What is the best approach to analyze lesions on the head?

Analyzing Head Lesions: Diagnostic Approach

For suspicious lesions on the head, dermoscopy combined with visual inspection is the most effective initial diagnostic approach, improving melanoma detection sensitivity by 16% over visual inspection alone when performed in-person, and should be followed by complete surgical excision with histopathological examination for any lesion concerning for malignancy. 1, 2

Initial Clinical Assessment

Key Features to Document

• Lesion characteristics: Size (measure in millimeters), shape (round, ovoid, irregular), color (pigmented vs. non-pigmented, uniform vs. variegated), and presence of a stalk or pedunculated appearance 3, 2
• Distribution pattern: Solitary versus multiple lesions, symmetric versus asymmetric presentation 3
• Changes over time: New onset, increasing size, color change, bleeding, or ulceration 3, 2
• Patient demographics: Age (risk increases >65 years), skin type (Fitzpatrick I-II at higher risk), and history of sun exposure 4

Dermoscopic Examination

When to Use Dermoscopy

Dermoscopy should be performed on all suspicious head lesions including large pigmented lesions, small hypo/depigmented lesions, and any lesion that has changed in shape or color. 5

Diagnostic Accuracy

• In-person dermoscopy plus visual inspection achieves 92% sensitivity at 80% specificity, compared to 76% sensitivity for visual inspection alone 1
• For a population with 12% melanoma prevalence (typical for referred lesions), dermoscopy reduces missed melanomas by 19 per 1000 lesions examined 1
• Dermoscopy is particularly valuable for detecting melanoma on the scalp, which behaves more aggressively than melanomas at other sites 2

Key Dermoscopic Features to Assess

1. Vascular patterns: Morphology and arrangement of blood vessels 6
2. Pigmentation patterns: Presence of "comma-shaped" hairs (ectothrix infection in tinea capitis), black dots, or irregular pigment networks 3, 7
3. Colors: Number and distribution of colors present 6
4. Follicular abnormalities: Hair shaft changes or follicular plugging 6

Critical Pitfall

Dermoscopy findings must always be interpreted within the clinical context—never rely on dermoscopy alone without considering patient history and macroscopic examination. 6

Imaging for Specific Clinical Scenarios

For Suspected Infectious/Inflammatory Lesions (e.g., Tinea Capitis)

• Wood's lamp examination: Identifies M. canis-affected hairs by fluorescence 3
• Dermoscopy: Visualizes black dot hair stubs, comma-shaped hairs (white children with ectothrix), or corkscrew hairs (Afro-Caribbean children) more clearly 3

For Suspected Neoplastic Lesions

MRI is the preferred imaging modality when evaluating head lesions with concern for deep tissue involvement, skull base extension, or intracranial spread. 3

• MRI orbits, face, and neck with and without contrast: Optimal for characterizing soft tissue masses, assessing depth of invasion, and evaluating relationship to adjacent structures 3
• CT with contrast: Complementary to MRI for detecting calcification, assessing bone involvement (erosion, sclerosis, periosteal reaction), and evaluating foreign bodies 3
• Thin-cut high-resolution sequences: Essential for detailed assessment of small lesions and their relationship to critical structures 3

Tissue Sampling Strategy

When Complete Excision is Indicated

Complete surgical excision with histopathological examination is the standard of care for any head lesion suspected to be neoplastic, as partial sampling risks misdiagnosis and inadequate assessment. 2

Excision Technique

• Use elliptical excision with 2-3mm margins of normal skin for initial diagnostic excision if the lesion appears clinically benign 2
• Use scalpel rather than laser or electrocautery to preserve tissue architecture for accurate histopathological diagnosis 2
• Orient the incision to allow wider re-excision if malignancy is diagnosed, minimizing need for complex reconstruction 2
• Document excision margins in the operative note 2

Special Considerations for Scalp Lesions

Scalp melanomas require subperiosteal resection rather than subgaleal resection to reduce locoregional recurrence, given their more aggressive behavior. 2

Alternative Sampling for Tinea Capitis

• Pluck affected hairs (especially those fluorescent under Wood's lamp for M. canis) 3
• Blunt scalpel scraping to remove hair and scalp scale 3
• Cytobrush sampling: Improves sensitivity and time to positive culture, though prevents microscopic examination 3
• Multiple sampling methods (e.g., scalp scraping plus brush) increase yield of dermatophyte fungus 3

Laboratory Processing

For Suspected Fungal Infections

• Microscopy: Mount specimens in 10-30% potassium hydroxide with or without calcofluor; examine for hyphae and arthroconidia 3
• Culture: Use Sabouraud agar with cycloheximide; incubate for at least 2 weeks (3 weeks if T. verrucosum suspected) 3
• Susceptibility testing is not indicated as resistance development is rare 3

For Suspected Neoplasms

The pathology specimen must include patient age, sex, anatomic site, complete excision assessment with margin measurement, and specific parameters based on lesion type. 2

For Melanoma

• Breslow thickness (most powerful prognostic factor) 3
• Clark level (for thin melanomas <1mm) 3
• Presence of ulceration, regression, mitotic rate, vascular invasion, and neurotropism 3, 2

For Sarcomas

• Depth of invasion, necrosis, lymphovascular invasion, and perineural invasion 2

Critical Pitfalls to Avoid

1. Never perform incisional or shave biopsy of pigmented lesions, as this compromises depth assessment and may lead to misdiagnosis 2
2. Do not use tissue-destructive techniques (laser, electrocautery) that prevent accurate histopathological assessment 2
3. Avoid empirical antibiotic treatment unless clear signs of bacterial infection are present, as this delays diagnosis of malignancy 2
4. Do not rely on radiography for head lesion evaluation—it is insufficient to detect relevant pathology 3
5. Never skip dermoscopy training—accuracy improves significantly with experience and formal training, particularly for less expert observers 1