Dermatologic Surgery, Lasers and Procedural Dermatology
Domain 8 tests procedural decision-making: margin, technique, device selection and safety.
Excision and biopsy
- Fusiform ellipse with a 3:1 length-to-width ratio, incision oriented along relaxed skin tension lines, undermining for closure.
- Punch biopsy for deep dermal or inflammatory lesions, shave for superficial lesions, excisional for suspected melanoma, incisional for large tumours.
- Mohs micrographic surgery for recurrent, morpheaform, large or cosmetically sensitive basal and squamous cell carcinomas and selected melanoma in situ.
Lasers and energy devices
- Selective photothermolysis: match wavelength to chromophore (haemoglobin 532/595 nm, melanin 694/755/1064 nm, water 2940/10600 nm) and pulse duration to thermal relaxation time.
- Pulsed dye laser for port-wine stains and telangiectasia; Q-switched lasers for pigment; fractional CO2 or erbium:YAG for resurfacing; excimer laser for vitiligo.
- Complications include pigmentary change, scarring and burns. Eye protection and smoke evacuation are mandatory.
Injectables and adjuncts
Botulinum toxin for dynamic lines and hyperhidrosis; hyaluronic acid fillers with vascular occlusion as an emergency; chemical peels and cryotherapy chosen by depth.
Worked example
A 0.8 cm recurrent morpheaform basal cell carcinoma on the nasal ala. Best option is Mohs micrographic surgery. Reasoning: subclinical extension, recurrence and a cosmetically sensitive site; frozen-section margin control preserves tissue.
Traps
Do not use shave biopsy for suspected melanoma. Do not apply a 2 cm margin to a 0.6 mm melanoma. Do not perform laser on recently tanned skin without discussing pigment risk.