Appropriate Use of Mohs Micrographic Surgery: A Survey of Australasian Mohs Dermatologists

Appropriate use criteria for Mohs Micrographic Surgery (MMS) were developed and published by the American Academy of Dermatology (AAD) and American College of Mohs Surgery (ACMS) in 2012 [1]. While Australian appropriate use consensus guidelines are yet to be developed, Medicare guidelines suggest that head, neck, genitalia, hand, digits, leg (below knee) or foot lesions should comprise 90% of MMS caseload [2]. This study aimed to survey Australian Mohs Dermatologists regarding the appropriate use of MMS in the management of basal cell carcinoma (BCC) and squamous cell carcinoma (SCC). An electronic questionnaire consisting of 171 clinical scenarios regarding the use of MMS in BCC and SCC management was developed, based on the appropriate use criteria published by the AAD and ACMS [1]. Anatomic sites were defined according to the published criteria [1, 3], as shown in Figure 1. All 77 Mohs Dermatologists registered with the Australasian College of Dermatologists were surveyed anonymously in August 2024. The survey was scored similarly to the AAD and ACMS appropriate use criteria [1]. Each clinical scenario was scored by participants using a 9-point scale (7–9, appropriate for MMS; 4–6, uncertain and MMS may be appropriate; 1–3 inappropriate for MMS). Consensus was considered to be achieved when 70% of participants rated a scenario in the same category The median score was used to define a final category of appropriateness when clear consensus was not reached. In total, 39 out of the 77 Mohs specialists completed the survey, giving a response rate of 51%. A majority of the clinical indications reached consensus (110/171; 64%), with 103 (60%) deemed appropriate and 7 (4%) deemed inappropriate by participants. Of the remaining indications (61/171; 36%) that did not reach consensus, 24 (14%) were uncertain, 18 (10.5%) inappropriate and 19 (11%) appropriate, based on the median scores. There was no significant difference between the proportion of BCC (19/63; 30%) and SCC (42/108; 38%) indications that did not reach consensus (Chi-Squared value = 0.64; p = 0.42). The results regarding the appropriate use of MMS in the treatment of BCC and SCC are summarised in Tables 1 and 2, respectively. Results were in broad agreement with the AAD and ACMS guidelines [1]. There was a strong consensus supporting the use of MMS for BCC and SCC located on the head and neck, hands, feet, ankles, genitalia and pre-tibial sites. Similarly, there was more uncertainty regarding the use of MMS at other sites on the trunk and extremities (excluding hands, feet ) [1]. However, in comparison to AAD and ACMS guidelines [1], participants were more conservative in their opinion regarding the appropriate use of MMS at sites on the trunk and extremities (excluding hands, feet and ankles), with a greater number of clinical scenarios being considered inappropriate or uncertain. For example, a large (> 2 cm) nodular BCC in immunocompetent patients at sites on the trunk and extremities (excluding hands, feet and ankles) is considered appropriate for MMS under AAD and ACMS guidelines (appropriateness score of 7) [1]. However, Australian Mohs Dermatologists surveyed considered the use of MMS in this scenario to be less appropriate (appropriateness score of 4, uncertain use case for MMS). There was a trend for MMS to be considered more appropriate when lesions were larger and recurrent, if aggressive histological features were present, or in immunocompromised patients. A potential limitation of the study was responder bias. Furthermore, as the survey was conducted anonymously, it is uncertain whether participants from particular states were over- or under-represented. Nevertheless, anatomic site is a key indicator of appropriate MMS use, and analysis of Medicare item number data has shown little or no differences in the anatomic sites of MMS use between states [2]. In conclusion, our results suggest that Australasian Mohs Dermatologists are in agreement with the AAD and ACMS appropriate use criteria, but are more selective and conservative in their opinion regarding the use of MMS at trunk and proximal extremity sites. The data are consistent with previous studies which show that 98% of MMS in Australia is appropriately performed at the head and neck, hands, feet, ankles, genitalia and pre-tibial sites [2, 4], comparing favourably with experience overseas [3, 5, 6]. This survey data may provide a framework for the development of Australasian appropriate use consensus guidelines in the future. The authors declare nothing to report. The authors declare nothing to report. The authors declare no conflicts of interest. The data that support the findings of this study are available from the corresponding author upon reasonable request.