Cryoablation

Principle

Cryoablation (cryotherapy) uses liquid nitrogen (or another cryogen) to freeze and destroy targeted skin lesions - a simple, widely used office-based technique for a range of benign and pre-malignant lesions
One of the most common dermatological office procedures given its simplicity, low cost, and short procedure time
Rapid freezing causes intracellular ice crystal formation, disrupting cell membranes and causing cell death, followed by an inflammatory response and tissue sloughing over subsequent days - the freeze-thaw cycle (often repeated) is what produces effective tissue destruction

Appropriate for: actinic keratoses, viral warts, seborrhoeic keratoses, and some superficial basal cell carcinomas in selected circumstances - lesions where histological margin assessment is not essential (i.e. where the clinical diagnosis is confident and malignancy risk/behaviour is well understood)
Not appropriate when tissue diagnosis is needed (e.g. a lesion where melanoma is a differential, or where histological margin clearance matters) - cryotherapy destroys tissue without providing a specimen for histology

Treatment typically causes local blistering/crusting over 1-2 weeks as the destroyed tissue sloughs; multiple treatment sessions are sometimes needed for complete clearance of thicker lesions
Post-treatment hypopigmentation is a recognised, sometimes permanent cosmetic side effect, particularly relevant in darker skin types where this should be specifically discussed before treatment

Actinic keratosis, viral warts, seborrhoeic keratosis, superficial basal cell carcinoma (in appropriate circumstances)

Cryotherapy should only be used when the clinician is confident of the clinical diagnosis without needing histological confirmation - using it on a lesion where malignancy (particularly melanoma) has not been adequately excluded risks destroying diagnostic tissue and delaying appropriate treatment

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