Mohs micrographic surgery (MMS) is a unique dermatologic surgery technique that allows the dermatologist to fill the concomitant roles of surgeon and pathologist. It is utilized for the extirpation of skin malignancy, with an emphasis on tissue preservation and immediate surgical margin evaluation. In MMS, the Mohs surgeon acts as the surgeon for physical removal of the lesion and the pathologist during evaluation of frozen section margins.1
Primary care providers (PCPs) are on the frontlines of management of cutaneous malignancy. Whether referring to Dermatology for biopsy or performing a biopsy themselves, PCPs can assure optimal treatment outcomes by guiding patients to evidence-based treatments, while still respecting the patient’s wishes. In this evidence-based review of the advantages, improved outcomes, and safety of Mohs surgery for the treatment of common and rare skin neoplasms, we provide our primary care colleagues with information on the indications, process (the order in which steps of the procedure are performed), and techniques used for treating cutaneous malignancies with Mohs surgery.
When is Mohs surgery appropriate?
MMS has typically been reserved for treatment of cutaneous malignancy in cosmetically sensitive areas where tissue preservation is key. In 2012, Connolly et al released appropriate use criteria (AUC) for MMS.2 (See “An app that helps clinicians apply the criteria for Mohs surgery.”) Within the AUC, there are 4 major qualitative and quantitative categories when considering referral for MMS:
- area of the body in which the lesion manifests
- the patient’s medical characteristics
- tumor characteristics
- the size of the lesion to be treated.2
Areas of the body are divided into 3 categories by the AUC according to how challenging tumor extirpation is expected to be and how critical tissue preservation is. Areas termed “H” receive the highest score for appropriate Mohs usage, followed by areas “M” and “L.”
SIDEBAR
An app that helps clinicians apply the criteria for Mohs surgery
“Mohs Surgery Appropriate Use Criteria” is a free and easy-to-use smartphone application to help determine whether Mohs micrographic surgery (MMS) is appropriate for a particular patient. Clinicians can enter the details of a recent skin cancer biopsy along with patient information into the app and it will calculate a score automatically categorized into 1 of 3 categories: “appropriate,” “uncertain,” and “not appropriate” for MMS. The clinician can then talk to the patient about a possible referral to a Mohs surgeon, depending on the appropriateness of the procedure for the patient and their tumor.
Patient medical characteristics that should be taken into account when referring for Mohs surgery are the patient’s immune status, genetic syndromes that may predispose the patient to cutaneous malignancies (eg, xeroderma pigmentosa), history of radiation to the area of involvement, and the patient’s history of aggressive cutaneous malignancies.
Tumor characteristics. The most common malignancies treated with MMS include basal cell carcinoma (BCC) and squamous cell carcinoma (SCC). These malignancies are further delineated through histologic evaluation by a pathologist or dermatopathologist. Aggressive features of a BCC on any area of the body that warrant referral to a Mohs surgeon include morpheaform/fibrosing/sclerosing histologic findings, as well as micronodular architecture and perineural invasion. Concerning histologic SCC findings that warrant Mohs surgery through the AUC include sclerosing, basosquamous, and small cell histology, as well as poorly differentiated and/or undifferentiated SCC.
Melanoma in situ and lentigo maligna, which are variants of melanoma limited to the epidermis without invasion into the underlying dermis, are included within the AUC for MMS. For invasive melanoma (melanoma that has invaded into the dermis or subcutaneous tissue), MMS has been shown to have marginal benefit but currently is not included within the AUC.3
Continue to: Due to excellent margin control...