Imaging and Diagnosis of Heterogeneous Masses

Introduction to Heterogeneous Masses

• Heterogeneous masses can be found in various parts of the body, including the kidneys, soft tissues, and breast, and require comprehensive evaluation to determine their nature and appropriate management, as recommended by the American College of Radiology and the American Urological Association 1, 2

Renal Masses

• Ultrasound can help determine if a renal mass is solid or cystic and assess for internal vascularity, which is more common in malignant lesions, according to the American College of Radiology 1
• Renal masses are a biologically heterogeneous group ranging from benign to aggressive malignancies, as stated by the American Urological Association 2
• Heterogeneous enhancement, irregular borders, and invasion of surrounding structures suggest renal cell carcinoma, according to the American Urological Association 2
• For renal masses, biopsy should be considered for indeterminate lesions prior to definitive treatment, as recommended by the American Urological Association 2
• A multiphase CT protocol including unenhanced, corticomedullary/arterial, and nephrographic phases with thin-slice acquisition (≤5mm) is recommended for evaluating a renal mass, as per the American College of Radiology 3, 4
• The Bosniak classification system requires assessment of enhancing nodules, walls, or septa within cystic masses, necessitating both unenhanced and contrast-enhanced phases for accurate classification, as recommended by the American College of Radiology 3
• MRI with gadolinium has similar diagnostic performance to CT when CT with contrast is contraindicated, and contrast-enhanced ultrasound (CEUS) is useful for differentiating cystic from solid lesions and characterizing complex renal masses, as supported by the American College of Radiology 3
• Tc-99m sestamibi SPECT/CT is helpful when oncocytoma is suspected, as recommended by the American College of Radiology 3
• Small renal calculi (4-5mm) are typically monitored rather than requiring immediate intervention, have a reasonable chance of spontaneous passage, and should be followed with appropriate imaging, with active surveillance appropriate for asymptomatic small renal calculi (4-5mm) and follow-up imaging recommended to monitor for growth or obstruction 5
• If stones become symptomatic or show growth, consider intervention based on stone size, location, and symptoms, with options including shock wave lithotripsy (SWL) or ureteroscopy (URS) 5

Soft Tissue Masses

• Heterogeneous signal on MRI with areas of necrosis or hemorrhage is concerning for soft tissue sarcoma, according to the American College of Radiology 1

Breast Masses

• Heterogeneous breast masses require comprehensive evaluation with mammography and ultrasound, as recommended by the American College of Radiology 6
• Ultrasound should be geographically correlated with palpable masses to determine their nature, according to the National Comprehensive Cancer Network 7
• Complex cystic masses with solid components in the breast warrant biopsy due to increased risk of malignancy, as recommended by the National Comprehensive Cancer Network 7

Biopsy Considerations

• Ensure adequate sampling of different areas within heterogeneous masses to avoid sampling error, as stated by the European Society for Medical Oncology 8
• Image-guided core needle biopsy is preferred for most heterogeneous masses, with adequate sampling of different areas within the mass, as recommended by the European Society for Medical Oncology 8

Imaging Protocols and Follow-up

• Non-contrast MRI still provides valuable information through morphologic assessment and diffusion-weighted imaging if contrast is contraindicated 9
• Dual-energy CT can help overcome pseudoenhancement issues and differentiate solid tumors from hyperdense cysts, according to the American College of Radiology 3
• After MRI characterization, routine follow-up imaging is recommended for Bosniak I or II lesions, while Bosniak IIF lesions require follow-up imaging at 6, 12, and 24 months, and Bosniak III or IV lesions require consideration of surgical consultation 3
• Follow-up imaging in 6-12 months is recommended to assess for stone growth, development of hydronephrosis, and new stone formation 5
• For patients with confirmed nephrocalcinosis, laboratory tests such as serum calcium, phosphorus, and parathyroid hormone levels, and urine calcium, phosphorus, and citrate levels should be considered to identify underlying causes, as per the American College of Radiology 10
• The American College of Radiology recommends monitoring renal function with serum creatinine measurements and considering nephrology referral if significant nephrocalcinosis is identified 11

Coding and Documentation

• The American College of Radiology recommends using specific ICD-10 codes for initial evaluation of indeterminate renal masses, including:

  ICD-10 Code	Description
  D41.0	Neoplasm of uncertain behavior of kidney
  R93.4	Abnormal findings on diagnostic imaging of urinary organs
  N28.89	Other specified disorders of kidney and ureter

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• For patients with contraindications to CT contrast, the American College of Radiology suggests considering MRI with the appropriate ICD-10 code D41.0, and documenting the contrast contraindication in the order, with the ACR Appropriateness Criteria stating that CT abdomen without and with IV contrast is usually appropriate for the initial imaging of an indeterminate renal mass in patients without contraindications to iodinated contrast 3