Basal Cell Carcinoma (BCC) is the most common skin cancer worldwide, with an incidence so high, that it is out of global cancer statistics.1 Over the last decades, its incidence has risen, and despite its low lethality, it can have an aggressive local behavior and it places a high burden on global health systems.2,3

Dermoscopy is a helpful diagnostic tool that has proven useful in BCC, with a sensitivity of 91% and a specificity of 95%.4,5 This favors earlier detection and treatment planning; still, histological confirmation remains the gold standard for its diagnosis.6–9 Nowadays, smaller BCCs are found more frequently, probably because of preventive care culture and technological advances. Small BCCs have been defined by some authors as those measuring less than 5mm, while BCCs lower than 3mm have been denominated very small BCCs.10–15 Regarding clinical presentation, small BCCs are more prevalent in younger men, prevail on the face, are often pigmented, and their most common histological subtype is nodular.11 Detection of initial tumoral stages is related to an easier treatment, with better cosmetic outcomes and less functional impact.10 Today, literature is clear on classic and non-classic dermoscopic criteria of BCC; however, few studies on dermoscopy of small BCCs have been performed, reporting that these BCCs can present both classic and non-classic dermoscopic features, with blue-gray dots and ovoid nests as main structures.11,12

Very small BCCs (vsBCCs) are even more incipient lesions, that could display different features due to an early phase of tumoral growth.14–18 Dermoscopy on these tumors has not been widely studied, therefore, there is a scarcity of medical literature reporting and comparing dermoscopic characteristics with larger BCCs. The aim of this study was to describe and compare dermoscopic features of BCCs measuring ≤3mm, with those from 3 to 10mm in diameter.

This was an analytical cross-sectional study conducted between January 2017 and December 2021 in Medellín, Colombia. Inclusion criteria comprehended patients with a histopathological diagnosis of BCC, who had dermoscopic pictures with 10× or 20× magnification. Cases of recurrent BCC and cases without patients consent for photographic analysis were excluded. Cases were retrospectively and prospectively selected from a Skin Cancer Referral Center. An institutional database with all diagnosed BCCs was examined, and cases that met eligibility criteria were included. Prospectively, new cases of histopathological confirmed BCC were examined and if eligible, included. The study size was determined by the total number of BCCs that met eligibility criteria and were diagnosed during the mentioned period. The study protocol was in concordance with the ethical guidelines of the Declaration of Helsinki. Institutional Review Board approval was obtained from Universidad Pontificia Bolivariana.

Two of the researchers were responsible for data and dermoscopic picture recollection. Two databases were created using Microsoft Excel and Microsoft PowerPoint, where information and pictures were organized. Dermoscopy was performed using a polarized device (DermLite DL4, 3 Gen, LLC, San Juan Capistrano, California, United States of America – FotoFinder ATBM, Bad Birnbach, Germany) and dermoscopic images were acquired with a high-resolution camera adapted to the dermoscopic device. Pictures were assessed by two independent observers for predefined dermoscopic features. In case of discordance, a third evaluation was made, and a consensus was achieved. Tumoral size was measured digitally, based on the largest diameter. BCCs were classified according to their size in three groups: 1) vsBCCs (measuring less than 3mm), 2) Small BCCs (from 3 to 5mm), and 3) Medium BCCs (from 5 to 10mm). The latter two were grouped as reference or control BCCs (from 3 up to 10mm) when compared to vsBCCs.

Demographic, clinical, histopathological and therapeutic features were obtained from medical records and pathology reports and included: age, gender, occupation, personal history of Non-Melanoma Skin Cancer (NMSC) or melanoma, Fitzpatrick skin phototype, signs of local photodamage, number of lesions per patient, size and location of the tumor, specific sublocation in case of facial tumors, primary lesion, predominant color (defined as color present in more than half of the lesion), the person that detected the lesion, time of evolution, histopathological subtype, tumoral depth, clinicopathological concordance, treatment modality, and in case of Mohs Micrographic Surgery (MMS) number of stages, histological subtype on surgery, and concordance with previous biopsy.

The following BCC dermoscopic criteria were analyzed: 1) Lack of pigmented network; 2) Vessels: arborizing vessels, Short-Fine Telangiectasias (SFT), hairpin, corkscrew, glomerular, dotted, comma and lineal irregular vessels, polymorphous vessels (defined as two or more morphologies), milky-red areas and red globules; 3) Pigmented structures: leaf-like structures, spoke-wheel-like structures, blue-gray globules, ovoid nests, concentric structures, and blue-gray dots; 4) Shiny White Structures (SWS): blotches and strands, rosettes, and streaks (orthogonal structures); 5) Scales: white or yellow; and 6) Other structures: ulceration, micro-erosions, multiple aggregated yellow globules (MAY globules), blue-whitish veil, and milia-like cysts.

Quantitative variables were presented as mean and Standard Seviations (SD), according to the normal distribution of variables evaluated with the Kolmogorov-Smirnov test. In the case of non-normality, medians and interquartile ranges were obtained. The size was the dependent variable, classified into three groups, as mentioned before. Dermoscopic features were compared between groups with the statistical tests Chi-Square or Fisher test, depending on the expected value (statistical significance, p<0.05). The database was exported to IBM SPSS Statistics 24.0 software for statistical analysis.

Dermoscopy has a high accuracy and precision in the diagnosis of BCC, which benefits an earlier suspicion of malignancy and favors the detection of smaller tumors. In this study, the authors assessed 326 BCCs of 196 patients. vsBCCs accounted for 81 of the tumors. They often had brown as the predominant color (39%) and showed commonly a nodular subtype on histopathology (93%) and rarely a superficial pattern (9%). Interestingly, aggressive subtypes had similar frequencies regardless of tumoral size. Most of the smaller lesions were located on the face and neck, in concordance with current literature;19,20 besides, as size increased, prevalence in other areas rose as well. These lesions were more likely to receive MMS, practiced in 48% of vsBCCs vs. 40% of reference BCCs; in 95% (37/39) of vsBCCs who underwent MMS it took more than 1 stage to obtain negative surgical margins.

On dermoscopy of vsBCCs, the presence of pigmented structures was the most frequent dermoscopic characteristic (83%), mainly blue-gray dots (67%), and was more frequent in these tumors when compared with larger BCCs. Conversely, vessels were less frequent in vsBCCs, notably SFT, as were SWS, scales, ulcerations, and micro-erosions. The most common vascular morphologies were SFT (52%) and arborizing vessels (33%). Of lesions displaying SFT, just 7% (3/42) corresponded to superficial histological subtype, 2% (1/42) to mixed subtype micronodular and infiltrative, and 91% (38/42) of them were nodular. This means that SFTs, in this study, were not present in the context of a superficial BCC.

On nodular vsBCCs (75/81) blue-gray dots were also the most frequent feature found in 68% (51/75). Vessels were found in 65% (49/75) of the tumors, mainly SFT in 51% (38/75), and arborizing vessels in 35% (26/75). High-risk histological subtypes were found in 6 very small lesions. Most of them displayed vessels as main dermoscopic feature (83%), mainly arborizing vessels (67%), followed by SFT (50%). Interestingly, in these tumors, blue-gray dots were not as common (33%).

On superficial vsBCCs (7/81), the most common feature was also the presence of pigmented structures in 86% (6/7), mainly blue-gray dots (57%), followed by ovoid nests and leaf-like structures (43% each). Vessels were found in 71% (5/7) of these lesions, and, interestingly, were polymorphous in all the cases, with glomerular morphology predominating 57% (4/7), followed by SFT 43% (3/7); however, arborizing vessels were not identified. Just one of these lesions presented micro-erosions.

Takahashi et al.10 published a study comparing BCCs ≤3mm (n=6) with BCCs from 4 to 6mm (n=11). Blue-gray dots and globules were present on 100% of the cases of the former group, and nests on 67%, in contrast to the present study, where they were found on 67%, 30%, and 24% of vsBCCs, respectively. Additionally, they found just 9% of lesions had blue-gray dots in the group from 4 to 6mm, contrary to the results, which showed they were present on 54% of reference BCCs. The main limitation of their study was the small size of the sample.

Sanchez-Martin et al.12 published a study on 100 BCCs < 5mm, divided into two groups, comparing vsBCCs (n=34) with small BCCs (n=66). The most frequent structure was SFT (78%), followed by blue-gray dots (55%). However, they did not find any statistically significant difference between very small and small BCCs, differing from the present results (Table 4).

Longo et al.13 compared BCCs <5mm with control lesions. They found small BCCs were more prevalent in younger patients, in contrast to the present results, since the authors did not find any association between age and tumoral size. The nodular pattern was also the more frequent subtype in their study, with an odds ratio of 3.4. They found two dermoscopic predictors of small BCCs: blue-gray dots and ovoid nests, however, these features had weak odds ratios and their confidence interval crossed the unity in both cases. Almost all dermoscopic features were observed equally in both groups, and the only statistically significant difference was a lower frequency of ulceration and micro-erosions in BCCs of <5mm.

Di Meo et al.11 collected 100 BCCs of <5mm from a database and evaluated global concordance between observers with low dermoscopic experience. They found a low level of concordance for some of the classic BCC criteria, and no concordance for almost all non-classic criteria. As seen in the present study, the presence of blue-gray dots, a non-classic feature, is key to detecting incipient lesions. This confirms the importance of always evaluating both classic and non-classic criteria, since the latter may correlate with an early tumoral stage.

The present study has some limitations. Cases were collected from a Skin Cancer Reference Center, which may alter patients’ demographic characteristics. Since it was conducted in Colombia, most phototypes ranged from I to IV, with less data on clearer and darker skin phototypes. It remains to be confirmed in larger studies with long-term follow-up, if early detection of very small lesions improves with dermoscopy, and the prognostic value that it may have.

In conclusion, on dermoscopy of vsBCCs (≤3mm), pigmented structures are more frequent, especially blue-gray dots, while vessels and SWS are less prevalent. Thus, when evaluating a lesion smaller than 3mm and suspicious for BCC, blue-gray dots and pigmented features must be actively sought, as its presence correlates with BCC. This study has robust evidence that may favor an earlier diagnosis in initial tumoral growth stages, rising the probability of acceptable better and functional outcomes after treatment.

None declared.

Camilo Arias-Rodriguez: Study concept and design; data collection, analysis and interpretation; writing of the manuscript; critical review of the literature; final approval of the final version of the manuscript.

Ana Maria Muñoz-Monsalve: Study concept and design; effective participation in the research guidance; critical review of important intellectual content; final approval of the final version of the manuscript.

Diana Cuesta: Study concept and design; data analysis and interpretation; writing of the manuscript; critical review of the literature; final approval of the final version of the manuscript.

Susana Mejia-Mesa: Study concept and design; data analysis and interpretation; writing of the manuscript; critical review of the literature; final approval of the final version of the manuscript.

Maria Soledad Aluma-Tenorio: Study concept and design; data analysis and interpretation; writing of the manuscript; critical review of the literature; final approval of the final version of the manuscript.

None declared.