History of Mohs Surgery
Development of the Mohs Technique
The Mohs technique was developed in the 1930’s by Dr. Frederic Mohs, a general surgeon at the University of Wisconsin. This important development occurred while he was studying various injectable irritants to evaluate the live inflammatory response in transplantable rat cancers and normal tissue. Dr. Mohs noted that injected 20% zinc chloride solution inadvertently caused tissue necrosis in tumor and normal tissue. Further, he found that microscopic examination of this necrotic tissue showed well-preserved tumor and cell histology, the same as if the tissue had been excised and immersed in a fixative solution. This discovery was the basis for a method in which cancers could be excised under complete microscopic control. This fixed tissue technique was utilized for over a decade, with Dr. Mohs its pioneer developer, greatest advocate, and lone practitioner.
Long-term follow-up of Dr. Mohs’ patients was carefully documented and gave further testimony to the effectiveness of this treatment. In 1953 a revolutionary breakthrough occurred while filming the removal of an eyelid carcinoma for educational purposes. An involved margin in the first level caused a delay in filming, a development which necessitated the utilization of horizontal frozen sections for the second and third levels. This fresh tissue technique worked so well that Dr. Mohs continued to use it for most eyelid cancers. He also found the technique useful for small- and medium-sized cancers at other sites, and subsequently used the fresh tissue technique in the treatment of many other skin cancers. In 1969 Dr. Mohs reported the use of the fresh tissue technique for sixty-six basal cell carcinomas and for squamous cell carcinomas of the eyelid, with five-year cure rates of 100%. A corroborating series of data was instrumental in convincing the medical community of the validity of the fresh tissue technique, which had not yet largely replaced the fixed tissue technique. It is now well-established that the five-year cure rates using fresh tissue technique are equivalent to that of the fixed tissue technique. The fixed tissue technique is still recommended by some Mohs surgeons, however, for selected tumors.
Dermatologists’ Adoption of Mohs Surgery
Because of its tremendous value in treating skin cancer, dermatologists enthusiastically adopted the Mohs technique and now are its primary practitioners. From the 1950s to the 1970s, Mohs surgical training was conducted on a largely informal basis. Training sessions lasted from several days to several months and took place both in Dr. Mohs’ Chemosurgery Clinic and in the offices of “second generation” physicians who had learned the technique directly from Dr. Mohs. In 1967 the American College of Chemosurgery was established and consisted primarily of dermatologists. By the 1970s, some dermatology Residency programs had begun offering Mohs surgical training. In the 1980s the American College of Chemosurgery began sponsoring post-residency fellowship training in Mohs surgery, and in 1986 its name was changed to the American College of Mohs Micrographic Surgery and Cutaneous Oncology, reflecting the predominance of the fresh tissue technique. This organization is now known as the American College of Mohs Surgery (ACMS).
Today all U.S. dermatology Residency training programs are required to provide exposure to the Mohs technique, and in many cases second- and third-year Residents receive extensive hands-on experience in the procedure. As the incidence of skin cancer increases, it is imperative that all dermatologists receive quality training in this important procedure, both in Residency and once in practice. In addition to strongly advocating extensive Mohs surgical training in Residency, the ASMS has developed two separate medical education courses to teach and reinforce surgical skills and related medical and procedural modalities.