LAUSR

Adjuvant radiation is used after surgical treatment of squamous cell carcinomas (SCCs) and other aggressive tumors to prevent recurrence. Irradiation protocols depend on type, location, extent of tumor, patient age, and comorbidites. Postradiation changes to the treated skin and underlying tissue have beenwell described and are divided into early and chronic stages, the latter of which can occur months or years after exposure. Clinical findings and sequelae of previous radiation therapy are well known to dermatologists, and can consist of scar, skin atrophy, telangiectasias, ulceration, and pigmentation changes. Irradiated skin has a higher risk of developing new or recurrent keratinocyte carcinomas. Subcutaneous tissue and skeletalmuscle is often present in Mohs histology sections. The surgeon needs to be aware of the histologic features of irradiated skin to correctly identify and differentiate tumor from confounding radiation-related background changes in the subcutis and muscle below.