Frederic E. Mohs, MD, and the history of zinc chloride

The history of zinc chloride therapy before and including Frederic E. Mohs' (1910-2002) early contributions to dermatologic oncology is presented. In 1932, Mohs devised a method of cutaneous surgery that employed zinc-chloride paste to devitalize basal or squamous cell carcinoma. Because zinc chloride coagulates malignant tissue without destroying cellular architecture, he described the surgery and its preservative effect as the fixed-tissue method. This method involved the serial removal of devitalized malignant tissue and the freezing and histologic examination of each layer; the process was continued until a cancer-free plane was reached. In 1953, a modified version of the micrographic system, the fresh-tissue method, was introduced. For improved efficiency, Mohs retained the systematic mapping of a neoplasm but eliminated the chemical escharotic. Although the fresh-tissue method has become the preferred treatment mode, zinc-chloride paste therapy remains in use today. Although the history of Mohs micrographic surgery is well documented, its background has not received sufficient attention. This paper surveys the chemical synthesis of zinc chloride, the formulation of zinc-chloride paste as a cutaneous escharotic, and the extent to which Mohs' method compares with those of 19th and early 20th century predecessors.