Comment
We presented 5 cases of MMS in Japanese patients with BCC. More than 7000 new cases of nonmelanoma skin cancer occur every year in Japan.3 Only 0.04% of these cases—the 5 cases presented here—were treated with MMS in Japan in 2020 and 2021, in contrast to 25% in the United States in 2006.2
MMS vs Other BCC Treatments—Mohs micrographic surgery offers 2 distinct advantages over conventional excision: an improved cure rate while achieving a smaller final defect size, generally leading to better cosmetic outcomes. Overall 5-year recurrence rates of BCC are 10% for conventional surgical excision vs 1% for MMS, while the recurrence rates for SCC are 8% and 3%, respectively.5 A study of well-demarcated BCCs smaller than 2 cm that were treated with MMS with 2-mm increments revealed that 95% of the cases were free of malignancy within a 4-mm margin of the normal-appearing skin surrounding the tumor.6 Several articles have reported a 95% cure rate or higher with conventional excision of localized BCC,7 but 4- to 5-mm excision margins are required, resulting in a greater skin defect and a lower cure rate compared to MMS.
Aggressive subtypes of BCC have a higher recurrence rate. Rowe et al8 reported the following 5-year recurrence rates: 5.6% for MMS, 17.4% for conventional surgical excision, 40.0% for curettage and electrodesiccation, and 9.8% for radiation therapy. Primary BCCs with high-risk histologic subtypes has a 10-year recurrence rate of 4.4% with MMS vs 12.2% with conventional excision.9 These findings reveal that MMS yields a better prognosis compared to traditional treatment methods for recurrent BCCs and BCCs of high-risk histologic subtypes.
The primary reason for the excellent cure rate seen in MMS is the ability to perform complete margin assessment. Peripheral and deep en face margin assessment (PDEMA) is crucial in achieving high cure rates with narrow margins. In WLE (Figure 1), vertical sectioning (also known as bread-loafing) does not achieve direct visualization of the entire surgical margin, as this technique only evaluates random sections and does not achieve PDEMA.10 The bread-loafing method is used almost exclusively in Japan and visualizes only 0.1% of the entire margin compared to 100% with MMS.11 Beyond the superior cure rate, the MMS technique often yields smaller final defects compared to WLE. All 5 of our patients achieved complete tumor removal while sparing more normal tissue compared to conventional WLE, which takes at least a 4-mm margin in all directions.
Barriers to Adopting MMS in Japan—There are many barriers to the broader adoption of MMS in Japan. A guideline of the Japanese Dermatological Association says, MMS “is complicated, requires special training for acquisition, and requires time and labor for implementation of a series of processes, and it has not gained wide acceptance in Japan because of these disadvantages.”3 There currently are no MMS training programs in Japan. We refute this statement from the Japanese Dermatological Association because, in our experience, only 1 surgeon plus a single histotechnician familiar with MMS is sufficient for a facility to offer the procedure (the lead author of this study [S.S.] acts as both the surgeon and the histotechnician). Another misconception among some physicians in Japan is that cancer on ethnically Japanese skin is uniquely suited to excision without microscopic verification of tumor clearance because the borders of the tumors are easily identified, which was based on good cure rates for the excision of well-demarcated pigmented BCCs in a Japanese cohort. This study of a Japanese cohort investigated the specimens with the conventional bread-loafing technique but not with the PDEMA.12
Eighty percent (4/5) of our patients presented with nodular BCC, and only 1 required a second stage. In comparison, we also treated 16 White patients with nodular BCC with MMS during the same period, and 31% (5/16) required more than 1 stage, with 1 patient requiring 3 stages. This cohort, however, is too small to demonstrate a statistically significant difference (S.S., unpublished data, 2020-2022).
A study in Singapore reported the postsurgical complication rate and 5-year recurrence rate for 481 tumors (92% BCC and 7.5% SCC). The median follow-up duration after MMS was 36 months, and the recurrence rate was 0.6%. The postsurgical complications included 11 (2.3%) cases with superficial tip necrosis of surgical flaps/grafts, 2 (0.4%) with mild wound dehiscence, 1 (0.2%) with minor surgical site bleeding, and 1 (0.2%) with minor wound infection.13 This study supports the notion that MMS is equally effective for Asian patients.
Awareness of MMS in Japan is lacking, and most Japanese dermatologists do not know about the technique. All 5 patients in our case series asked their dermatologists about alternative treatment options and were not offered MMS. In each case, the patients learned of the technique through internet research.
The lack of insurance reimbursement for MMS in Japan is another barrier. Because the national health insurance does not reimburse for MMS, the procedure is relatively unavailable to most Japanese citizens who cannot pay out-of-pocket for the treatment and do not have supplemental insurance. Mohs micrographic surgery may seem expensive compared to WLE followed by repair; however, in the authors’ experience, in Japan, excision without MMS may require general sedation and multiple surgeries to reconstruct larger skin defects, leading to greater morbidity and risk for the patient.
Conclusion
Mohs micrographic surgery in Japan is in its infancy, and further studies showing recurrence rates and long-term prognosis are needed. Such data should help increase awareness of MMS among Japanese physicians as an excellent treatment option for their patients. Furthermore, as Japan becomes more heterogenous as a society and the US Military increases its presence in the region, the need for MMS is likely to increase.
Acknowledgments—We appreciate the proofreading support by Mark Bivens, MBA, MSc (Tokyo, Japan), as well as the technical support from Ben Tallon, MBChB, and Robyn Mason (both in Tauranga, New Zealand) to start MMS at our clinic.