In total, 80 patients (52 women and 28 men) with histopathologically confirmed 151 BCCs, all located on the head and neck region, were included in the study. Twelve patients with 18 lesions, clinically suspected to be BCC, were excluded because of different histopathological diagnoses (mainly adnexal tumors or squamous cell carcinoma). One patient was excluded because of poor quality of dermoscopic images.

All participants had Fitzpatrick skin phototypes I–III. The BCCs were categorized into two clinical subtypes: nodular (n = 90; 59.6%) and superficial (n = 61; 40.4%). The majority of the tumors were nonpigmented (n = 119; 78.8%). The average tumor size measured 8.3 ± 6 mm. Detailed demographic and clinical characteristics of the patients are summarized in Table 1.

Head and neck BCCs under PD most frequently showed vascular structures, including arborizing vessels (52.3%) and short fine telangiectasias (45.7%), occurring on red-white homogeneous areas (40.4%) with ulcerations or micro-ulcerations (33.8%). The occurrence frequencies of these and other dermoscopic features are presented in detail in Table 2.

Under UVFD, BCCs appeared as dark silhouettes (78.8%) with an interrupted follicle pattern (53.0%), lacking follicular fluorescence observed in the area surrounding the tumor—either blue-green (44.4%) or pink-orange (39.7%). A considerable number of lesions showed well-demarcated borders (43%). Table 2 presents the occurrence frequencies of these findings.

A total of 61.6% (93/151) of the analyzed BCCs on the head and neck were located within the H-zone. Among these, 65.6% (61/93) were classified as nodular, while 34.4% (32/93) were superficial. The majority of tumors in this region (86%, 80/93) were non-pigmented, whereas 14% (13/93) exhibited pigmentation. Regarding tumor size, 24.7% (23/93) measured between 0–4 mm in diameter, 53.8% (50/93) were within the 5–10 mm range, and 21.5% (20/93) exceeded 10 mm. One large BCC extended across both the H-zone and non-H-zone.

No statistically significant difference was found in the size or clinical subtype between tumors located in the H-zone and non-H-zone. However, the non-pigmented subtype was significantly more frequent in the H-zone (p = 0.008).

Under PD, ulcerations/micro-ulcerations (40.9% vs. 23.7%, p = 0.021) and hemorrhages (24.7% vs. 11.9%, p = 0.033) were observed more frequently in the H-zone compared to the non-H-zone. Similarly, under UVFD, a higher prevalence of erosions/ulcerations (30.1% vs. 15.3%, p = 0.019) and blue-fluorescent fibers (14% vs. 3.4%, p = 0.009) was noted in the H-zone. Moreover, lack of blue-green fluorescence (51.6% vs. 32.2%, p = 0.019) within the tumor was observed more frequently in the H-zone.

Table 2 and Figs. 1 and 2 present the clinical and dermoscopic characteristics of BCCs by location in the H-zone or non-H-zone.

Polarized light dermoscopy (PD) presentation of basal cell carcinoma (BCC) in the H-zone of the face including BCC (a, c) on the nose and (b) in the oral region. d–f Corresponding images in ultraviolet-induced fluorescence dermoscopy (UVFD). d Dark silhouette, ulceration (red arrow), pink-orange follicular fluorescence at the periphery of the tumor (yellow arrowheads), blue-green follicular fluorescence at the periphery of the tumor (pink arrowheads), absence of both types of fluorescence within the BCC, follicle pattern in the surrounding skin (green arrowheads), interrupted follicle pattern within the lesion, follicular plugging (orange arrow). e Dark silhouette, ulceration (red arrow), blue fluorescent fibers (yellow arrowheads), follicle pattern in the surrounding skin (green arrowheads), interrupted follicle pattern within the lesion. f Dark silhouette, erosion (red arrow), arborizing vessels (yellow arrow), follicle pattern in the surrounding skin (green arrowheads), interrupted follicle pattern within the lesion, blue-green follicular fluorescence at the periphery of the tumor (pink arrowheads), absence of this type of fluorescence within the BCC

PD presentation of BCC in the a–c non-H-zone of the face including BCC (a) on the neck and (b, c) on the cheek. d–f Corresponding images in UVFD. d Dark silhouette, arborizing vessel (yellow arrow), blue-green follicular fluorescence at the periphery of the tumor (pink arrowheads), absence of this type of fluorescence within the BCC. e Dark silhouette, follicle pattern in the surrounding skin (green arrowheads), interrupted follicle pattern within the lesion, blue-green follicular fluorescence at the periphery of the tumor (pink arrowheads), absence of this type of fluorescence within the BCC. f Dark silhouette, pink-orange follicular fluorescence at the periphery of the tumor (yellow arrowheads), absence of this type of fluorescence within the BCC, follicle pattern in the surrounding skin (green arrowheads), interrupted follicle pattern within the lesion

The frequency of pigmented BCCs varied significantly (p < 0.001) according to anatomical site. All of the scalp BCCs were pigmented followed by tumors located in the forehead region (42.1%), eyes and periorbital region (22.2%), rest of the face (18.2%), cheeks (15.8%), oral region (12.5%), nose and paranasal region (11.4%). Lower frequencies were noted in the temple or ears and periauricular region (each 9%) while no pigmented BCCs were detected on the neck.

PD and UVFD revealed several significant differences in the dermoscopic presentations of BCCs across specific anatomical sites. Under PD, red-white homogeneous areas (p = 0.045) were most frequently observed on the temple (90.9%), followed by the neck (50.0%), nose and paranasal region (45.7%), rest of the face (45.5%), cheek (42.1%), and oral region (31.3%). Blue-gray globules showed the highest occurrence (p = 0.004) on the scalp (66.7%), with lower frequencies on the forehead (21.0%), ears and periauricular region (18.2%), and temple (18.2%). Moreover, the blue-white veil (p = 0.004)—a feature often associated with melanoma—was exclusively seen in the ears and periauricular region with an 18.2% occurrence at these sites.

Under UVFD, an interrupted follicle pattern (p = 0.012) was most frequently observed in the oral region (75.0%), followed by the nose and paranasal region (71.4%), forehead (57.9%), and cheeks (52.6%). Erosions or ulcerations (p = 0.04) were most common on the neck (50.0%), followed by the ears and periauricular region (45.5%), nose and paranasal region (40.0%), scalp (33.3%), and oral region (31.3%). A lack of blue-green fluorescence (p < 0.001) showed the highest occurrence in the neck (75%), nose and paranasal region (74.3%), and oral region (62.5%). Similarly, the absence of pink-orange fluorescence (p = 0.001) was most frequent in the nose and paranasal region (65.7%) and oral region (56.3%).

Tables 3 presents the frequencies of PD features across various anatomical locations, while Table 4 summarizes the distribution of UVFD findings. Examples of BCCs in the nose and paranasal region are presented in Fig. 3, while those in the oral region are shown in Fig. 4.

PD presentation of BCC in the a, b nose and c paranasal region. d–f Corresponding images in UVFD. d Dark silhouette, arborizing vessel (yellow arrow), pink-orange follicular fluorescence at the periphery of the tumor (red arrowheads), blue-green follicular fluorescence at the periphery of the tumor (pink arrowheads), absence of both types of fluorescence within the BCC, follicle pattern in the surrounding skin (green arrowheads), interrupted follicle pattern within the lesion. e Dark silhouette, arborizing vessel (yellow arrow), follicle pattern in the surrounding skin (green arrowheads), interrupted follicle pattern within the lesion. f Dark silhouette, arborizing vessel (yellow arrow), pink-orange follicular fluorescence at the periphery of the tumor (red arrowheads), absence of this type of fluorescence within the BCC, follicle pattern in the surrounding skin (green arrowheads), interrupted follicle pattern within the lesion

a, b PD presentation of BCC in the oral region. c, d Corresponding images in UVFD. c Dark silhouette, black globules (red arrows), pink-orange follicular fluorescence at the periphery of the tumor (yellow arrowheads), absence of this type of fluorescence within the BCC. e Dark silhouette, arborizing vessel (yellow arrow), pink-orange follicular fluorescence at the periphery of the tumor (pink arrowheads), absence of this type of fluorescence within the BCC, follicle pattern in the surrounding skin (green arrowheads), interrupted follicle pattern within the lesion