The document discusses the differential diagnosis of solid renal masses, emphasizing the importance of considering various conditions such as renal cell carcinoma, angiomyolipoma, lymphoma, and metastases. It highlights key diagnostic features, imaging techniques, and clinical history required to discern among different types of renal tumors. Additionally, it outlines the roles of biopsy and imaging in accurately diagnosing renal masses.

1. SOLID RENAL MASS
Hisham AlKhatib, M.D.
Consultant Radiologist

2. •‫اله‬ ‫وعلى‬ ‫هللا‬ ‫رسول‬ ‫على‬ ‫والسالم‬ ‫والصالة‬ ‫هلل‬ ‫الحمد‬
‫اجمعين‬ ‫م‬ّ‫ل‬‫وس‬ ‫وصحبه‬
•، ‫علما‬ ‫وزدني‬ ‫ينفعني‬ ‫بما‬ ‫وعلمني‬ ‫علمتني‬ ‫بما‬ ‫انفعني‬ ‫اللهم‬
‫الحكيم‬ ‫العليم‬ ‫انك‬
• Praise be to Allah and prayers be upon the
Messenger of Allah and his family and
companions.
• Oh God, give me the benefit of what you
have taught me and teach me what benefits
me.

3. ESSENTIAL INFORMATION

4. Key Differential Diagnosis Issues
• Solid, expansile mass in adult is usually renal cell
carcinoma, unless
– Mass contains fat (probably angiomyolipoma)
– Patient has fever, urosepsis (consider pyelonephritis
and renal abscess)
– Patient is immunocompromised (consider lymphoma,
posttransplant lymphoproliferative disorder)
– Patient has known other primary cancer (consider
metastases)

5. Key Differential Diagnosis Issues
• Role of biopsy is evolving but definitely has role in
diagnosing renal lymphoma and metastases
– Useful in diagnosing oncocytoma, angiomyolipoma
(AML)
– Morphology and immunohistochemical features are
key pathologic findings
– Routinely performed prior to percutaneous ablation: ~
20% of small (< 4 cm) enhancing renal masses are
benign (i.e., non-fat-containing AML, oncocytoma)

6. Key Differential Diagnosis Issues
• Morphology of lesion also aids diagnosis:
“beans” vs. “balls”
– Infiltrating tumor maintains reniform (“bean”)
shape: Consider urothelial carcinoma, collecting
duct carcinoma, medullary carcinoma
– Well-circumscribed (“ball”) tumor: Consider renal
cell carcinoma (RCC) (clear cell, papillary,
chromophobe)

7. Key Differential Diagnosis Issues
• Clinical history is key in diagnosing renal
trauma, infection, metastases, lymphoma
– Not usually helpful in diagnosing primary renal
tumors
• CT or MR evaluation of renal mass must
include nonenhanced and parenchymal phase
images
– Arterial phase good for diagnosing column of
Bertin; pyelographic phase essential for
diagnosing transitional cell cancer

8. DIFFERENTIAL DIAGNOSIS

9. Common Diagnosis
• Renal Cell Carcinoma
• Wilms Tumor (Nephroblastoma)
• Column of Bertin (Mimic)
• Fetal Lobulation
• Pyelonephritis

10. Helpful Clues for Common
Diagnoses

11. Renal Cell Carcinoma
• Usually discovered as incidental finding
– May have hematuria or flank pain

12. Renal Cell Carcinoma
• Variable appearance and histology
– From mostly cystic, to hypovascular (papillary), to
hypervascular (most RCCs)
– Large tumors may have lipoid degeneration,
invade renal sinus perirenal fat, simulate
angiomyolipoma
– Large tumors may also have osseous metaplasia

13. Renal Cell Carcinoma
• Variable appearance and histology (continued)
– Common RCC subtypes (WHO classification): Clear
cell, papillary, chromophobe
– Additional rare, aggressive renal epithelial tumors
may be suggested by central infiltrative growth
pattern (collecting duct, medullary carcinoma)

14. Renal Cell Carcinoma
• Large RCC with predilection for renal vein,
inferior vena cava invasion

19. Wilms Tumor (Nephroblastoma)
• Most common solid renal mass in children
• Highly variable appearance

21. Column of Bertin (Mimic)
• Hypertrophied column of septal cortex that
protrudes into renal sinus
– Usually between upper and middle calyces
• Same enhancement characteristics (and
echogenicity) as renal cortex
• Utilize power (color) Doppler to confirm
similar vascularity of adjacent cortex if
identified at screening ultrasound

23. Fetal Lobulation
• Persistent cortical lobulation, reflecting fetal
renal development as multiple separate lobes
• Enhances like normal cortex and medulla

24. Pyelonephritis
• Severe focal pyelonephritis, renal abscess, or
xanthogranulomatous pyelonephritis may be
indistinguishable from tumor by imaging
alone
• Consider clinical presentation; needle
aspiration and drainage of abscess

26. Less Common Diagnosis
• Hyperdense Renal Cyst (Mimic)
• Angiomyolipoma, Renal
• Renal Oncocytoma
• Metastases and Lymphoma, Renal
• Urothelial Cell Carcinoma
• Pyelonephritis, Xanthogranulomatous
• Renal Trauma
• Aneurysm, Renal Artery (Mimic)
• Arteriovenous Malformation, Renal (Mimic)

27. Helpful Clues for Less Common
Diagnoses

28. Hyperdense Renal Cyst (Mimic)
• High-density (“hyperdense” or “hemorrhagic”) renal
cyst is indistinguishable from tumor on either NECT
or CECT alone
– Cyst will not enhance, while viable tumor almost always
enhances ≥ 20 HU (beware papillary RCC)
– Sonography useful to show sonolucent contents and
acoustic enhancement of hyperdense cyst
– Large cyst with extensive hemorrhage may be impossible
to distinguish from necrotic tumor
– Attenuation > 70 HU at NECT strongly suggests high-
attenuation (“hyperdense”) CT rather than RCC

29. Angiomyolipoma, Renal
• Most common benign renal solid mass
• 95% have identifiable fat on CT or MR
– Use NECT or MR to identify small foci of fat
– AML without fat is difficult or impossible to distinguish
from RCC by imaging (often hyperdense to kidney on
NECT)
– Highly echogenic at ultrasound, though imaging overlap
with small echogenic RCC
• Features favoring RCC: Halo, cystic components
• Multiple and bilateral in tuberous sclerosis
• May result in spontaneous bleeding

31. Renal Oncocytoma
• Benign epithelial tumor
• Often has central stellate scar (30-50%), though not
specific finding
• Segmental inversion pattern suggested, though
specificity also disputed
– Hypervascular component on corticomedullary phase
deenhances on nephrographic phase
– Hypovascular component on corticomedullary phase
retains contrast on nephrographic phase

33. Metastases and Lymphoma, Renal
• Often multiple, in patient with known primary
tumor
• Usually less vascular and less exophytic than RCC
• Multiple renal lymphoma patterns: Multifocal or
infiltrating tumor, diffuse bilateral enlargement
• Consider lymphoma if large tumor and
retroperitoneal adenopathy without renal vein
invasion

36. Urothelial Cell Carcinoma
• More infiltrative, less expansile than RCC
• May be part of multifocal tumor
– Bladder > kidney > ureter
• Most low-grade, superficial papillary masses
• 15% aggressive: Invade renal sinus and
parenchyma

38. Renal Trauma
• Renal hematoma may be indistinguishable
from tumor
– History (including possible invasive procedure like
biopsy) is key
• Traumatic injury will evolve quickly

41. Aneurysms and Arteriovenous
Malformations (Mimic)
• Vascular lesions can mimic tumor
• Key is multiphasic CT or MR during rapid bolus
of contrast medium or color Doppler

43. Rare but Important
• Renal Medullary Carcinoma
• Renal Tumors, Atypical and Rare
– Mesenchymal Tumor, Renal
– Juxtaglomerular Tumor
– Plasmocytoma, Renal
– Small Cell Carcinoma, Renal

44. Helpful Clues for Rare Diagnoses

45. Renal Medullary Carcinoma
• Rare, highly aggressive tumor
• Usually affects men with sickle cell trait

46. Renal Tumors, Atypical and Rare
• May arise from any mesenchymal component
of renal capsule, cortex, or medulla
• Generally cannot be diagnosed by imaging

48. Alternative Differential
Approaches
• Lesions that may be hyperdense on NECT:
Hyperdense cyst, RCC, oncocytoma, nonfat-
containing AML, transitional cell carcinoma

49. THANK YOU