Dermoscopy is an accessible, relatively simple, noninvasive diagnostic technique widely used by dermatologists for the diagnosis of basal cell carcinoma (BCC). Its use for presurgical tumor delimitation has improved complete excision rates in conventional surgery.1 The use of dermoscopy in Mohs micrographic surgery (MMS) has been proposed to help reduce the resulting surgical defect by improving the delineation of lateral margins,2 but the literature is inconsistent regarding whether this translates into a lower number of MMS stages required to achieve tumor-free margins.3–6

The aim of our study was to determine whether the use of dermoscopy (DSCP) for presurgical delimitation of basal cell carcinoma helps reduce the resulting lateral margins and the number of MMS stages compared with clinical tumor delimitation alone.

We designed an observational, nonrandomized study of clinical practice in which data from all patients undergoing surgery for basal cell carcinoma (BCC) of the cephalic pole by MMS were prospectively collected from May through September 2023 in the Dermatology Department of a monographic oncologic center specialized in skin cancer.

The center's standard MMS surgical procedure consists of debulking by shaving the clinically visible tumor, followed by curettage of the resulting wound and successive stages, approximately 2mm each, required to obtain tumor-free margins. When histologically the tumor involves only the tumor bed and not the lateral margin, skin from the margin is not included in the next stage.

The following independent variables were collected: age, sex, tumor location, tumor type (primary, excised with involved margins without specification of whether they were lateral or deep, or recurrent), clinical tumor size (in millimeters), and histologic subtype of BCC categorized as high risk (infiltrative, micronodular, and basosquamous) or low risk (nodular and superficial).

The primary outcome variable was the number of MMS stages required and the lateral defect in millimeters needed to achieve tumor-free margins.

In addition, the difference in millimeters between clinical evaluation and clinical evaluation complemented with dermoscopy of tumor size prior to MMS was assessed. Dermoscopy was used at the surgeon's discretion in a nonrandomized manner, and any changes to the previous marking performed by visual inspection were recorded. Dermoscopic inspection was performed using a handheld Dermlite DL200 Hybrid dermatoscope. Finally, subjective factors associated with the use of dermoscopy for preoperative tumor delimitation were analyzed.

Continuous variables were tested for normal distribution using the Kolmogorov–Smirnov test. Because they did not follow a normal distribution, the Mann–Whitney U test was used for comparison of means. For categorical variables, frequency and percentage were recorded, and comparisons were performed using the Pearson chi-square test (or Fisher exact test when appropriate). Statistical analysis was performed using IBM SPSS version 22, and statistical significance was set at P<.05.

According to the selection criteria, a total of 98 patients were identified. Clinical and dermoscopic delimitation was performed in 64 (65.3%) tumors, whereas 34 (34.7%) tumors were delimited clinically only (Table 1). A total of 59 primary tumors, 8 tumors excised with positive margins with clinical persistence, and 31 recurrent tumors were included. There were 45 tumors with high-risk histology (35 [35.7%] infiltrative, 8 [8.2%] micronodular, and 2 [2.1%] basosquamous) and 53 low-risk tumors (48 [49%] nodular and 5 [5.1%] superficial).

No differences were observed in the number of MMS stages; however, there were significant differences in the final lateral margin. Thirteen (20.3%) tumors delimited with dermoscopy required ≤4mm of margin vs 1 (2.9%) of those delimited only by visual inspection (P=.03). Among dermoscopically delimited cases, 10 (25.6%) low-risk tumors and 3 (12%) high-risk tumors were resolved with ≤4mm margins, whereas among tumors delimited only by visual inspection, 19 (95%) high-risk tumors and all low-risk tumors (14) required >4mm (P=.03) (Table 2).

Among the 64 cases delimited with dermoscopy, differences compared with clinical marking were observed in 14 (21.9%) tumors. When differences were present, 13 (92.9%) cases were resolved in a single stage, whereas when there were no differences, 34 (68%) tumors were resolved in 1 stage; however, this difference was not statistically significant (P=.089). Notably, all low-risk tumors (11) were resolved in a single stage when dermoscopic marking differed from clinical marking, although this finding did not reach statistical significance (P=.29). These results are shown in Table 3 of the supplementary material.

Dermoscopy was used significantly more frequently in women vs men (37 [57.8%] vs 27 [42.2%]; P=.007). Although not reaching statistical significance, dermoscopy was also used more frequently in low-risk histologic subtypes than in high-risk ones (39 [60.9%] vs 25 [31.1%]; P=.06).

In this study of 98 patients, dermoscopy was shown to be useful in reducing the surgical defect obtained after MMS in low-risk tumors. However, it did not reduce the number of stages or provide benefits for high-risk tumors.

MMS allows visualization of almost the entire surgical margin, enabling minimization of excision of healthy peritumoral tissue and significantly reducing tumor recurrence.7

Several studies have evaluated the usefulness of preoperative dermoscopy for optimizing MMS. Many have concluded that it does not provide significant differences in the number of MMS stages required to achieve negative margins,3,8–11 whereas 2 studies did find that dermoscopy was associated with a significant reduction in the number of stages.5,6 However, there is considerable heterogeneity in study design, making it difficult to extrapolate the results. Many studies include small patient series and often do not specify tumor type (primary and/or recurrent) or the histologic subtype evaluated. A summary of these studies can be found in Table 4 of the supplementary data.

A recent meta-analysis by Litaiem et al.4 including 6 former studies concluded that there were no significant differences between visual inspection and dermoscopy in achieving tumor-free margins in the first stage; however, significantly smaller lateral margins were obtained in tumors delimited with dermoscopy. The included studies involved both primary and recurrent tumors, and it was not always specified whether dermoscopy and surgery were performed by the same operator. Our results are consistent with the conclusions of this meta-analysis. It should be noted that both MMS and dermoscopy are highly operator-dependent techniques, which may influence study outcomes.

Although our series did not show a reduction in the total number of MMS stages between groups, we observed that when dermoscopic delimitation resulted in changes to the clinical marking of tumors, those tumors tended to be resolved in a single MMS stage, particularly in low-risk subtypes. These findings might have reached statistical significance with a larger sample size or by analyzing only low-risk subtypes.

In our study, the operator tended to use dermoscopy more frequently in low-risk subtypes (superficial and nodular), probably reflecting clinical experience that these subtypes often display more dermoscopically assessable features than high-risk histologic subtypes, which tend to have greater subclinical extension. In addition, dermoscopic evaluation was performed significantly more often in women, possibly reflecting a gender-related bias toward greater attention to preserving healthy tissue to improve aesthetic outcomes.

The limitations of our study include the small sample size and lack of randomization. In addition, tumor types were heterogeneous, as both primary tumors and recurrences or tumors previously excised with involved margins were included. In the latter 2 groups, the presence of scars may complicate dermoscopic evaluation. Of note, clinical inspection and dermoscopic evaluation of each case were always performed by the same observer with experience in dermoscopy.

Dermoscopy is a useful noninvasive tool for delimiting nodular and superficial basal cell carcinomas and helps reduce the resulting surgical defect and preserve healthy tissue in patients undergoing MMS. Tumor delimitation in high-risk basal cell carcinomas should be optimized using other techniques, since the main factor determining surgical complexity and the number of MMS stages is involvement of the deep margin.

None declared.

None declared.