USG Features of Testicular Malignancy

General Principles

Key USG Features

1. Intratesticular Location

• The single most important distinguishing feature. Virtually all testicular malignancies are intratesticular.
• Extratesticular masses are almost always benign (epididymal cysts, lipomas, etc.).

2. Echogenicity - Hypoechoic Mass

• The classic appearance of a germ cell tumor (GCT) is a hypoechoic mass relative to normal surrounding testicular parenchyma.
• This is the hallmark finding in the majority of tumors.

3. Echogenicity Differences by Histology

• Seminoma typically presents as a homogeneous, hypoechoic mass.
• NSGCT is more likely to be heterogeneous with calcification and/or cystic components (occurring in up to 40% of NSGCTs).
• Cystic spaces and calcifications are uncommon in seminoma (only 10-30%), but common in NSGCT/teratoma.

4. Increased Vascularity on Color Doppler

• Increased blood flow within the lesion on color Doppler sonography is suggestive of malignancy.
• However, absence of increased flow does not exclude GCT - small or burned-out tumors may show no increased vascularity.

5. Multiple Lesions

• Two or more discrete intratesticular lesions may be identified.
• Given the 2% incidence of bilateral GCT, both testes must always be evaluated sonographically.

6. Testicular Microlithiasis

• Defined as ≥5 punctate, non-shadowing echogenic foci per image within the testicular parenchyma.
• Represents calcifications within seminiferous tubules.
• Commonly seen in association with testicular malignancy, but its independent role as a risk predictor is controversial - microlithiasis alone should not prompt further evaluation in an otherwise normal testis.

7. Burned-Out Primary Tumor

• In men with advanced/metastatic GCT and a normal testicular examination, USG may show a small scar, stellate calcification, or coarse calcification - indicating a "burned-out" primary.
• GCTs are among the most common neoplasms to undergo spontaneous regression (seminoma being the most frequent subtype).
• Even these patients should undergo radical orchiectomy if intratesticular lesions are found sonographically.

8. Small Impalpable Lesions

• Lesions <10 mm that are impalpable represent a diagnostic dilemma - up to 20-50% may represent small GCT (usually seminoma).
• Risk of malignancy increases with lesion size:
  • <1 cm: ~50% malignant
  • 1-2 cm: ≥80% malignant

9. Associated Findings

• Hydrocele: Present in ~10% of testicular tumors; does not exclude malignancy
• Testicular enlargement: Diffuse or focal
• Loss of normal testicular architecture

Summary Table

Role of MRI