What is the appropriate management for scalp skin lesions?

Management of Scalp Skin Lesions

For suspicious scalp lesions, perform complete excisional biopsy with a 2 mm margin of normal skin using a scalpel under local anesthesia, rather than partial biopsy or tissue-destructive methods, to enable accurate histopathological diagnosis and assessment of prognostic factors. 1

Initial Clinical Assessment

Examination Technique

• Examine the entire scalp systematically, as scalp lesions are frequently missed during routine dermatological consultations due to hair coverage 1, 2
• The scalp requires careful inspection as it harbors approximately 2% of all cutaneous neoplasms, with worse prognosis compared to other anatomical sites 2

Clinical Criteria for Malignancy Suspicion

Evaluate pigmented lesions using the ABCDE criteria 1:

• A: Asymmetry
• B: Irregular borders
• C: Heterogeneous color
• D: Large diameter (>7 mm)
• E: Evolution (recent change in size, color, or shape)

Additional concerning features include hypersensitivity, bleeding, and inflammation 1

Dermoscopy Considerations

• Dermoscopy can improve diagnostic accuracy for pigmented lesions and differentiate melanocytic from non-melanocytic lesions (seborrheic keratosis, pigmented basal cell carcinoma, hemangioma) 1
• Should only be used by experienced practitioners and is not recommended as routine practice 1
• For tinea capitis, dermoscopy can visualize black dot hair stubs and comma-shaped hairs more clearly 1

Diagnostic Sampling Strategy

For Suspected Malignant Lesions

Complete excisional biopsy is mandatory rather than partial biopsy for the following critical reasons 1:

• Eliminates need for further treatment if benign
• Prevents misdiagnosis from partial examination
• Allows assessment of all histological parameters, particularly maximum Breslow thickness
• Enables accurate margin clearance determination

Excision Technique

• Use a scalpel with 2 mm margin of normal skin under local anesthesia 1
• Create elliptical incision with long axis parallel to skin lines to facilitate potential re-excision with minimal skin loss 1
• Never use laser or electro-coagulation, as tissue destruction compromises diagnosis and prognostic assessment 1
• Document excision margins in the operation note 1
• Avoid frozen sections 1

For Suspected Fungal Infections (Tinea Capitis)

Multiple sampling methods increase diagnostic yield 1:

• Pluck affected hairs (especially those fluorescing under Wood's lamp for Microsporum canis) 1
• Blunt scalpel scraping to remove hair and scalp scale 1, 3
• Cytobrush sampling improves sensitivity and time to positive culture, though prevents microscopic examination 1
• Gauze swabs provide equally effective and convenient alternative 1
• Store specimens in paper or card packs 1

Laboratory Processing

For Suspected Malignancy

Histopathological report must include 1:

• Diagnosis confirming melanocytic nature and malignancy
• Maximum tumor thickness in millimeters (Breslow method)
• Assessment of complete excision of invasive and in situ components
• Microscopic measurement of shortest clearance extent
• Clark level of invasion
• Presence and extent of regression
• Presence and extent of ulceration

For Suspected Fungal Infection

• Mount specimens in 10-30% potassium hydroxide with or without calcofluor for microscopy 1, 3
• Culture on Sabouraud agar with cycloheximide, incubated for at least 2 weeks 1, 3
• For suspected Trichophyton verrucosum (cattle exposure), incubate up to 3 weeks 1
• Antifungal susceptibility testing is not routinely indicated 1

Treatment by Lesion Type

Actinic Keratosis on Scalp

Imiquimod 5% cream is first-line topical therapy for clinically typical, non-hyperkeratotic, non-hypertrophic actinic keratoses in immunocompetent adults 1, 4:

• Apply 2 times per week for 16 weeks to defined 25 cm² treatment area 4
• Apply before sleep, leave for 8 hours, then wash with mild soap and water 4
• Achieves 50% complete clearance rate in randomized controlled trials 1
• 46% and 44% complete clearance in two large studies versus 3-4% with vehicle 4

Alternative options 1:

• 5-Fluorouracil 0.5% in 10% salicylic acid: 55.4% complete clearance versus 15.1% with vehicle
• Photodynamic therapy: 88-100% clearance at 3 months, with 68-89% remaining clear at 17-50 months 1
• Cryotherapy: Appropriate for individual lesions

Squamous Cell Carcinoma In Situ (Bowen's Disease)

• Photodynamic therapy with MAL: 88-100% clearance at 3 months 1
• Radiotherapy: Effective but avoid on lower legs due to poor healing; can be used on scalp 1
• CO₂ laser: Limited evidence, considered for challenging sites 1

Tinea Capitis

Oral antifungal therapy is required for eradication 1:

• Itraconazole 100 mg daily: 87% mycological cure rate (superior to griseofulvin's 57%) 3
• Terbinafine: Superior for Trichophyton tonsurans infections 3
• Treatment endpoint should be mycological cure, not just clinical response 3
• Continue until mycological clearance documented with repeat sampling 3

Prevention measures 3:

• Cover lesions to prevent spread
• Keep affected areas clean and dry
• Screen and treat family members for anthropophilic species

Common Pitfalls to Avoid

Diagnostic Errors

• Never perform partial biopsy of suspected melanocytic lesions—risk of misdiagnosis and inability to assess Breslow thickness 1
• Avoid tissue-destructive methods (laser, electrocautery) that compromise histological assessment 1
• Do not rely on clinical improvement alone for fungal infections—confirm mycological cure 3

Treatment Errors

• Do not stop antifungal treatment early based only on clinical improvement rather than mycological cure 3
• Do not extend imiquimod treatment beyond 16 weeks due to missed doses or rest periods 4
• Consider secondary bacterial infection in inflammatory cases 3
• Do not use radiotherapy on lower leg lesions due to poor healing (33% failure rate) 1

Follow-up Considerations

• Lesions not responding to standard treatment require re-evaluation and possible excision to rule out invasive squamous cell carcinoma 1
• For actinic keratosis, response cannot be adequately assessed until local skin reactions resolve 4
• Patients with ≥10 actinic keratoses have threefold higher risk of squamous cell carcinoma and warrant closer surveillance 1