Indications and limitations of Mohs micrographic surgery.

Mohs micrographic surgery is most suitable for cutaneous and mucosal neoplasms that exhibit a contiguous growth pattern and have minimal potential for metastases. Thus, a higher failure rate will be observed for tumors that exhibit multicentricity, disconnected foci, or give rise to metastases or satellite lesions. Because of its superior microscopic control, MMS offers the maximum chance for cure and preservation of normal tissue in properly selected tumors. Consequently, MMS is the treatment of choice for tumors located in cosmetically and functionally important areas of the head and neck (such as the periocular and perinasal areas), not only because of its tissue-sparing properties but also because tumors in some of these same anatomic areas also exhibit a high recurrence rate when managed by routine modalities. Variables to consider when selecting MMS to manage a neoplasm include, in addition to its anatomic location, its histology, its size, its tendency for recurrence, and whether or not it has been inadequately or previously treated. Field-fire BCC and ill-defined tumors are also best managed by MMS. When the management of a tumor exceeds the capabilities of the Mohs surgeon, an interdisciplinary approach utilizing other oncologic specialists is required (for example, reconstructive surgery, preservation of vital anatomic structures, deeply penetrating and extensive tumors, or the presence of or high risk for metastases). Because MMS is usually performed with local anesthesia on an outpatient basis, it is cost effective, safe, and extends operability to patients who are poor candidates for general anesthesia. However, when a multidisciplinary approach is employed, general anesthesia is often required. If the neoplasm is extensive, several operative sessions may be required to complete the extirpation of the tumor and the reconstruction of the defect. Although offering the greatest chance of cure for many difficult cutaneous neoplasms, MMS may at times become tedious and prolonged. Frozen sections are adequate in tracing out the microscopic extensions of most neoplasms; however, permanent sections may at times be required to provide the best microscopic control of margins, and this, too, may prolong the procedure. Histologic preparations must be of superior quality to ensure maximum microscopic control, and the surgical specimens removed must be properly oriented. On microscopic examination, benign, reactive changes and normal anatomic structures must be distinguished from tumor to avoid the unnecessary sacrifice of normal tissue, and inflammation, which may obscure tumor, must be carefully scrutinized.(ABSTRACT TRUNCATED AT 400 WORDS)