JAAD ONLINE:NOTES & COMMENTS Reply to ‘‘Correlation of Basal Cell Carcinoma Subtype With Histologically Confirmed Subclinical Extension During Mohs Micrographic Surgery: A Prospective Multi-Center Study’’ To the Editor: We read with interest the study by Lim et al, 1 in which consecutive basal cell carcinomas (BCCs) treated with Mohs micrographic surgery (MMS) were evaluated. In the study, the subclinical tumor extension (SCE) was measured by assessing average stages to clear margins. Histologic subtype drift (HSD), defined as a change in basal cell carcinoma subtype (BCCS) from the time of the index biopsy to that at the time of the final stage of MMS, was also assessed. They found that superficial basal cell carcinoma (sBCC) and aggressive basal cell carcinoma (aBCC) exhibited similar and significantly greater SCE than other BCCSs and that sBCC was commonly the final marginal subtype when HSD was noted. 1 They contended that these results challenge the perception that sBCC is a low-risk BCCS because its degree of SCE akin to traditionally defined aBCCs demonstrates its ‘‘significant potential to be clinically occult.’’ Thus, they asserted that sBCCs merit com- plete margin clearance to minimize recurrence, and it is reasonable to consider MMS as potentially beneficial for their treatment. 1 We disagree with these conclusions because suggesting sBCCs to be treated as aBCCs runs counter to sBCC’s very indolent clinical behavior, superficial growth pattern, and reported high cure rates with alternative destructive treatment options that do not assess surgical margins. The SCE of sBCCs is primarily very superficial, whereas the SCE of aBCCs is commonly deeper, destructive, and associ- ated with perineural invasion. Their conclusion significantly deviates from Sexton BCC classification, MMS criteria, and national guidelines. 2 The presence of SCE of sBCCs and HSD of all BCCSs are well documented. Orengo et al, 3 in 1997, reported that 54.4% of sBCCs were ‘‘troublesome,’’ in that they required $3 MMS stages and exhibited ‘‘wide extensions beyond their clinical appearance.’’ They further noted that all BCCSs exhibit a high rate of HSD, with only a 42.7% correlation between the index biopsy of BCCSs and that observed at the final stage of MMS. 3 The optimal treatment options for BCCS are determined based on their cure rates, morbidity, the risk of complications, cosmesis, cost, the health status of patients, and other factors. They are not determined by any single histologic clinical charac- teristic. Cure rates with excision 4 and curettage techniques, 5 which may incompletely remove the SCE of sBCCs, have reported cure rates similar to those with MMS. There exists legitimate debate about the appropri- ateness of various treatments options for sBCC. To meaningfully compare MMS with other treatments, prospective randomized controlled trials, ideally eval- uating recurrence rates and other factors, would be required. Current evidence suggests that complete marginal clearance is not required to cure a substantial number of sBCCs. MMS likely has a select place among treatment options. However, for the reasons stated above, we contend that sBCCs do not merit treatment as aBCCs, and the routine use of MMS in the treatment of sBCCs merits reconsideration. Howard K. Steinman, MD, a Anthony Dixon, PhD, MBBS, b and Christopher B. Zachary, MBBS c From the Department of Surgery, Campbell Univer- sity School of Osteopathic Medicine, Lillington, North Carolina a ; Australasian College of Cuta- neous Oncology, Docklands, Victoria, Austral- ia b ; and Department of Dermatology, University of California, Irvine, Irvine, California. c Funding sources: None. IRB approval status: Not applicable. Correspondence and reprint requests to: Howard K. Steinman, MD, 2601 Dame Brisen Drive, Lewisville, TX 75056 E-mail: hksteinman@gmail.com Conflicts of interest None disclosed. REFERENCES 1. Lim GF, Perez OA, Zitelli JA, Brodland DG. Correlation of basal cell carcinoma subtype with histologically confirmed subclin- ical extension during Mohs micrographic surgery: a prospec- tive multi-center study. J Am Acad Dermatol. 2022;86(6): 1309-1317. https://doi.org/10.1016/j.jaad.2022.02.037. 2. NCCN Clinical Practice Guidelines in Oncology. Basal Cell Skin Cancer Version 1.2022. National Comprehensive Cancer Network (NCCN Guidelines). Accessed March 26, 2022. https://www. nccn.org/guidelines/guidelines-detail?category¼1&id¼1416 3. Orengo IF, Salasche SJ, Fewkes J, Khan J, Thornby J, Rubin F. Correlation of histologic subtypes of primary basal cell carcinoma and number of Mohs stages required to achieve a tumor-free plane. J Am Acad Dermatol. 1997;37(3):395-397. 4. Kiely JR, Patel AJ. A retrospective study of 694 basal cell carcinoma excisions to quantify deep margin documentation and clearance compared to histological type and surgical JAM ACAD DERMATOL NOVEMBER 2022 e147