Mohs micrographic surgery for the treatment of malignant melanoma

[Mohs micrographic surgery for skin cancers: A 10 year - single-center series of 548 patients treated by formalin-fixed tissue Mohs surgery assessing the impact of reduced margins]

AIM

Only few robust studies specify the indications of Mohs Surgery techniques in skin tumors. The aim of this work was to carry out a review of almost 10 years of experience, assessing the impact of reduced margins on reconstruction, and proposing a management algorithm in the light of the literature.

PATIENT AND METHODS

All the records of patients having benefited from a Mohs technique in our center were retrospectively compiled from January 2011 until January 2020. A formalin-fixed tissue Mohs surgery was used. An impact assessment of reduced margins was made both on the excisional surface but also on the improvement of the reconstruction.

RESULTS

548 patients were included. Complete tumour clearance was achieved with one surgical stage in 71% of cases. The excisional surface of tumours located in the periorbital and nasal areas was significantly more often reduced compared to other areas (P=0,020). The improvement of the reconstruction was deemed significant in the periorbital and nasal areas; as well as for tumours located on limbs and trunk linked with Dermatofibrosarcoma management.

CONCLUSION

This study underlines the interest of assessing the clinical relevance of reducing margins depending on the tumor location. Our single-center experience feedback on a large series allows to clarify Mohs technique indications by means of a literature review.

Current perspectives on Mohs micrographic surgery for melanoma

Mohs micrographic surgery (MMS), a specialized surgical excision technique used primarily in the treatment of skin cancers, is tissue sparing and provides optimal margin control through evaluation of 100% of both the peripheral and deep margin. The use of MMS for the treatment of malignant melanoma (MM) and melanoma in situ (MIS) has been slow in gaining the same widespread acceptance that it has for keratinocyte carcinomas despite its cost-effectiveness and the growing body of evidence demonstrating similar or improved cure rates to standard wide local excision. However, modern advances in immunohistochemical staining have continued to greatly enhance the ability of Mohs surgeons to interpret MMS frozen sections of melanoma specimens – the primary concern of most opponents of MMS for melanoma. These advances, coupled with an increased recognition by professional organizations of the utility of MMS in treating MM and MIS, have led to a rise in the use of MMS for melanoma in recent years. Given the expanding role of MMS in the treatment of cutaneous melanoma, this manuscript will describe how MMS is performed, discuss the rationale and current evidence regarding the use of MMS for MM and MIS, review the immunohistochemical stains currently available for use in MMS, and consider special situations and future directions in this area of growing interest.

Head and neck melanoma (excluding ocular melanoma): United Kingdom National Multidisciplinary Guidelines

This is the official guideline endorsed by the specialty associations involved in the care of head and neck cancer patients in the United Kingdom. This paper provides consensus recommendations on the management of melanomas arising in the skin and mucosa of the head and neck region on the basis of current evidence.

Update and Review on the Surgical Management of Primary Cutaneous Melanoma

The surgical management of malignant melanoma historically called for wide excision of skin and subcutaneous tissue for any given lesion, but has evolved to be rationally-based on pathological staging. Breslow and Clark independently described level and thickness as determinant in prognosis and margin of excision. The American Joint Committee of Cancer (AJCC) in 1988 combined features from each of these histologic classifications, generating a new system, which is continuously updated and improved. The National Comprehensive Cancer Network (NCCN) has also combined several large randomized prospective trials to generate current guidelines for melanoma excision as well. In this article, we reviewed: (1) Breslow and Clark classifications, AJCC and NCCN guidelines, the World Health Organization's 1988 study, and the Intergroup Melanoma Surgical Trial; (2) Experimental use of Mohs surgery for in situ melanoma; and (3) Surgical margins and utility and indications for sentinel lymph node biopsy (SLNB) and lymphadenectomy. Current guidelines for the surgical management of a primary melanoma of the skin is based on Breslow microstaging and call for cutaneous margins of resection of 0.5 cm for MIS, 1.0 cm for melanomas ≤1.0 mm thick, 1-2 cm for melanoma thickness of 1.01-2 mm, 2 cm margins for melanoma thickness of 2.01-4 mm, and 2 cm margins for melanomas >4 mm thick. Although the role of SLNB, CLND, and TLND continue to be studied, current recommendations include SLNB for Stage IB (includes T1b lesions ≤1.0 with the adverse features of ulceration or ≥1 mitoses/mm²) and Stage II melanomas. CLND is recommended when sentinel nodes contain metastatic deposits.

Histologic pitfalls in the Mohs technique

The success of the Mohs procedure depends on the reliability of each step in the technique. Pitfalls in histologic preparation of the tissue specimens may occur during debulking, excising, orienting, creating the map, sectioning, inking, tissue flattening and freezing, cutting, slide fixation, staining, and mapping the tumor. Challenges are also present in interpreting the slides. Diagnostic pitfalls include floaters, inflammatory conditions resembling tumor, and perineural invasion. The technique requires time, teaching, and a sufficient quantity of cases from which to learn, as well as attention to the pitfalls that occur while processing tissue specimens and interpreting and mapping the histology.

Surgery of primary melanomas

Surgery remains the mainstay of melanoma therapy, regardless of the tumor site. Only the early diagnosis combined with proper surgical therapy currently gives patients affected by this malignancy the chance for a full cure. The main goal of surgical therapy is to provide the local control of the disease and to secure long-term survival of the patient without reasonable functional and esthetic impairment. The recommended method of biopsy—excisional biopsy, as an initial diagnostic and, to some extent, therapeutic procedure—is performed under local anesthesia as an elliptical incision with visual clear margins of 1–3 mm and with some mm of subcutaneous tissue. The extent of radical excision of the primary tumor (or scar after excisional biopsy) is based on the histopathologic characteristics of the primary tumor and usually consists of 1–2 cm margins with primary closure. The philosophy behind conducted randomized clinical trials has been to find the most conservative surgical approach that is able to guarantee the same results as more demolitive treatment. This has been the background of the trials designed to define the correct margins of excision around a primary cutaneous melanoma. Much less definition can be dedicated to the surgical management of patients with non-cutaneous melanomas.