Clinical distribution patterns and histopathological features of 2016 cases of basal cell carcinoma: a retrospective study from Southwest China

Abstract

Background

To investigate the clinical distribution patterns and clinicopathological characteristics of basal cell carcinoma (BCC) in Southwest China.

Methods

A retrospective analysis was conducted among 2016 patients diagnosed with BCC between April 2003 and May 2025. The study focused on lesion locations, facial distribution patterns, presentations of multiple BCCs, and histopathological features of BCC.

Results

A total of 2016 patients with 2138 BCC lesions were included, comprising 881 males (43.70%) and 1135 females (56.30%). The median age at initial diagnosis was 65 years (range, 17–101 years). Only 70 (3.50%) patients were younger than 35 years, whereas 663 (32.89%) were older than 70 years. The incidence of BCC increased with age from the fifth to the eighth decade of life. Most lesions were located on the head/face (88.59%, 1894), and 80.64% (1724) occurred on the faces. The nose/perinasal area was the most common facial subregion (31.15%, 666), followed by the cheeks (20.91%), indicating a midface predilection. Clinically, nodular/ulcerative presentations predominated (65.20%, 1394). Histopathologically, the nodular cystic subtype was most common (71.94%, 1538). Multiple tumors (two to ten lesions) were observed in 36 patients, including three cases with basal cell nevus syndrome. Surgical resection was performed in 97.82% (1972) of patients, while Mohs micrographic surgery was used in 25 (1.24%) cases. The 5-year recurrence rate was 4.10%.

Conclusions

BCC predominantly affects older adults, with an increasing incidence in those aged 50–80 years, and shows a striking predilection for sun-exposed midfacial sites. Nodular/ulcerative lesions are the predominant clinical presentation, and nodular cystic type is the most common histological subtype. Surgery remains the mainstay of treatment; although recurrences were infrequent, their distribution supports risk-adapted management and long-term follow-up.

Introduction

Basal cell carcinoma (BCC) is the most prevalent form of non-melanoma skin cancer (NMSC) worldwide [1]. Its occurrence varies significantly by geographic region but is characterized by a steady increase globally, with an estimated annual increase of approximately 7% in diagnosed cases [2, 3]. BCC is most common among individuals with fair skin, who face an approximate lifetime risk of 30% [4]. Prolonged ultraviolet (UV) exposure is the main environmental risk factor, causing cumulative cellular damage that can lead to carcinogenesis [1].

The clinical significance of BCC stems largely from its potential for destruction of local tissue [5, 6]. Although BCCs possess exceedingly rare metastatic potential, untreated or aggressively growing BCCs can cause substantial functional impairment and significant aesthetic disfigurement, especially given that more than 70% of BCCs occur on the faces. Extensive lesions and certain aggressive subtypes are associated with a high recurrence rate, compounding the risk of tissue damage and morbidity despite generally low mortality. Early detection and appropriate management are, therefore, crucial to minimize local destruction, reduce the risk of recurrence, and preserve function and cosmesis [7].

Most previous studies have primarily focused on pathological classification and treatment methods. In this study, we retrospectively analyzed 2016 patients with histopathologically confirmed BCC treated at three tertiary centers in Southwest China, with the aims of characterizing the anatomical distribution patterns of BCC lesions and the clinicopathological/histopathological features, with particular attention to facial lesions and patients with multiple BCCs.

Materials and methods

In this retrospective study, a total of 2016 patients diagnosed with BCC between April 2003 and May 2025 were included. The patient cohort was predominantly sourced from the Department of Dermatology at the First Affiliated Hospital of Army Medical University, with a smaller portion derived from the Department of Dermatology at Yongchuan Hospital of Chongqing Medical University and the Department of Dermatology and Rheumatology at Xinqiao Hospital of Army Medical University, representing the population of Southwest China. Demographic and clinical data, including age, sex, residential area (rural vs. urban), lesion location, clinical presentation, histopathological subtype and treatment modality were systematically extracted from the electronic medical records and the histopathology reporting system. The diagnosis and histopathological subtype were obtained by reviewing the official pathology reports recorded in the histopathology information system, and all original slides were re-reviewed by dermatopathology specialists at the respective institutions, without centralized cross-hospital slide re-review.

Inclusion and exclusion criteria

The inclusion criteria were as follows: (1) Histopathologically confirmed primary BCC based on consensus classification by recognized dermatopathologists and contemporary international guidelines, with standardized subtype definitions to ensure diagnostic reproducibility[8, 9]. (2) Availability of complete clinical data on age, sex, place of residence, anatomical site, clinical presentation, and histopathological subtype. (3) Treatment and/or follow-up performed at one of the participating dermatology departments.

The exclusion criteria were as follows: (1) Lesions with an uncertain histopathological diagnosis. (2) Non-BCC skin tumors or metastatic lesions. (3) Those with duplicate records. (4) Cases with missing key clinical information that precluded reliable classification. For analyses of anatomic distribution and histopathological subtypes, only the first primary BCC per patient was considered, and patients with recurrent BCC were included in the treatment and follow-up analyses but were not counted repeatedly in the primary distribution analyses.

In accordance with the Declaration of Helsinki, the study was approved by the Ethics Committee of the First Affiliated Hospital of Army Medical University No. (B) KY2025151. Because only anonymized data extracted from existing medical records and the histopathological diagnosis system were used and no direct patient contact occurred, the Ethics Committee waived the requirement for written informed consent to participate; written informed consent was obtained only from patients whose clinical photographs are published in this article.

Statistical analysis

All data analyses were performed using SPSS software (version 25.0; SPSS, Inc., Chicago, IL, USA). Continuous variables are presented as the means ± standard deviations or medians with ranges, whereas categorical variables are expressed as frequencies and percentages. Group comparisons of continuous variables were performed using independent-samples t tests or Mann–Whitney U tests, as appropriate. Categorical variables were compared using χ² tests or Fisher’s exact tests when expected cell counts were < 5. Recurrence-free survival (RFS) was estimated using the Kaplan–Meier method, with time calculated from the date of primary surgery to the date of first histologically confirmed local recurrence or to the date of last follow-up, and differences between groups were assessed using the log-rank test. A two-sided P < 0.05 was considered statistically significant.

Results

Demographic characteristics

A total of 2016 patients were included in the study, including 881 (43.70%) males and 1135 (56.30%) females. The median age at first diagnosis was 65 years (range, 17–101 years). Patients aged ≤40 years accounted for 6.40% (129/2016 cases), and the proportion of those aged ≥71 years reached 32.89% (663/2016 cases). Overall, the incidence of BCC increased with age in individuals from the fifth through the eighth decades of life. Only 3.50% (70/2016) patients were younger than 35 years. The incidence rate ratio of BCC among patients aged<40, 40–60, and >60 years was approximately 1:5:10. Most patients were from rural areas (1553/2016, 77.03%), and the ratio of patients from rural and urban areas was approximately 3.4:1 (Table 1).

Table 1.

Age, sex, and residential area distributions of 2016 BCC patients

Index	Cases (%)
Gender
Male	881 (43.70%)
Female	1135 (56.30%)
Age*
≤ 40	129 (6.40%)
41–50	224 (11.11%)
51–60	430 (21.33%)
61–70	570 (28.27%)
≥ 71	663 (32.89%)
Residential areas
Rural	1553 (77.03%)
Urban	463 (22.97%)

^*The age at which BCC was first diagnosed

Clinical distribution pattern

2016 BCC patients with a total of 2138 lesions were included in the analysis. Nearly 90% of lesions were located on the head/face region (1894/2138, 88.59%), and 80.64% (1724/2138) involved the faces. The nose/perinasal area was the most common facial subregion (666/2138, 31.15%), followed by the cheeks (447/2138, 20.91%) and the periocular/eyebrow region (295/2138, 13.80%), indicating a midface predilection (Fig. 1). Lesions on the upper limbs were rare (12/2138, 0.56%). The complete site distribution is shown in Table 2.

Fig. 1.

Schematic diagram of the clinical distribution pattern of facial BCC. The facial map depicts the probability distribution of BCC involvement. The five-layered contours correspond to 99%, 80%, 70%, 45%, and 25% probability regions, respectively. Darker color intensity indicates areas more frequently involved (higher probability of lesion distribution), illustrating the predominance of lesions in the midface region, particularly the nose/perinasal area, cheeks and periorbital regions

Table 2.

Anatomical distribution, histopathological subtypes and clinical classifications of 2138 BCC lesions

Anatomical site	Cases (%)	Histopathological subtype	Cases (%)
Head	1894 (88.59%)	Nodular cystic	1538 (71.94%)
Scalp	109 (5.10%)	Adenoid	96 (4.49%)
Frontal/temporal	189 (8.84%)	Micronodular	89 (4.16%)
Periocular/eyebrow	295 (13.80%)	Infiltrative	253 (11.83%)
Cheek	447 (20.91%)	Morpheaform (sclerosing)	7 (0.33%)
Nose/perinasal	666 (31.15%)	Keratinizing	53 (2.48%)
Lips	80 (3.74%)	Basosquamous (Variant)	8 (0.37%)
Lower jaw/chin	47 (2.20%)	Pigmented	6 (0.28%)
Ear	61 (2.85%)	Superficial	81 (3.79%)
Neck	20 (0.94%)	Rare	5 (0.23%)
Back	28 (1.31%)	Clear cell	2 (0.09%)
Chest/abdomen	88 (4.12%)	Clinical classification
Genital organ	39 (1.82%)	Nodular/ulcerative	1394 (65.20%)
Legs	57 (2.67%)	Diffuse (infiltrative and sclerotic)	130 (6.08%)
Arms	12 (0.56%)	Superficial (multiple)	459 (21.47%)
		Pigmented	144 (6.74%)
		Pinkus fibroepithelioma	11 (0.51%)
Total	2138 (100%)	Total	2138 (100%)

Rare histological variants include keratinizing and other low-frequency BCC patterns not otherwise classified in the main subtypes

Clinical subtype classification

Table 2 presents the clinical and pathological classification characteristics of all the lesions. The most common type of BCC clinical classification was nodular/ulcerative (1394/2138, 65.20%) (Fig. 2A–C). The second most common type was superficial (multiple) (459/2138, 21.47%) (Fig. 2D). The percentages of diffuse (infiltrative and sclerotic) (Fig. 2E) and pigmented types (Fig. 2F) were 6.08% (130/2138) and 6.74% (144/2138), respectively, and the Pinkus fibroepithelioma type was the least common (11/2138, 0.51%) (Fig. 2G).

Fig. 2.

Clinical classification of BCC. A–C Nodular/ulcerative BCC presents as a pearly, dome-shaped nodule with telangiectasia and may be ulcerated, with rolled borders. D Superficial BCC presents as erythematous, scaly, thin plaques with well-defined borders. E Diffuse (infiltrative and sclerotic) BCC presents as poorly demarcated, infiltrative lesions with indistinct borders, showing subtle erythema or pale plaques that may extend beyond visible margins. F Pigmented BCC presents as a nodular or ulcerated lesion with brown/black pigmentation. G Pinkus fibroepithelioma BCC presents as a flesh-colored, pedunculated or polypoid nodule with a smooth surface

The most frequently observed histopathological feature was a nodular cystic BCC (1538/2138, 71.94%) (Fig. 3A). Second only to the nodular cystic type was infiltrative BCC (253/2138, 11.83%) (Fig. 3B). This was followed by the adenoid (Fig. 3C), micronodular (Fig. 3D), and superficial types (Fig. 3E), accounting for 4.49% (96/2138), 4.16% (89/2138), and 3.79% (81/2138), respectively. Other histopathological subtypes collectively accounted for 3.79% (81/2138), including keratinizing, morpheaform (sclerosing), basosquamous (Variant), clear cell, pigmented and other rare BCC variants.

Fig. 3.

Histopathological classification of BCC. A Nodular cystic BCC (hematoxylin and eosin [H&E], original magnification × 40) is characterized by well-circumscribed basaloid tumor nodules with cystic spaces. B Infiltrative BCC (H&E, × 100) is characterized by thin strands of tumor cells infiltrating the dermis. C Adenoid BCC (H&E, × 100) exhibits a reticulated growth pattern with basaloid tumor islands forming lace-like or gland-like structures. D Micronodular BCC (H&E, × 100) is characterized by small tumor nests with infiltrative growth patterns. E Superficial BCC (H&E, × 100) is characterized by nests of basaloid cells attached to the undersurface of the epidermis with peripheral palisading, confined to the papillary dermis

Features of patients with multiple BCCs

Among the 2016 BCC patients, 36 patients (1.79% of the sample) had multiple BCCs, and three cases were diagnosed with basal cell nevus syndrome (BCNS). A total of 103 BCC lesions were confirmed in these patients, and each patient had 2 to 10 BCC lesions (Table 3).

Table 3.

Patients affected by multiple BCCs

No. of BCC lesions	Cases (%)
2	23 (63.89%)
3	6 (16.67%)
4	4 (11.11%)
6	1 (2.78%)
7	1 (2.78%)
10	1 (2.78%)

The detailed anatomical distribution of multiple tumors is presented in Table 4

The clinical characteristics of patients with multiple BCCs, categorized by the number of tumors, are outlined in Table 4 and contrasted with those of patients with a solitary BCC. Among individuals with a single BCC, males constituted 868 cases (868/1979, 43.86%), whereas females accounted for 1111 cases (1111/1979, 56.14%). In the group with multiple BCCs, 13 patients (13/36, 36.11%) were male, and 23 patients (23/36, 63.89%) were female; however, this difference was not statistically significant (P > 0.05). The mean age at initial diagnosis was 66.68 ± 12.06 years in patients with multiple BCCs, compared with 63.32 ± 13.48 years in those with a single BCC. For single BCCs, 31.40% (639/2035) of lesions occurred on the nose/perinasal region and 21.13% (430/2035) on the cheeks, whereas in patients with multiple BCCs, 26.21% (27/103) and 16.50% (17/103) of lesions affected these sites, respectively. In contrast, certain regions, including the mandible/chin and lips, showed very low or zero incidences of multiple lesions, indicating that these anatomical sites tend to harbor isolated tumors. Anatomic site distribution differed significantly between groups (P < 0.001) (Table 4).

Table 4.

Clinical characteristics of patients with single or multiple BCCs

	Single BCC	Multiple BCCs	χ2/t value	P
No. of pts	1979	36
Age*	63.32 ± 13.48	66.68 ± 12.06	2.257	0.133
Gender			1.124	0.289
Male	868 (43.86%)	13 (36.11%)
Female	1111 (56.14%)	23 (63.89%)
Anatomical site	2035	103	44.014	0.000
Head	1817 (89.29%)	77 (74.76%)
Scalp	97 (4.77%)	12 (11.65%)
Frontal/temporal	182 (8.94%)	7 (6.80%)
Periocular/eyebrow	285 (14.00%)	10 (9.71%)
Cheek	430 (21.13%)	17 (16.50%)
Nose/perinasal	639 (31.40%)	27 (26.21%)
Lips	79 (3.88%)	1 (0.97%)
Lower jaw/chin	47 (2.31%)	0 (0.00%)
Ear	58 (2.85%)	3 (2.91%)
Neck	18 (0.88%)	2 (1.94%)
Back	26 (1.28%)	2 (1.94%)
Chest/abdomen	78 (3.83%)	10 (9.71%)
Genital organ	33 (1.62%)	6 (5.83%)
Legs	54 (2.65%)	3 (2.91%)
Arms	9 (0.44%)	3 (2.91%)

^*At first diagnosis of BCC. BCC basal cell carcinoma, pts patients. In patients with multiple BCCs, most tumors were located on sun-exposed sites of the head and neck (particularly the nose, cheeks and periorbital region), with relatively fewer lesions on the trunk and extremities

Treatments and follow-up

Of the 2016 BCC patients, 97.82% (1972/2016) underwent surgical resection, including Mohs micrographic surgery (MMS), which was performed on 25 patients (25/2016, 1.24%). 15.13% (305/2016) of patients also received postoperative adjuvant therapies, such as superficial X-ray radiation or photodynamic therapy. For the 14 patients with extensive lesions and multiple BCCs, Sonidegib was administered either as a standalone treatment or in combination with photodynamic therapy, superficial X-ray radiation, or surgery. Following treatment, 1388 patients were monitored for a period of 5 years. However, 315 patients were lost to follow-up, and among the remaining 1073 patients, 44 experienced recurrence. The 5-year recurrence rate was 4.10% (44/1073). The recurrent cases were predominantly located in the exposed areas of the head and face, particularly the nose/perinasal area, followed by the periorbital area and ear. The average age of patients with recurrence was 62 years. Kaplan–Meier curves for RFS are shown in Fig. 4. Overall, RFS remained high in the evaluable cohort (Fig. 4A). When stratified by tumor lesion count, patients with multiple lesions exhibited significantly worse RFS compared with those with a single lesion (log-rank P < 0.0001, Fig. 4B). In the available medical records, no regional nodal or distant metastases were documented, and no BCC-related deaths were recorded during follow-up.

Fig. 4.

Kaplan–Meier curves for recurrence-free survival (RFS) in patients with BCC. A Kaplan–Meier estimate of RFS for the overall evaluable cohort (n = 1073). Time is shown in months. Tick marks indicate censored observations, and the number of patients at risk at each timepoint is provided below the plot. B Kaplan–Meier estimate of RFS stratified by tumor lesion count (multiple vs. single; multiple n = 19, Single n = 1054). Shaded areas indicate 95% confidence intervals. Group differences were assessed using the log-rank test (P < 0.0001). Tick marks indicate censored observations, and the number of patients at risk is shown below

Discussion

BCC is the most common NMSC worldwide and shows several distinctive clinicopathological patterns [1]. In our retrospective series of 2016 patients with 2138 BCC lesions from Southwest China, we extend current epidemiological data on BCC in Asian populations and provide region-specific evidence that can be compared with reports from Europe, North America and other parts of the world.

Consistent with prior studies, BCC predominantly affected older adults (average age > 60 years) and is rare in younger individuals (under 35 years) [10, 11]. In our cohort, incidence increased with age in individuals from the fifth decade to the eighth decade, and only 70 patients (3.50%) were younger than 35 years, with a modest female predominance. Studies suggest that early onset BCCs have distinct risk factors and clinicopathologic features in Asian populations, which may be associated with genetic predispositions or environmental exposures [12, 13]. The concordance between clinical impression and pathological diagnosis may be only moderate [14]. These observations underscore the need to rely on histopathological confirmation when evaluating young patients.

BCC typically arises on sun-exposed skin, particularly the faces. In this study, 80.64% of lesions were located on the faces, with a midface predilection: nose/perinasal region (31.15%), cheeks (20.91%), and periocular/eyebrow region (13.80%). Upper-limb involvement was rare (0.56%). This distribution mirrors prior reports that more than 80% of BCCs occur on the head/face/neck, likely reflecting cumulative UV exposure [15]. The nose and other facial H-area subsites (e.g., the ears and eyelids) are common and may carry higher recurrence risk [16], and BCCs at unusual sites (e.g., limbs or perianal region) remain rare [17]. The predominance of rural residents in our cohort may also reflect greater lifetime UV exposure from outdoor work and less consistent photoprotection. Overall, the facial predilection reinforces the role of UV damage in BCC pathogenesis [18]. Given functional and cosmetic constraints in high-risk facial zones, site-specific risk assessment remains important for surgical planning and follow-up [19].

Histopathological subtyping is clinically meaningful for risk stratification and management. Nodular BCC was the predominant subtype (71.94%) in our cohort, followed by infiltrative, adenoid, micronodular and superficial patterns, broadly consistent with prior series but with geographic variability [20, 21]. Nodular BCCs constitute 41.46% of low-risk BCCs and exhibit higher CK15 expression levels than infiltrative BCCs do [22]. Superficial BCC tumors are confined primarily to the epidermis or superficial dermis and exhibit multifocal growth patterns. Characteristic dermoscopic features aid in early diagnosis, including lobulated areas, radial distribution, and fine capillary dilation, often accompanied by multiple small erosions and milky-red plaques [23]. Ultrasound imaging has revealed distinct differences between superficial and nonsuperficial BCCs in terms of clear margins, regular morphology, and hypoechoic characteristics [24]. Morpheaform (sclerosing) BCC shows thin cord-like infiltration and poorly defined borders and is considered a high-risk subtype by the WHO [25]. Basosquamous BCCs account for 24.39% of high-risk BCCs and exhibit bidirectional basal and squamous differentiation. This subtype results in wider tumor–stroma separation clefts and COL10A1 overexpression in the stroma, indicative of enhanced stromal remodeling capacity, greater invasiveness, and poorer prognosis [26]. Overall, low-risk subtypes (e.g., nodular, superficial, and fibroepithelial) generally have lower recurrence, whereas high-risk subtypes (e.g., morpheaform, basosquamous, infiltrative, and micronodular) are more aggressive and show higher recurrence rates and occasional perineural involvement. Ki-67 and p53 are often elevated in high-risk subtypes, indicating enhanced proliferative activity [27]. The concordance between clinical diagnosis and histological subtyping is approximately 72%, necessitating adjunctive tools, such as dermatoscopy, to improve diagnostic accuracy [28, 29].

Clinically, nodular/ulcerative lesions were the leading presentation, followed by superficial (multiple) type, infiltrative and sclerotic type, and pigmented type, in that order. The presenting morphology of BCC provides prognostic clues for local behavior and recurrence risk. Nodular tumors are typically well-circumscribed and more amenable to complete excision, whereas ulceration and overt tissue destruction often indicate longer-standing growth and a higher likelihood of deeper invasion [27]. Infiltrative and morpheaform (sclerosing) BCCs characteristically show ill-defined, scar-like margins, which can delay diagnosis and increase the risk of positive margins and subsequent local recurrence [30]. Superficial (multiple) lesions are usually less deeply invasive but may extend laterally and present with field change, predisposing to incomplete clearance if margins are underestimated. This highlights the importance of integrating clinical appearance into risk stratification and treatment planning.

Multiple BCCs were uncommon in our series (1.79%), and three of these patients had BCNS. Because a substantial proportion of patients may develop additional primary lesions over time, individuals with multiple tumors merit closer longitudinal surveillance [31]. BCNS is a rare Hedgehog-pathway disorder characterized by early onset and multiple BCCs with systemic manifestations, and is most often associated with pathogenic variants in PTCH1 or SUFU [32–34]. Notably, syndromic BCC in Asian cohorts may present at a later age than reported in Western populations [35]. Beyond syndromic disease, additional inherited susceptibility and prior radiotherapy may contribute to multifocal disease and can be associated with more aggressive post-radiotherapy BCCs [36, 37].

Surgical excision remains the primary treatment modality for BCC. MMS is preferred for high-risk tumors (e.g., facial location, recurrent disease, or aggressive subtypes), because it provides real-time margin control and reduces recurrence [38]. Adjuvant approaches (radiotherapy, targeted therapy) are typically reserved for advanced or anatomically challenging tumors [39]. Our overall recurrence rate (4.10%) was lower than the 5–15% reported after conventional excision but higher than typical MMS outcomes (~ 3.80% at 5 years) [38], which may partly reflect underutilization of MMS in our cohort. Our time-to-event analysis further suggested heterogeneity in recurrence risk: Kaplan–Meier curves showed significantly shorter RFS in patients with multiple lesions than in those with a single lesion. Clinically, this finding suggests that patients with multiple tumors represent a higher risk subgroup requiring closer surveillance [40]. Given the small, unadjusted multiple-lesion subgroup, this signal should be interpreted cautiously and validated in larger cohorts with multivariable modeling. Recurrences, though rare, tended to involve high-risk facial areas, supporting risk-adapted margin selection, consideration of MMS when available, and structured long-term surveillance [41–43].

Despite the strengths of the large sample size and long observation period, this study has several limitations [44]. First, its retrospective, hospital-based design is subject to selection bias. Patients treated exclusively in primary care or oncology settings were not captured, which may limit generalizability beyond tertiary dermatology centers. Second, some clinically relevant variables, such as tumor size, symptom duration, Fitzpatrick phototype, cumulative UV exposure, family history and results of genetic testing, were incompletely documented and, therefore, could not be analyzed systematically. Third, slide review was not centralized across the three hospitals. Instead, original slides were re-reviewed only by dermatopathology specialists within each hospital, without a unified cross-institutional systematic re-review, which may have introduced inter-observer variability in subtype classification. Finally, although we report 5-year recurrence rates and provide Kaplan–Meier curves for recurrence-free survival, more comprehensive survival modeling (e.g., multivariable Cox regression) was beyond the scope of this descriptive analysis. These limitations should be considered when extrapolating our findings to other populations.

Conclusions

Taken together, this large cohort study of BCC patients from Southwest China provides region-specific evidence on susceptible populations, anatomic distribution, clinicopathological patterns, and recurrence. These findings may support risk-aware recognition, surgical decision-making in sensitive facial zones, and follow-up strategies.

Abbreviations

BCC

Basal cell carcinoma

BCNS

Basal cell nevus syndrome

NMSC

Non-melanoma skin cancer

RFS

Recurrence-free survival

MMS

Mohs micrographic surgery

UV

Ultraviolet

H&E

Hematoxylin and eosin

Author contributions

ZZ, JH, and XC conceptualized the manuscript. LZ, HG,JD, HZ, HH, and RZ conducted data collection and analysis. XC and JH drafted the initial version. ZZ, XY, and ZS provided detailed reviews and specific feedback on the draft. ZZ and XC revised the manuscript.

Funding

This work was supported by the National Natural Science Foundation of China (No. 82202035 to JH), the China Postdoctoral Science Foundation (No. 2023M734258 to JH), and the Natural Science Foundation of Chongqing, China (No. CSTB2022NSCQ–MSX0210 to JH).

Data availability

The datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request.

Declarations

Ethics approval and consent to participate

This retrospective study was conducted in accordance with the Declaration of Helsinki and was approved by the Ethics Committee of the First Affiliated Hospital (Southwest Hospital) of Army Medical University No. (B) KY2025151. Because only anonymized data extracted from existing medical records and the histopathological diagnosis system were used and no direct contact with patients occurred, the Ethics Committee waived the requirement for obtaining written informed consent to participate.

Consent for publication

Clinical photographs from seven patients are included in this article. Written informed consent for publication of their clinical details and accompanying images was obtained from all seven individuals. No other identifying personal data are presented.

Competing interests

The authors declare no competing interests.