IMAGING OF BENIGN RENAL MASSES. Dr. Darragh Halpenny NYU Langone Medical Center New York

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1 IMAGING OF BENIGN RENAL MASSES Dr. Darragh Halpenny NYU Langone Medical Center New York

2 Dr. Andrew Rosenkrantz Dr. Mark Page

3 Overview of the common benign renal masses and their imaging features Briefly discuss some rarer benign renal masses Discuss common mimics of renal mass lesions and potential pitfalls in renal mass imaging

4 Role of the radiologist in the management of small renal masses Attention on the incidental renal mass

5 Over riding clinical questions: Can we make a definitive diagnosis? Could we to follow it up? Does the lesion need intervention?

6 Prasad et al. AJR 2008; 190:

7 BENIGN RENAL MASS Solid mass Cystic mass With fat Angiomyolipoma Without fat Oncocytoma Lipid poor AML Leiomyoma Haemangioma Reninoma Renal cyst Cystic nephroma Lymphangioma Mixed epithelial and stromal tumor

8 ONCOCYTOMA

9 ONCOCYTOMA 5% of solid renal lesions 13% of resected renal lesions are benign almost all are oncocytoma or AML Peak age of incidence is in the seventh decade Men > women

10 ONCOCYTOMA If bilateral or multicentric consider hereditary syndromes Renal oncocytosis Birt-Hogg-Dubé syndrome Main clinical issues Indistinguishable from renal cell carcinomas on imaging alone May be associated with RCCs either as hybrid tumors or as collision tumors

11 ONCOCYTOMA Renal cortical tumors Solitary Well-demarcated Unencapsulated (pseudocapsule - rim of compressed normal renal parenchyma)

12 ONCOCYTOMA - CT Non contrast < 3 cm - homogenous attenuation > 3 cm - heterogenous attenuation Post contrast Small tumors may enhance homogeneously Larger masses heterogenous enhancement

13 ONCOCYTOMA Characteristic central stellate fibrotic scar Seen in 1/3rd More often with large tumors Hemorrhage in up to 20% of cases

14 ONCOCYTOMA - MRI Relative to the renal cortex T1-weighted most are hypointense T2-weighted most are hyperintense

15 ONCOCYTOMA - MRI Central scar (when present) Low signal intensity on T1 Variable signal intensity on T2 May show delayed enhancement

16 Oncocytoma CT Chromophobe T1 T2 Gd +

17 ONCOCYTOMA DWI Lassel EA et al Eur Radiol 2014 Meta-analysis based on 17 studies with 764 patients Significant difference between ADC values of renal cell carcinomas and oncocytomas

18 Managed surgically

19 ANGIOMYOLIPOMA

20 BACKGROUND Angiomyolipoma is the most common benign renal tumor Variable amounts of muscle, fat and vascular tissue 80% sporadic Remainder associated with tuberous sclerosis

21 BACKGROUND Most commonly an incidental finding Over 4cm: Symptoms develop in up to 80% Most commonly haemorrhage

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23 CT Classical finding is a fat containing mass RCCs containing macroscopic fat extremely rare Small subset (<5%) which do not contain macroscopic fat

24 CT Differentiate AML from the very rare retroperitoneal liposarcoma AML Renal origin Defect in the renal parenchyma Liposarcoma Smooth interface Displace and compress kidney Yeh et al J Computed Assist Tomography 2008

25 Yeh et al J Computed Assist Tomography 2008

26 MRI For classic AML

27 T1 with and without fat suppression

28 India ink artifact

29 MINIMAL FAT AML Account for 6% of surgically excised small renal masses No macroscopic fat 3% 10% of fat at histology

30 MINIMAL FAT AML IMAGING FEATURES Non contrast homogenously hyper-attenuating Enhance mild - moderately Quite different to Clear Cell RCC But very similar to papillary RCC T2 Hypointense Kim J et al. Radiology 2009 Aug;252(2):441-8

31 MANAGEMENT Macroscopic fat < 4 cm Observe Consider US every 12 months Consider intervention if > 4cm Symptomatic Large aneurysms Surgery or embolization If no macroscopic fat - diagnostic dilemma - surgery

32 ADDITIONAL BENIGN RENAL MASSES Very rare Most are asymptomatic Most managed surgically as they are indistinguishable from RCC Most common symptoms flank pain abdominal mass hematuria

33 METANEPHRIC ADENOMA Peak incidence in the sixth decade Well-defined solid mass CT Non-contrast Hyper-attenuating Post contrast Minimal enhancement

34 METANEPHRIC ADENOMA MRI Hypointense/Isointense on T1 Heterogenous on T2 Hypovascular

35 LEIOMYOMA Smooth muscle of the capsule - peripheral Buckling of the cortex CT Non- contrast hyperattenuating solid mass MR T1 and T2 hypointense Mild homogenous enhancement

36 PAPILLARY ADENOMA Most common renal epithelial neoplasm Approximately 40% of patients >70 years Common in patients with acquired renal cystic disease long-term hemodialysis patients Extremely small (< 5 mm) Cannot be distinguished from other tumors on imaging

37 RENAL HEMANGIOMA Rare mesenchymal neoplasm 1 in 2000 to 1 in 30,000 individuals Young adults Can be associated with Sturge-Weber and Klippel-Trénaunay

38 RENAL HEMANGIOMA 90% arise from the renal pyramids or the pelvis CT Noncontrast lobulated isoattenuating mass phleboliths uncommon Post contrast early, intense persistent enhancement Venkata S. RadioGraphics 2010, 30,

39 RENAL HEMANGIOMA MRI T1 hypointense T2 hyperintense Can mimic a complex cyst with enhancing solid components Venkata S. RadioGraphics 2010, 30,

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41 CYSTIC NEPHROMA Cystic lesion Predominantly perimenopausal women Benign but sarcomatous degeneration has been described

42 CYSTIC NEPHROMA CT Well-demarcated, multilocular cystic lesion with thin septations Enhancing septations Usually without solid components

43 CYSTIC NEPHROMA MRI T2 T1 Gd+ Capsule and septa are hypointense Cystic locules hyperintense Cystic locules may have varying appearance (presence proteins/blood) Septations enhance

44 CYSTIC NEPHROMA Fall under Bosniack category 3 cyst Mimics cystic renal cell carcinoma Managed surgically in the majority of cases

45 CYSTIC NEPHROMA V MIXED EPITHELIAL AND STROMAL TUMOR Very similar clinical and radiological appearance MEST may have more solid components

46 LYMPHANGIOMA Multilocular cystic mass Perinephric or renal sinus region typical Involvement of both kidneys not uncommon Dilated retroperitoneal lymphatics Prasad et al. AJR.2008

47 LYMPHANGIOMA MR T1 hypointense T2 hyperintense Signal intensity of the intracystic fluid may be variable, depending on the presence of hemorrhage/debris/protein Venkata S. RadioGraphics 2010, 30,

48 RENINOMA Juxtaglomerular cell neoplasm Secretes renin Young adults Triad of poorly controlled hypertension hypokalemia high plasma renin activity Typically well-circumscribed cortical tumor Hypovascular on arterial phase - possibly because of renin-induced vasoconstriction

49 MANAGEMENT OF INCIDENTAL MASS

50 INCIDENTAL MASS Establish that the lesion is indeed a mass Mass should demonstrate Tissue with HU > 20 Enhance >20 HU between non contrast and post contrast (beware pseudo-enhancement) >15 HU is equivocal HU measurement can be unreliable

51 INCIDENTAL MASS If difficulty demonstrating enhancement on CT, consider MRI Image subtraction is a useful tool

52 MIMICS OF A NEOPLASM

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64 Fever Leukcytosis Flank pain

65 Other potential mimics include Renal trauma Renal infarction

66 INCIDENTAL RENAL MASS One you have established a true mass is present..

67 INCIDENTAL RENAL MASS Characterize the lesion Identify features that predict benignity

68 INCIDENTAL SOLID RENAL MASS Aside from fat, no single feature predicts benignity Some features should be looked for, but are not specific E.G. Small, hyper-attenuating, homogeneously enhancing, T2 hypointense mass Kim J et al. Radiology 2009 Aug;252(2):441-8

69 INCIDENTAL RENAL MASS Consider management options Do nothing Observe Percutaneous biopsy Surgery/Ablation

70 IMPORTANT CONSIDERATIONS If there is a history of primary extra-renal neoplasm 50% 85% of solitary renal masses are metastatic If multiple solid masses consider multifocal renal cell carcinoma Consider biopsy multiple oncocytomas Can be syndromic lymphoma (but rarely presents only in the kidney)

71 Remainder of the approach to a solid renal mass is largely based on size Most important predictor of aggressive behavior

72 SIZE 13% of all resected solid renal masses are benign However < 3cm 25% benign < 2 cm 30% benign < 1 cm 44% benign Is there an alternative strategy for small solid renal lesions?

73 Incidental solid mass on CT <1 cm 1 3 cm > 3 cm Follow up at months - 12 months - Then yearly If becomes >1cm Hyper-attenuating, homogeneously enhancing Surgery Surgery Consider MRI or biopsy J Am Coll Radiol 2010;7:

74 INCIDENTAL CYSTIC MASS Follows Bosniak categorization In general, size is not a factor

75 Bosniak I + II Bosniak IIF Bosniak III + IV

76 Incidental cystic mass on CT Bosniak I + II Bosniak IIF Bosniak III + IV Benign No follow-up CT/MRI at 6 months 12 months 5 Years Surgery No change = benign Morphologic change Surgery

77 ACTIVE SURVEILLANCE Initially observe selected patients Intervene when specified size or growth rate criteria met When solid lesions undergo active surveillance, approximately 1% will develop metastases Vast majority in lesions which show interval growth Only 1 reported case of 2.4-cm mass progressing to metastases with no increase in tumor size

78 Evidence for active surveillance? Retrospective example Patel et al. BJU 2012 mainly retrospective Delayed Intervention and Surveillance for Small Renal Masses (DISSRM) Register 202 patients with T1a lesions 46 months patients 71 active surveillance 131 surgery 101 active surveillance 226 surgery Median follow-up of 34 months No difference in overall or cancer-specific survival 4 deaths 0 RCC related 4 deaths 1 RCC related Average growth rate = 1mm/year

79 ACTIVE SURVEILLANCE Rate of malignancy in lesions with zero growth is similar to the rate in growing lesions Benign lesions can grow at similar rates to malignant lesions Very rare for lesions without interval growth to metastasize Emerging as an alternate strategy for select patients

80 CONCLUSION Discussed Imaging characteristics of the common benign renal masses Features that can help make a pre operative diagnosis of benignity Mimics of renal mass Management and follow-up of incidentally discovered small renal masses, many of which are benign

81 THANK YOU