Jean Michel Correas, small renal tumors multiparametric characterization is there a remaining place for biopsy, jfim ifupi milan 2018

1. jean-michel.correas@nck.aphp.fr
Pr JM Correas MD PhD & Pr O Hélénon
Paris-Descartes University & Department of Adult Radiology, Necker University Hospital
Ecole Supérieure de Physique et Chimie Industrielles, Paris Tech,
Institut Langevin (CNRS UMR 7587) & INSERM ERL 979
Paris France
Small renal tumors multiparametric characterization:
is there a remaining place for biopsy?
1st Italian-French Update Imaging – IFUPI
Advanced Multiparametric Imaging - How to use in daily practice
MILAN March 23-24 2018
www.jfim.org

2. Conflict of Interest:
- Toshiba MS: expert and lecturer
- Philips US: expert and lecturer
- SuperSonic Imagine: expert and lecturer
- Hitachi MS: expert and lecturer
- Bracco SA: expert and lecturer, principal investigator of
BR1-127 and SonoCap protocol
- Guerbet SA: expert and lecturer, principal investigator of
NsSafe and Secure protocol, lecturer
jean-michel.correas@aphp.fr

3. ● Increasing use of abdominal US, CT and MRI
=> Increased incidental SMR detection (+ 3.7% per year)
=> Increased incidence of CKD (30% elderly population)
=> Development of partial nephrectomy/ tumorectomy
● Some renal masses remain indeterminate:
- Renal masses that are not categorizable
- Cystic masses of classe III & IIF (Bosniak scheme)
- Solid tumors without intra tumoural fat
“How to deal with small indeterminate renal masses”
=> a very common situation
Introduction

4. Small indeterminate RMs
Definition
• The “small” RM
Defined as mass ≤ 3cm in diameter/ < 4cm
Very small mass ≤ 8mm
• The indeterminate RM
One that cannot be:
- characterized as cystic or solid
- diagnosed as benign or malignant

5. Characterization of RMs
Imaging Work-up
• STEP 1: separate cystic from solid
By differentiating non enhancing fluid filled
mass from enhancing soft tissue
Demonstration post-contrast enhancement
=> A threshold of +20 HU indicates
definitive enhancement
=> Lack of enhancement < +10 HU

6. Characterization of RMs
Imaging Work-up
• STEP 2: “Cystic RM”
=> Bosniak classification system
With exception of thickened wall cystic RMs
that need specific workup:
- Originating from urinary tract (diverticula, calix)
- Resulting from infection or hemorrhage
(with exception of localized cystic disease)

7. Characterization of RMs
Imaging Work-up
• STEP 2: “Solid enhancing RM”
One pseudotumours are excluded:
including prominent Bertin column, dysmorphism,
hypertrophied parenchyma adjacent to scar,
inflammatory RMs (focal PN)
=> Differentiate AGML with fat from
tumors at risk of RCC

8. Imaging techniques
Ultrasound
• Conventional US (THI and compounding techniques)
- Provides definitive diagnosis in most simple cysts
- RMs that do not fit criteria are indeterminate
and require additional imaging evaluation (CT…)
• Contrast-enhanced US
- High Se demonstrating tissue vascularity
- Excellent NPV that can help rule out malignancy
Limits: Risk of over-classification of septated cysts

10. Imaging techniques: CT
• Gold standard
- Appropriate dedicated technique
- Limitations:
Pseudo-enhancement (volume averaging, artifacts)
Suboptimal contrast resolution
• Technique: CE-CT
pre and post contrast 3/4 phases
slice thickness ≈ 1.2-3 mm
high resolution 0.6-1.2 mm
Detection of fat +++

11. Imaging techniques:
MRI
• Alternative imaging technique
- Problem-solving modality in RMs
that remain equivocal
- Advantages over CT:
Higher contrast-resolution and Se to contrast enhancem.
Characterization of blood breakdown and necrosis
• Technique: CE-MRI
- T2w fat sat seq., Diffusion imaging, T1w in-out phase
- T1w-fat sat DCE with pre post contrast 4/5 phases 8 min
- BUT higher rate of technically limited exams
Fluid-iron level

12. How to deal with
Very small RMs
• Very small RMs that are not
categorizable
because of volume averaging
- In general population
likely to be microcyst
=> STOP (no further imaging)*
- In population at risk of RC: Hereditary RCC sd
History or synchronous RCC
=> Watchfull waiting
MRI in selected cases (T2w FS and DwI)
* Bosniak MA Radiology 1991 ; Curry NS AJR 1995

13. DW imaging in combination with T2w increases confidence in differentiating
very small cystic from solid masses
Roy C et al. Diffusion-weighted MR imaging of the kidney J Radiol 2010
Taouli B et al. Diffusion-W MR Imaging for characterization of renal lesions: comparison with
contrast-enhanced MRI Radiology 2009

14. How to deal vvwith
Small RMs
• Small RMs that are not categorizable
because of equivocal attenuation characteristics
- Equivocal « enhancement »
Post-contrast change in HU: >+10 <+20 HU
- Indeterminate attenuation values
Pre-contrast HU between 15 and 50 HU
- Both equivocal characteristics
• Differential diagnosis
- Pseudo-enhancement (beam hardening artifact)
- Atypical hyperdense cyst (attenuation <50HU)
- Papillary RCC with poor vascularity (17% <+15U)*
Maximum
enhancement
Nephrographic phase
6%
Couvidat C, Eiss D, Merran S, Vieillefond A, Correas JM, Hélénon O.
Papillary renal cell carcinoma: spectrum of imaging findings with pathologic correlation J Radiol (in press)

15. How to deal with
Small RMs not categorizable
• Equivocal “enhancement”
- Cyst + Beam hardening artifact *
Likely to be cystic + pseudo-enhancement
When small (<30 mm) endophytic
+ water attenuating (≤15 HU pre INJ)
=> Ultrasound
± CEUS * Coulam, AJR 2000
Heneghan, JCAT 2002
Birnbaum, Radiology 2002
31 HU
(+19HU)
12 HU

16. How to deal with
Small RMs not categorizable
• Indeterminate attenuation values (20 – 50 HU)
with no significant enhancement (<+10 HU)
- Atypical hyperdense cyst vs papillary RCC
=> Ultrasound first ± contrast-enhanced US
=> / MRI when US fails demonstrate typical cyst

17. History of partial nephrectomy
for papillary RCC of the left kidney

18. Indeterminate attenuation values (20-50HU)
Atypical hyperdense cyst?
Hypovascular RCC
Pre-contrast: 40 HU
Post-contrast: 49 HU

19. Indeterminate contrast enhancement
Atypical hyperdense cyst?
Hypovascular RCC

20. Equivocal « enhancement » (+10-20HU)
Hyperdense cyst + pseudo-enhancement?
RCC with internal hemorrhage?
68 HU 85HU (+17)

21. How to deal with
Indeterminate cystic RMs
• Bosniak renal cyst classification
- System that suggests clinical management
scheme based on CT findings
- Among the 5 categories:
3 are definitely benign (I, II) or malignant (IV)
IIF & III are indeterminate (benign/malignant)
Curry N AJR 2000
Israel GM, Bosniak MA AJR 2003
Bosniak MA Radiology 1986
Bosniak MA Radiology 1997

22. Indeterminate Cat IIF (5% are malignant)
=> follow-up imaging (5 years)
to demonstrate stability vs progression
Multiple septae (>2)
or minimal wall thickening
Hair-line thin
«Perceived» enhancement
Thick irregular calcification
+ Lack of enhancement

23. Indeterminate Cat IIF
MRI can lead to upgrade complex cysts: 10%
From cat IIF to III (3/7 cases)
Increased thickness of septa or wall
Affects patient management
Outcome: 1 case malignant
Increase rate of malignancy
Indeterminate CT Cat IIF
=> MRI first
CT IIF / MR III => Surgery
CT IIF + MR IIF => follow-up Israel GM, Hindman N, Bosniak MA
Evaluation of cystic renal masses:
comparison of CT and MRI by using the Bosniak classification system. Radiology 2004

24. Cat. IIF Cat. III

25. Indeterminate Cat III (malignancy: 50-60%)
=> require surgery in most cases
Grossely thickened wall
Unequivocal enhancement
Wall thickening
Uniform smooth
or slightly irregular
Unequivocal enhancement
Multiloculated
Numerous grossly
Thickened septae and wall
Unequivocal enhancement

26. Indeterminate Cat III
Equivocal wall enhancement
●“Cat III” with equivocal
wall enhancement at CT
=> CE-MRI
Obvious contrast uptake leads to
definitive surgical category III

27. How to deal with
Small indeterminate solid RMs
• Solitary solid renal neoplasms
- Benign AGML should be first excluded
Intratumoral fat (≤20 HU) without calcification
- Among non fat-containing small indeterminate
neoplasms most are RCCs, 25% are benign*
mainly: oncocytomas and AGML with minimal
fat that are indistinguishable from a small RCC
* Frank I et al Solid renal tumors an analysis of
pathological features related to tumor size J Urol 2003

28. How to deal with
Small indeterminate solid RMs
• MRI characterization: combination of criteria
1- T2W HIGH
CCC/Oncocytoma
MID
Chromophobic
LOW
AML / PapT
2- IP/OP
Signal Drop
YES
CCC / PapT / AML
NO
Any
3- DWI HIGH
Oncocytoma/CCC
MID
Chromophobic
LOW
AML / PapT
4- WASH-IN FAST
CCC / AML
MID
Chromophobic/
Oncocytoma
SLOW
PapT
5- WASH-OUT YES
CCC / AML
MID
Chromophobic/
Oncocytoma
NO
PapT
Cornelis F et al. Seminar US, CT, MRI 2016

29. Chromophobic carcinoma
T1w IN T1w OPPT2w ADC
DCE
26 YO woman Courtesy Pr Cornelis & Pr Grenier

30. Percutaneous biopsy
• To date only option to
differentiate confidently:
- low fat benign RM from malignant RM
- RCC from metastasis or lymphoma
- RCC sub-types
• Failure rate: 3-9%
(including inconclusive)
• Accuracy: benign/malignant tissue 92%
Subtype 92% Führman grade 70%
• Serious adverse events: (hemorrhagic) <1%
Millet I et al. Characterization of Small Solid Renal Lesions:
Can Benign and Malignant Tumors Be Differentiated With CT? AJR 2011
Schmidbauer J et Al. Diagnostic accuracy of CT-guided percutaneous biopsy of renal masses. Eur Urol
2007

31. Percutaneous biopsy of solid RMs
• When definite diagnosis of malignancy is needed
before treatment decision & planning especially in:
- high-risk surgical candidates
- limited functional renal reserve
- central tumor (high risk of nephrectomy)
- before percutaneous ablative treatment
=> Help decide active surveillance
in selected cases
Neuzillet Y et al. Follow-up of renal oncocytoma diagnosed by percutaneous tumor biopsy Urology 2005
Silverman SG et Al. Renal masses in the adult patient: the role of percutaneous biopsy. Radiology 2006
Schmidbauer J et Al. Diagnostic accuracy of CT-guided percutaneous biopsy of renal masses. Eur Urol 2007

32. 52 year-old man, history of renal cysts
- Acute back pain
- CE-CT and CE-MRI
=> hemorrhagic cyst

33. Conclusion
• RM characterization: multimodality & multiparametric imaging
• CT gold standard/ CEUS + MRI major role (cystic/necrotic RMs)
• Masses that remain indeterminate at CT
=> Very small lesions require MRI in selected cases
=> Small indeterminate masses with equivocal attenution values
=> CEUS first / MRI
• Misclassified cystic renal masses
=> Cat IIF that can be underclassified at CT
=> MR in select cases prior Bosniak staging
• Indeterminate low fat/ homogeneous tumors
=> Biopsy in selected cases to help decision-making
=> When patient management could be changed