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TREATMENT PLANNING TARGET VOLUME DEFINITION

➢ BASAL CELL CANCER : 5mm margin for well defined lesions, 7–10mm margin for poorly defined, large, infiltrative, morphoeic and/or sclerotic types of BCC.

➢ SQUAMOUS CELL CANCER : at least 10mm margin, if the lesion is <20mm it is necessary to add a margin of 10–15mm, for lesions >20mm the margin of 15– 20mm is usually required. ➢ MERKEL CELL CARCINOMA : at least 20–30mm peripheral margin, deep margin at least 5–10mm below visible extension (by imaging). Post-operative cases: whole surgical site to be included. Peripheral and deep margins as per histopathology report from surgery.

➢ An extra margin is needed (PTV) to account for any misalignment for radionuclide and electronic based shielded applicators and for flaps.