S1-Guideline: Microscopically controlled surgery

Microscopically controlled surgery (MCS) comprises various methods allowing histologically proven complete resection of malignant tumors while at the same time sparing the tumor-free tissue in the immediate vicinity as much as possible. All procedures subsumed under MCS have in common the marking of the excised tissue for topographical orientation, which provides an assignment of remaining tumor remnants. Indications for MCS are malignant skin tumors in problem localizations as well as aggressive subtypes of skin tumors. Established indications for MCS include basal cell carcinoma, cutaneous squamous cell carcinoma, Bowen's disease as well as Bowen's carcinoma, dermatofibrosarcoma protuberans, melanoma in chronically light-damaged skin as well as acral lentiginous melanoma and Merkel cell carcinoma. For other tumors such as extramammary Paget's disease and various cutaneous sarcomas, evidence exists that MCS has demonstrated benefits, such as local recurrence rates. In addition, MCS is indicated when it is foreseeable that a complex closure technique is required and complete resection of the tumor must be assured. Various methods of MCS have been described, including 3D histology, horizontal method and Mohs surgery. A close cooperation of qualified surgeons and (dermato)pathologists as well as laboratory staff is essential for the successful application of MCS.