Class II | Cystic masses with a thin (2 mm or less) smooth wall and few (1-3) thin (2 mm or less) septa, where wall and septa may enhance and calcification of any type is allowed; also includes several homogeneous categories such as masses about -9 to 20 HU, homogeneous hyperattenuating masses 70 HU or greater at noncontrast CT, homogeneous nonenhancing masses above 20 HU at renal-mass-protocol CT, and homogeneous masses about 21-30 HU at portal venous phase. | No follow-up indicated for typical cases; treated as benign. | Reported malignancy rate is below 1% (may be as low as 0%). | Silverman et al., Radiology 2019 (PMC6677285), CT/MRI criteria Table 2; corroborated radiologyassistant.nl Bozniak-2019 section 'Bosniak II' | ✓ |
| IIF | Class IIF | Cystic masses with a smooth, minimally thickened (3 mm) enhancing wall, or smooth minimal (3 mm) thickening of one or more enhancing septa, or many (4 or more) smooth thin (2 mm or less) enhancing septa. | Imaging surveillance (follow-up) is recommended; observation is considered safe over a roughly 5-year period. | Reported malignancy rates are wide, in the range of 0% to 38%; the article notes that of 954 stable IIF masses only 54 were resected, of which 9 (about 17%) were malignant, while about 94% (900 of 954) were not resected and did not progress. | Silverman et al., Radiology 2019 (PMC6677285), CT/MRI criteria Table 2 and accompanying note; corroborated radiologyassistant.nl Bozniak-2019 section 'Bosniak IIF' | ✓ |
| III | Class III | Cystic masses with one or more enhancing thick (4 mm or greater in width) or enhancing irregular (3 mm or smaller obtusely-margined convex protrusions) walls or septa. | Management varies between institutions, with resection/ablation historically standard and active surveillance increasingly advocated; choice depends on lesion size, patient comorbidities, and surgeon preference. | Indeterminate; approximately half of resected Bosniak III masses are malignant, with individual series ranging from about 25% to 100% (conversely about half are benign). | Silverman et al., Radiology 2019 (PMC6677285), CT/MRI criteria Table 2; irregular definition Table 3; corroborated radiologyassistant.nl Bozniak-2019 section 'Bosniak III' | ✓ |
| IV | Class IV | Cystic masses with one or more enhancing nodules, defined as a focal enhancing convex protrusion of any size with acute margins, or a 4 mm or larger convex protrusion with obtuse margins relative to the wall or a septum. | Treatment (resection or ablation) is recommended in most cases when patient characteristics allow; observation is discussed only for selected patients. | Approximately 90% malignant, with individual series ranging from about 56% to 100% (a minority are benign). | Silverman et al., Radiology 2019 (PMC6677285), CT/MRI criteria Table 2; nodule definition Table 3; corroborated radiologyassistant.nl Bozniak-2019 section 'Bosniak IV' | ✓ |

### Citações por categoria
- **I**: Silverman SG, Pedrosa I, Ellis JH, et al.. Bosniak Classification of Cystic Renal Masses, Version 2019: An Update Proposal and Needs Assessment (2019) — https://doi.org/10.1148/radiol.2019182646 · Silverman et al., Radiology 2019 (PMC6677285), CT/MRI criteria Table 2; corroborated radiologyassistant.nl Bozniak-2019 section 'Bosniak I'
- **II**: Silverman SG, Pedrosa I, Ellis JH, et al.. Bosniak Classification of Cystic Renal Masses, Version 2019: An Update Proposal and Needs Assessment (2019) — https://doi.org/10.1148/radiol.2019182646 · Silverman et al., Radiology 2019 (PMC6677285), CT/MRI criteria Table 2; corroborated radiologyassistant.nl Bozniak-2019 section 'Bosniak II'
- **IIF**: Silverman SG, Pedrosa I, Ellis JH, et al.. Bosniak Classification of Cystic Renal Masses, Version 2019: An Update Proposal and Needs Assessment (2019) — https://doi.org/10.1148/radiol.2019182646 · Silverman et al., Radiology 2019 (PMC6677285), CT/MRI criteria Table 2 and accompanying note; corroborated radiologyassistant.nl Bozniak-2019 section 'Bosniak IIF'
- **III**: Silverman SG, Pedrosa I, Ellis JH, et al.. Bosniak Classification of Cystic Renal Masses, Version 2019: An Update Proposal and Needs Assessment (2019) — https://doi.org/10.1148/radiol.2019182646 · Silverman et al., Radiology 2019 (PMC6677285), CT/MRI criteria Table 2; irregular definition Table 3; corroborated radiologyassistant.nl Bozniak-2019 section 'Bosniak III'
- **IV**: Silverman SG, Pedrosa I, Ellis JH, et al.. Bosniak Classification of Cystic Renal Masses, Version 2019: An Update Proposal and Needs Assessment (2019) — https://doi.org/10.1148/radiol.2019182646 · Silverman et al., Radiology 2019 (PMC6677285), CT/MRI criteria Table 2; nodule definition Table 3; corroborated radiologyassistant.nl Bozniak-2019 section 'Bosniak IV'

## Histórico de versões

| Data | Evento | Detalhe | Situação |
| --- | --- | --- | --- |
| 2019-05-01 | revised | Bosniak version 2019 update proposal published. | confirmed |


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> Conteúdo de referência reescrito. Confira a publicação primária vigente. Não é dispositivo médico nem substitui o julgamento clínico. O radiologista responsável pelo laudo permanece o autor e o responsável.

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