What is the best imaging approach for a patient presenting with a lump in the scalp?

Imaging Approach for Scalp Lumps

For a scalp lump, the initial imaging modality of choice is MRI with intravenous contrast, as it provides superior soft tissue characterization and helps distinguish benign from malignant lesions. 1, 2

Risk Stratification First

Before ordering imaging, assess whether the patient is at increased risk for malignancy based on these specific criteria:

• Duration: Mass present ≥2 weeks without significant fluctuation, or uncertain duration 3
• Physical characteristics: Fixation to adjacent tissues, firm consistency, size >1.5 cm, or ulceration of overlying skin 3
• Patient history: Lack of infectious etiology, prior malignancy history, smoking history 3, 4
• Associated symptoms: Neurological deficits, cranial nerve abnormalities, or systemic symptoms 5

Imaging Selection Algorithm

For Patients at Increased Risk for Malignancy:

Order MRI with IV contrast as the primary imaging modality 1, 2

• MRI provides superior soft tissue contrast and anatomic detail compared to CT 3, 2
• Contrast enhancement is critical for characterizing the mass, delineating borders, and identifying potential intracranial extension 1
• Post-contrast T1-weighted sequences in multiple planes (axial, sagittal, coronal) should be specifically requested 1

Alternative: CT with contrast if MRI is contraindicated 3, 1

• Use CT when patient has claustrophobia, pacemaker, or other MRI contraindications 3
• CT is faster (3-5 minutes vs 45-60 minutes for MRI) and better tolerated by anxious patients 3
• CT provides excellent bone detail for evaluating skull involvement 2, 4

For Patients NOT at Increased Risk:

• Clinical follow-up may be appropriate initially 3
• Document a clear plan for reassessment and criteria that would trigger imaging 3
• If imaging becomes necessary, follow the same algorithm as above 1

Critical Ordering Details

When ordering imaging, include these specific elements:

• Anatomical location: "Scalp mass" with precise location (frontal, parietal, occipital, temporal) 1
• Clinical indication: Duration, size, consistency, associated symptoms 1
• Contrast specification: "With IV contrast" unless contraindicated by severe renal insufficiency or contrast allergy 1
• Risk factors: Prior malignancy, smoking history, concerning physical exam features 1, 4

Common Pitfalls to Avoid

Do not order CT without and with contrast - this doubles radiation exposure (equivalent to 300 chest X-rays) with minimal diagnostic benefit 3, 1

Do not omit contrast unless specifically contraindicated - non-contrast studies provide significantly less diagnostic information for characterizing masses 1

Do not assume benign etiology based on painless presentation - metastatic lesions to the scalp are often painless and can be the first presentation of occult malignancy 4, 6, 5

Do not delay imaging with empiric antibiotics unless there are clear signs of bacterial infection (warmth, erythema, fever, tenderness) 3

Special Considerations

• The scalp is a common site for metastatic disease due to rich vascularity 7
• Malignant scalp lesions can erode through skull and extend intracranially 4, 5
• Over 50% of scalp lesions are benign cysts, but imaging is essential to exclude malignancy in high-risk patients 2
• If imaging reveals osteolytic skull lesions, consider metastatic workup including chest CT, as lung and thyroid carcinomas commonly metastasize to skull 4, 6