Cutaneous basal cell carcinomas: distinct host factors are associated with the development of tumors on the trunk and on the head and neck

European consensus-based interdisciplinary guideline for diagnosis and treatment of basal cell carcinoma-update 2023

Basal cell carcinoma (BCC) is the most common malignant tumour in white populations. Multidisciplinary experts from European Association of Dermato-Oncology (EADO), European Dermatology Forum, European Society for Radiotherapy and Oncology (ESTRO), Union Européenne des Médecins Spécialistes, and the European Academy of Dermatology and Venereology developed updated recommendations on diagnosis and treatment of BCC. BCCs were categorised into 'easy-to-treat' (common) and 'difficult-to-treat' according to the new EADO clinical classification. Diagnosis is based on clinico-dermatoscopic features, although histopathological confirmation is mandatory in equivocal lesions. The first-line treatment of BCC is complete surgery. Micrographically controlled surgery shall be offered in high-risk and recurrent BCC, and BCC located on critical anatomical sites. Topical therapies and destructive approaches can be considered in patients with low-risk superficial BCC. Photodynamic therapy is an effective treatment for superficial and low-risk nodular BCCs. Management of 'difficult-to-treat' BCCs should be discussed by a multidisciplinary tumour board. Hedgehog inhibitors (HHIs), vismodegib or sonidegib, should be offered to patients with locally advanced and metastatic BCC. Immunotherapy with anti-PD1 antibodies (cemiplimab) is a second-line treatment in patients with a progression of disease, contraindication, or intolerance to HHI therapy. Radiotherapy represents a valid alternative in patients who are not candidates for or decline surgery, especially elderly patients. Electrochemotherapy may be offered when surgery or radiotherapy is contraindicated. In Gorlin patients, regular skin examinations are required to diagnose and treat BCCs at an early stage. Long-term follow-up is recommended in patients with high-risk BCC, multiple BCCs, and Gorlin syndrome.

Micronodular basal cell carcinoma of the scrotum: a case report and review of the literature

Introduction

Basal cell carcinoma is the most common nonmelanotic skin cancer. It has variable clinical and histological subtypes that vary in their aggressiveness and liability to recurrence and metastasis. Chronic ultraviolet radiation exposure is considered to be the main risk factor for developing basal cell carcinoma; therefore, it typically arises on sun-exposed skin, mainly the head and neck.

Case presentation

We present the case of a 55-year-old Caucasian male who presented with a lesion on the scrotum for 2 years. The lesion was clinically presumed benign and initially treated with curettage. Microscopic examination revealed an incompletely resected micronodular basal cell carcinoma with sebaceous differentiation. Therefore, a second excisional biopsy was performed to completely excise the incidentally discovered malignant tumor.

Conclusion

We report the first case of micronodular basal cell carcinoma arising on the scrotum. The goal of our article is to draw clinicians’ attention to the possible involvement of unexposed skin with basal cell carcinoma, and we highlight the importance of accurate diagnosis and prompt treatment due to the aggressive nature of micronodular basal cell carcinoma.

Review of the Molecular Genetics of Basal Cell Carcinoma; Inherited Susceptibility, Somatic Mutations, and Targeted Therapeutics

Simple Summary

Basal cell carcinoma is the most common human cancer worldwide. The molecular basis of BCC involves an interplay of inherited genetic susceptibility and somatic mutations, commonly induced by exposure to UV radiation. In this review, we outline the currently known germline and somatic mutations implicated in the pathogenesis of BCC with particular attention paid toward affected molecular pathways. We also discuss polymorphisms and associated phenotypic traits in addition to active areas of BCC research. We finally provide a brief overview of existing non-surgical treatments and emerging targeted therapeutics for BCC such as Hedgehog pathway inhibitors, immune modulators, and histone deacetylase inhibitors.

Abstract

Basal cell carcinoma (BCC) is a significant public health concern, with more than 3 million cases occurring each year in the United States, and with an increasing incidence. The molecular basis of BCC is complex, involving an interplay of inherited genetic susceptibility, including single nucleotide polymorphisms and genetic syndromes, and sporadic somatic mutations, often induced by carcinogenic exposure to UV radiation. This review outlines the currently known germline and somatic mutations implicated in the pathogenesis of BCC, including the key molecular pathways affected by these mutations, which drive oncogenesis. With advances in next generation sequencing and our understanding of the molecular genetics of BCC, established and emerging targeted therapeutics are offering new avenues for the non-surgical treatment of BCC. These agents, including Hedgehog pathway inhibitors, immune modulators, and histone deacetylase inhibitors, will also be discussed.

Development of Multiple-Lesion Basal Cell Carcinoma of the Skin: A Comprehensive Review

An interesting clinical feature of basal cell carcinoma (BCC) of the skin is a marked variation in tumor number, sites, and accrual. Some individuals develop only a single BCC lesion with no impact on health status, while a significant proportion is affected repeatedly with new primary tumors at various body sites. Approximately 29% of patients with a first BCC will develop at least 1 more lesion during their lifetime. The candidate predictors for multiple BCC development include younger age and a superficial BCC subtype at the time of the first diagnosis, red hair phenotype, initial or frequent tumor location on the trunk or on the upper limbs, and male gender. The pathogenesis of multiple BCC development does not seem to be related to greater UVR exposure. Individual genetic susceptibility may have a greater impact than extrinsic factors. In clinical practice, it is meaningful to estimate the probability of new BCC development in patients who have an initial lesion. A reliable prediction model for individualized risk stratification remains a subject of continued research; however, a focus on the risk factor profile is beneficial for clinical screening and may help clinicians to determine the individuals who should be followed up more closely.

Diagnosis and Treatment of Basal Cell Carcinoma in Specialized Dermatology Units: A Clinical Practice Guideline

BACKGROUND AND OBJECTIVE

Basal cell carcinoma (BCC) is the most common skin cancer in the general population. BCC is managed in a variety of ways, and available international guidelines are difficult to put into practice in Spain. This guideline aims to improve the management of BCC based on current evidence and provide a point of reference for Spanish dermatologists.

MATERIAL AND METHODS

Members of the Spanish Oncologic Dermatology and Surgery Group (GEDOC) with experience treating BCC were invited to participate in drafting this guideline. The drafters used the ADAPTE collaboration process to develop the new guideline based on existing ones, first summarizing the care pathway and posing relevant clinical questions. They then searched for guidelines, assessed them with the AGREEII (Appraisal of Guidelines for Research and Evaluation) tool, and searched the selected guidelines for answers to the clinical questions. Finally, the recommendations were drafted and submitted for external review.

RESULTS

The highest-scoring guidelines were from the Association of Dermatologists, the National Comprehensive Cancer Network, the European Dermatology Forum, and the European Academy of Dermatology and Venereology. A total of 11 clinical questions were answered.

CONCLUSIONS

This new guideline answers the working group's clinical questions about the routine management of BCC in Spain. It provides dermatologists with a tool they can use for decision-making while taking into consideration the resources available and patient preferences.

Periocular basal cell carcinoma - clinical perspectives

Basal cell carcinoma (BCC) as a non-melanoma skin cancer type is the most common malignant tumor throughout the world. The incidence is higher in age over 60. The intense of exposure to ultraviolet radiation is one of the known risk factors. Over 50% of BCC of the periocular region initially occur on the lower lid and inner angle. Literature review of treatment options for basal cell carcinoma, which consist of surgery, or combined techniques plus vismodegib, radiotherapy and imiquimod. The first consideration for treatment of periocular BCC is radical surgical excision using Mohs micrographic technique. Functional and esthetic outcome in patients are important after clear excisions and reconstruction should be carefully considered. Radical exenteration is considered in the case of orbital invasion of high-risk aggressive BCC.

Eruptive Basaliomas: "Why we have to Perform Surgery?" Or Said Otherwise: "Catch The Metatypical!"

BACKGROUND

Keratinocyte cancers are malignant diseases with a broad incidence of spread which tends to increase during the last couple of decades. The solar radiation plays a dominant role in the occurrence of BCC, but certain genetic phenotypes appear to be risky from an etiological point of view. Metatypical basal cell carcinoma (MTBCC) is a rare variant of BCC which combines the clinical and histological characteristics of BCC and SCC. Clinically they are indistinguishable from the conventional BCC, and only the histological examination can differentiate them. The MTBCC is a histological subtype which is considered more aggressive due to its ability to produce local recurrences or distant metastases.

CASE REPORT

We present a 44-year old patient with multiple BCCs disseminated on the face and body. The biopsy established mixed type histology: three metatypical and four solid BCCs. The lesions were removed via elliptical excision with a field of operational security of 0.5 cm in all directions.

CONCLUSIONS

The eruptive (multiple) BCCs are a challenge about the choice of a therapy option. This is because clinically completely identical tumours show different histopathological characteristics, namely those with a tendency to metastasise. Having in mind one of the hypotheses of metatypical BCC emergence - the improper or inadequate radiotherapy (as a choice of therapy) could trigger the transition of a conventional tumour to a metastasising one, the surgical treatment appears to be the most secure treatment method.

Characteristics of multiple basal cell carcinomas: The first study on Japanese patients

Basal cell carcinoma (BCC), the most frequent skin cancer, has been increasing in incidence. However, the characteristics of multiple BCC have not been clarified in Japan. Therefore, we conducted a retrospective study to elucidate the features of multiple BCC compared with solitary BCC. The study population consisted of 327 patients with histopathologically proven BCC who were referred to the Department of Dermatology in Tottori University Hospital between November 2006 and April 2016. Of the 327 patients, 304 (93.0%) had solitary BCC and 23 (7.0%) had multiple BCC. The mean age of the patients with solitary BCC was 74.7 years (range, 31-102) and that of patients with multiple BCC was 79.3 years (range, 63-91). There was a significant difference in mean age between the two groups (P = 0.01). Approximately four-fifths of the BCC were located on the head or neck in the total study population. In the group of patients with multiple BCC, the incidence of lesions on the head and neck was lower and that on the trunk was higher than those in patients with solitary BCC. There was a significant difference in the tumor site between the two groups (P < 0.0001). With respect to tumor histopathology, the ratio of superficial BCC was significantly higher in the group of patients with multiple BCC than in the group of patients with solitary BCC (P < 0.0001). In conclusion, we demonstrated that older age, truncal location and superficial histopathological type of tumor are features of multiple BCC in Japanese subjects.

Updates on the Management of Non-Melanoma Skin Cancer (NMSC)

Non-melanoma skin cancers (NMSCs) are the most common malignancy worldwide, of which 99% are basal cell carcinomas (BCCs) and squamous cell carcinomas (SCCs) of skin. NMSCs are generally considered a curable diseases, yet they currently pose an increasing global healthcare problem due to rising incidence. This has led to a shift in emphasis on prevention of NMSCs with development of various skin cancer prevention programs worldwide. This article aims to summarize the most recent changes and advances made in NMSC management with a focus on prevention, screening, diagnosis, and staging.

Occurrence of metachronous basal cell carcinomas: a prognostic model

BACKGROUND

A third of patients with a first basal cell carcinoma (BCC) will develop subsequent (metachronous) BCCs.

OBJECTIVES

To study the prognostic effect of the number of previous BCC diagnosis dates a patient has experienced to derive a prediction model to assess the risk of metachronous BCCs that may inform individualized decision making on surveillance.

METHODS

We considered participants of north-western European ancestry from a prospective population-based cohort study (Rotterdam Study). After linkage with the Dutch Pathology Registry, 1077 patients with a first BCC were included. Candidate predictors for metachronous BCCs included patient, lifestyle and tumour characteristics. The prognostic model was developed with Fine and Gray regression analysis to account for competing risk of death. We used bootstrapping to correct for within-patient correlation and statistical optimism in predictive performance.

RESULTS

Second to fifth BCCs occurred in 293, 122, 58 and 36 patients, with median follow-up times of 3·0, 2·1, 1·7 and 1·8 years after the previous BCC, respectively. The risk of a new BCC was higher for patients with more metachronous BCCs. Having more than one BCC at diagnosis was another strong predictor of metachronous BCCs. Discriminative ability of the model was reasonable with an optimism-corrected c-index of 0·70 at 3 years.

CONCLUSIONS

The number of previous BCC diagnosis dates was a strong prognostic factor and should be considered when predicting the risk of metachronous BCCs. When the number of previous BCC diagnosis dates is combined with other readily available characteristics into a prognostic model, patients at high risk of a new BCC can be identified.

Basal cell carcinomas on sun-protected vs. sun-exposed body sites: a comparison of phenotypic and environmental risk factors

BACKGROUND

Basal cell carcinoma (BCC) is the most commonly diagnosed cancer in White populations. There are indications that risk factors for BCC may differ according to the anatomic site of the tumour but this is not well understood.

PURPOSE

To compare phenotypic and environmental risk factors for BCCs arising on sun-protected sites with that of those on sun-exposed sites.

METHODS

We conducted a case-case study in which people who had been diagnosed with incident BCC were recruited between February 2012 and September 2013 in Brisbane, Australia.

RESULTS

Fair skin (OR: 4.50; 95% CI: 1.22, 16.59), having more than 15 lesions frozen/burnt off compared to less than 5 (OR: 5.68; 95% CI: 1.78, 18.08) and severe acne (OR: 5.25; 95% CI: 1.34, 20.56) were associated with increased risk of BCC on sun-protected sites. The presence of more than 5 nevi on the body was associated with decreased risk (OR: 0.28; 95% CI: 0.11, 0.71).

CONCLUSIONS

BCCs on sun-protected sites arise as a result of excessive sun exposure, most likely combined with phenotypic susceptibility. The strong negative association with nevi also suggests that there are constitutional factors that underlie the propensity for BCCs to arise on these body sites.

Basal cell carcinoma in Singapore: a prospective study on epidemiology and clinicopathological characteristics with a secondary comparative analysis between Singaporean Chinese and Caucasian patients

BACKGROUND/OBJECTIVES

Susceptibility to and clinical presentation of basal cell carcinoma (BCC) differ in Asian and Caucasian populations. This study aims to evaluate the epidemiological and clinicopathological characteristics of BCC in a multiracial Singaporean population, with a secondary comparative analysis between Chinese and Caucasian patients.

METHODS

We prospectively studied patients with newly diagnosed, histologically confirmed BCC at the National Skin Centre, Singapore from 2004 to 2008.

RESULTS

In total, 274 BCC from 260 patients were studied, with 19 patients having two or more tumours. Their mean age was 67.5 years and 54% were male. Chinese comprised 80% and Caucasians 14%. The Chinese were 1.8-fold as likely as Caucasians to be older than 60 years, and experienced itch thrice more frequently. Caucasians developed multiple BCC threefold and truncal or upper limb BCC 2.9-fold more frequently than the Chinese. In terms of tumour subtype, morphoeic BCC was 2.7-fold more common in Caucasians. Pigmented BCC occurred 2.7-fold more often in the Chinese, most frequently on the head and neck of elderly Chinese.

CONCLUSIONS

Compared to the Chinese, BCC occurred more often in younger Caucasians, with a predilection for the trunk and upper limb, suggesting a greater role for recreational sun exposure as a risk factor. Pigmented BCC more commonly occurred on the head and neck of elderly Chinese and may be reflective of cumulative sun exposure as a risk factor. Aggressive morphoeic BCC was more common in Caucasians than in Singaporean Chinese patients.

Comparison of risk factors of single Basal cell carcinoma with multiple Basal cell carcinomas

Background:

Basal cell carcinoma (BCC) is the most common malignant skin tumor. Although mortality attributable to BCC is not high, the disease is responsible for considerable morbidity. There is evidence that the number of patients who develop more than one BCC is increasing.

Aims:

The aim of this study was to elucidate possible risk factors for developing Multiple BCC.

Patients and Methods:

Patients with histologically proven BCC (n = 218) were divided into two groups (single BCC and Multiple BCC) according to the number of their tumors and their profile were reviewed. Probable risk factors were compared between these two groups.

Results:

Among 33 evaluated risk factors, mountainous area of birth, past history of BCC, history of radiotherapy (in childhood due to tinea capitis), abnormal underlying skin at the site of tumor, and pigmented pathologic type showed significant differences between the two groups.

Conclusions:

The high rate of additional occurrences of skin cancers among patients with previously diagnosed BCC emphasizes the need of continued follow-up of these individuals. Those with higher risk require closest screening.

Anatomic location of Basal cell carcinomas may favor certain histologic subtypes

BACKGROUND

Differences in age, site, and subtype exist in basal cell carcinoma (BCC).

OBJECTIVE

To evaluate whether an independent association exists between the anatomic location and the histologic subtype of BCC.

MATERIALS AND METHODS

A series of 3,254 BCCs was examined. The location was the head/neck (n  =  1,766), limbs (n  =  362), trunk (n  =  1,113), or genitals (n  =  13). Subtype was classified as superficial, nodular, micronodular, morpheic-infiltrative, or fibroepithelial.

RESULTS

Prevalence of BCCs on the head/neck or chest/abdomen increased with age (p < .001). The prevalence of superficial subtype decreased with age (p < .0001), whereas the prevalence on nodular subtype increased (p < .0001). Subtype was associated with location (p < .0001). The prevalence of superficial subtype was lower among BCCs on the head/neck than other locations (24.9% vs 64.4%, OR 0.18, 95% CI 0.16-0.21). The prevalence of nodular or morpheic/infiltrative subtype was higher among BCCs on the head/neck than other locations, that is, 57.1% versus 29.2%, OR 3.23, 95% CI 2.79 to 3.74 (nodular) and 16.1% versus 4.0%, OR 4.56, 95% CI 3.42 to 6.08 (morpheic/infiltrative).

CONCLUSION

Anatomic location and subtype of BCC were associated with age, but the anatomic location was the only independent predictor of histologic subtype. Although a bias by referral patterns may not be excluded, the results suggest that the anatomic location may favor the development of particular BCC subtypes.

Changing pathology with changing drugs: skin cancer

Today skin cancer is mainly treated by surgical interventions. New findings concerning molecular biology and the signaling pathways in epithelial skin cancers such as basal cell carcinoma, squamous cell carcinoma or melanoma, and mesenchymal skin cancers such as angiosarcoma and dermatofibrosarcoma protuberans (DFSP) have identified new molecular targets for a systemic or local treatment approach. For DFSP there is an opportunity already today to reduce the intensity of surgical procedures by pretreatment with targeted therapy. This article highlights important aspects in several skin cancer types.

Could Malassezia yeasts be implicated in skin carcinogenesis through the production of aryl-hydrocarbon receptor ligands?

Malassezia yeasts are found on the skin of all humans and many warm-blooded animals. In vitro they have the ability to synthesize potent ligands (indolo[3,2-b]carbazole, malassezin and indirubin) of the aryl-hydrocarbon receptor (AhR; synonym: dioxin receptor) when the sweat contained L-tryptophan is used as the single nitrogen source. The production of these AhR-ligands has been associated with pathogenic strains of a certain Malassezia species (Malassezia furfur) but recent evidence shows that this property is widely distributed in almost all currently known Malassezia species. AhR is associated with carcinogenesis and the potential connection of these ubiquitous skin symbionts, and putative pathogens, with skin neoplasia should be evaluated mainly focusing on mechanisms related to the distinctive ability of the yeast to produce potent AhR ligands.

HYPOTHESIS

Synthesis of available pertinent data show a possible link between Malassezia produced AhR ligands and skin carcinogenesis, particularly of basal cell carcinoma (BCC). BCCs are almost exclusively observed in animal species colonized by Malassezia. In humans and animals there is overlapping in the skin regions colonized by this yeast and affected by BCC. The potent AhR ligands synthesized by pathogenic Malassezia strains could contribute to tumor promotion by: modification of the UV radiation carcinogenesis, alterations in the salvage/survival of initiated tumor cells, inhibition of cell senescence, interaction with vitamin D metabolism, promotion of immune tolerance and finally pro-carcinogenic modulation of cell cycle progression and apoptosis.

Basal cell carcinoma: what's new under the sun

Basal cell carcinoma (BCC) is the most common skin cancer in white populations with an increasing incidence worldwide, thereby imposing an important public health problem. Its etiology is still unclear, but existing data indicate that the risk for BCC development is of multifactorial origin and results from the interplay of both constitutional and environmental factors. Yet, UV radiation (UVR) is believed to be the predominant causative risk factor in the pathogenesis of BCC. For years, BCC and squamous cell carcinoma (SCC) have been grouped together as "nonmelanoma skin cancer." However, it seems that there are considerable biologic differences between BCC and SCC, and thus each type of epithelial cancer should be addressed separately. The present review provides an overview of the intriguing etiologic link of BCC with UVR and attempts a comprehensive review of recent epidemiologic and molecular evidence that supports this association.

Non-melanoma skin cancer

The rising incidence and morbidity of non-melanoma skin cancers has generated great interest in unravelling of their pathogenesis and in the search for new non-invasive treatments. Whereas the role of cumulative sun exposure in pathogenesis of squamous-cell carcinoma seems clear, the relation between sun-exposure patterns and subtypes of basal-cell carcinoma remains undetermined. Several complex genotypic, phenotypic, and environmental factors contribute to pathogenesis of non-melanoma skin cancers. Unlike basal-cell carcinoma, squamous-cell carcinomas can arise from precursor lesions. Diagnosis of non-melanoma skin cancer is made clinically and confirmed by histological testing. Prognosis depends on lesion and host characteristics, which also dictate choice of treatment. Prevention strategies aim at reduction of sun exposure, but are of unproven benefit, especially for basal-cell carcinoma. Surgical excision with predetermined margins is the mainstay of treatment for squamous-cell carcinoma and for most basal-cell carcinomas. Of the new non-invasive treatments, only photodynamic therapy and topical imiquimod have become established treatments for specific subtypes of basal-cell carcinoma, and the search for more effective and tissue-salvaging therapies continues.

Guidelines for the management of basal cell carcinoma

This article represents a planned regular updating of the previous British Association of Dermatologists guidelines for the management of basal cell carcinoma. These guidelines present evidence-based guidance for treatment, with identification of the strength of evidence available at the time of preparation of the guidelines, and a brief overview of epidemiological aspects, diagnosis and investigation.

Risk Factors for Histological Types and Anatomic Sites of Cutaneous Basal-Cell Carcinoma: An Italian Case–Control Study

Different clinico-pathologic subtypes and anatomic sites of basal-cell carcinoma (BCC) may display distinct characteristics and mechanisms of development. However, scanty information exists on potential differences in etiological factors for BCC according to histotype and anatomic location. Thus, we analyzed data from an Italian case-control study, including 528 subjects with newly diagnosed, histologically confirmed BCC and 512 controls admitted to the same hospitals with acute conditions. The multivariate odds ratio (OR) of nodular (OR=1.53) but not superficial (OR=0.71) BCC was increased for occupational exposure to sunlight. Considering the anatomic site of BCC, the corresponding values were 1.46 for head/neck and 0.74 for truncal location. Direct associations were observed with recreational sunlight exposure, eye color, red hair, and number and early age of severe sunburn episodes, along with some differences in risk between histotypes and anatomic sites. This study confirmed the role of (intermittent) sun exposure and phenotypic characteristics as risk factors for BCC, and suggested etiological differences between nodular and superficial histotypes and between head/neck and truncal locations.

Basal cell carcinoma on the trunk is associated with excessive sun exposure

BACKGROUND AND OBJECTIVE

Basal cell carcinoma (BCC) is the most common of all cancers. Ultraviolet radiation is the major etiologic agent in the pathogenesis of BCC, but there is not a straightforward relationship between cumulative exposure and risk. A high proportion of lesions arise on the trunk, which is generally much less exposed to the sun than the head, the major site affected. We tested the hypothesis that the phenotypic determinants and patterns of sun exposure that give rise to BCC on the head and trunk vary in a way that explains the anomalous site distribution.

METHODS

The study was set in the context of the Nambour Skin Cancer Study, a community-based follow-up study among 1621 participants with virtually complete ascertainment of BCCs between 1992 and 2004. We compared phenotypic and sun exposure characteristics of participants who developed a first BCC of the head or trunk with those of participants who had no diagnosis of BCC.

RESULTS

BCCs of the trunk were more likely to occur in men; they also occurred at a younger age than BCCs of the head. There was a positive association between sun sensitivity and BCC of the head that was absent for BCC of the trunk. A high number of solar keratoses conferred a greater than 3-fold risk for BCCs of both the head and the trunk. BCCs of the trunk had a particularly strong association with the number of reported sunburns and solar lentigines on the trunk, whereas many lentigines conferred a greater than 3-fold risk of truncal BCC compared with a 50% increased risk of BCC of the head.

LIMITATIONS

The relatively small numbers of tumors may have limited our ability to detect statistically significant differences.

CONCLUSIONS

BCCs of the trunk are the result of overexposure of the sensitive basal cells of the epidermis to ultraviolet radiation. This may result from acute intense exposures sufficient to cause sunburn among people whose ability to tan makes the skin of their face generally less susceptible to the carcinogenic effects of ultraviolet radiation.

Polymorphism in the nuclear excision repair gene ERCC2/XPD: association between an exon 6-exon 10 haplotype and susceptibility to cutaneous basal cell carcinoma

Cutaneous basal cell carcinoma (BCC) risk is mediated by interactions between ultraviolet radiation (UVR) and host factors, including DNA repair efficiency. We investigated the association between BCC risk and SNPs in exon 6 (c.466C > A, dbSNP238406:g.C > A; designated C/A156), exon 10 (c.932G > A, dbSNP1799793:g.G > A; designated G/A312), and exon 23 (c.2251A > C, dbSNP13181:g.A > C; designated A/C751) of the nucleotide excision repair gene, XPD (ERCC2; excision repair cross-complementing repair deficiency, complementation 2 [xeroderma pigmentosum D]). XPD genotype frequencies were not significantly different in 509 cases and 379 controls, although AA156 (odds ratio [OR]=0.61, 95% confidence interval [CI]=0.37-1.01, P=0.052) and AA312 (OR=0.65, 95% CI=0.40-1.05, P=0.08) were linked with reduced risk. A156-A312 and A156-A312-A751 haplotype frequencies however, were significantly lower in cases than controls (OR=0.12, 95% CI=0.05-0.31, P < 0.001; OR=0.10, 95% CI=0.03-0.33, P < 0.001). We confirmed the robustness of these findings by showing significant associations of the haplotypes with risk in two randomly selected equal sized groups of cases and controls and, using the false positive report probability (FPRP) approach (FPRP values < 0.001 and < 0.004, respectively). A156-A312 was similarly associated with reduced risk in subgroups, including cases with no family history of skin cancer, with only BCC on the head/neck, and those with a high rate of increase in BCC numbers. The association was not dependent on gender, age, or extent of UVR exposure. A156-A312 was found in 6.3% of controls and the corresponding risk haplotype, C156-G312 (OR=1.65, 95% CI=1.21-2.26, P=0.002) in 35.4% of controls. We interpret these data as showing that XPD SNP mediate susceptibility to BCC.

Site-specific occurrence of nonmelanoma skin cancers in patients with cutaneous melanoma

In a registry-based case–control study, we compared the site-specific occurrence of nonmelanoma (keratinocytic) skin cancers among patients with cutaneous melanoma cases (cases, n=3774) and solid tumours (controls, n=349 923), respectively. Overall, patients with melanoma were almost five-fold more likely to develop keratinocytic cancers compared with solid tumour controls (adjusted OR 4.7, 95% CI 4.1–5.3), but the risks varied depending upon the site of melanoma. Whereas patients with melanoma of the head and neck had similarly increased risks of keratinocytic cancers across all body sites, patients with melanoma of the trunk were significantly more likely to develop keratinocyte cancer diagnosed on the trunk (adjusted OR 12.5, 95% CI 7.2–20.2) than on the head and neck (adjusted OR 3.0, 95% CI 2.2–4.3). Similar colocalisation of skin tumours was observed for patients with melanomas of the lower limb. These findings provide support for the hypothesis that skin cancers at different anatomical sites may arise through different causal pathways.

Susceptibility to basal cell carcinoma: associations with PTCH polymorphisms

Loss of function of the human patched gene (PTCH) is common and critical in basal cell carcinoma (BCC) development. Indirect evidence suggests polymorphism in PTCH mediates BCC risk. We studied 659 BCC cases and 300 controls to determine if exon 2(318), 3(429), 11(1552), 12(1665), 12(1686), 14(2199) and 23(3944) and intron 9(1336-135) and 15(2560+9)PTCH variants were sufficiently common for use in case-control studies, and if selected markers were associated with risk. Intron 15(2560+9) and exon 23(3944) variants were studied further. Their genotype frequencies were not significantly different in controls and cases, though frequency of the G(2560+9)-C(3944) haplotype was lower in all cases (odds ratio=0.44, p=0.009) and those stratified by BCC site and rate of development of further tumours. This association was not mediated by the extent of UVR exposure. We confirmed the robustness of these findings by showing these associations demonstrated similar odds ratios in two groups of randomly selected cases and controls, and using the false positive report probability (FPRP) approach described by Wacholder et al. (2004). The FPRP value (0.168) was in the noteworthy category. These data, showing for the first time that PTCH polymorphism mediates susceptibility, are compatible with reports showing that PTCH haploinsufficiency influences development of BCC precursor lesions.

Associations between ultraviolet radiation, basal cell carcinoma site and histology, host characteristics, and rate of development of further tumors

BACKGROUND

Patients with basal cell carcinoma (BCC) frequently develop further tumors during follow-up.

OBJECTIVE

We sought to elucidate the relative effects of pattern of ultraviolet radiation exposure, and site and histologic type of the first tumor, on the rate of increase in BCC numbers.

METHODS

We used negative binomial regression analysis to study the association of selected variables on the rate of increase in BCC numbers in 266 Caucasian patients who first presented with a tumor on the head/neck or trunk with nodular or superficial histology.

RESULTS

Patients with an initial truncal BCC with superficial histology demonstrated significantly faster increases in BCC numbers than did patients with other site and histology combinations.

CONCLUSIONS

These data indicate that site and histology define subsets of patients with BCC.

Basal cell carcinoma: from host response and polymorphic variants to tumour suppressor genes

The molecular factors and events that characterize susceptibility and outcome in cutaneous basal cell carcinoma (BCC) have been the focus of much research interest. As a result, we are beginning to understand the complex relationships between exposure to ultraviolet radiation (UVR), host response and the resulting damage to key genes that characterize these tumours. In this review, we will focus on genetic factors that influence susceptibility and outcome. While the search for susceptibility genes has generally resulted in the identification of low penetrance allelic variants, studies on modifier genes influencing outcome variables such as tumour number, age of onset and tumour subtype have identified factors with higher potential impact. Here we will briefly describe some recent work on the genetic basis of the immune response to UVR, the effect of UVR on the generation of reactive oxygen species and their detoxification, and the role of onco- and tumour suppressor genes. Areas for further research are highlighted, together with a consideration of possible applications in clinical practice.

Associations between UVR exposure and basal cell carcinoma site and histology

While sunlight is critical in basal cell carcinoma (BCC) pathogenesis the relationship between exposure and tumor site and histology is unclear. We determined if tumor site (trunk or head/neck) or histology (nodular or superficial) is determined by exposure pattern. In 66 cases with truncal and 362 patients with head/neck BCC at first presentation, average hours exposure/year, intermittency score, childhood sunburning and skin type were not significantly associated with tumor site or histology. However, often sunbathing was associated with a five-fold increased risk of truncal BCC. Average sunbathing score was significantly greater in 22 cases with truncal compared with 325 cases with head/neck nodular tumors and also in 44 cases with superficial truncal compared with superficial head/neck BCC. Thus, sunbathing determined tumor site but not histology.

Modulation of Patched-Associated Susceptibility to Radiation Induced Tumorigenesis by Genetic Background

We described previously a basal cell carcinoma (BCC) and medulloblastoma (MB) phenotype for CD1Ptch1(neo67/+) mice exposed to ionizing radiation. Ptch1 heterozygous mice mimic the predisposition to BCC and MB development of patients affected by nevoid BCC syndrome that inherit a mutant Patched (Ptch1) allele. To examine the impact of genetic background on development of BCCs and other tumors we used two outbred mouse lines characterized by extremely high, carcinogenesis-susceptible (Car-S), and low, carcinogenesis-resistant (Car-R), susceptibility to skin carcinogenesis. Crosses between Ptch1(neo67/+) mice and Car-S (F1S) or Car-R mice (F1R) were exposed to ionizing radiation. F1SPtch1(neo67/+) mice were highly susceptible to radiation-induced BCCs, whereas F1RPtch1(neo67/+) mice were completely resistant, indicating that tumor penetrance can be modulated by genetic background. Development of microscopic and macroscopic BCC lesions was influenced by Car-S and Car-R genotypes, suggesting a genetic-background effect on both initiation and progression of BCC. Susceptibility was additionally increased in N2 backcross mice (Car-S x F1SPtch1(neo67/+)), showing a contribution from recessive-acting Car-S modifiers. The modifying effects of Car-S-derived susceptibility alleles were tissue specific. In fact, despite higher susceptibility to BCC induction, Car-S-derived lines had lower MB incidence compared with CD1Ptch1(neo67/+) mice. BCC-associated somatic events were not influenced by genetic background, as shown by similar rate of wild-type Ptch1 loss in BCCs from F1SPtch1(neo67/+) (93%) and CD1Ptch1(neo67/+) mice (100%). Finally, microsatellite analysis of BCCs showed Ptch1 loss through interstitial deletion. These results are relevant to humans, in which BCC is the commonest malignancy, because this model system may be used to study genes modifying BCC development.

PTCH polymorphism is associated with the rate of increase in basal cell carcinoma numbers during follow-up: preliminary data on the influence of an exon 12-exon 23 haplotype

After first presentation with a basal cell carcinoma (BCC), patients demonstrate interindividual diversity in the rate of development of further BCCs (number/year of follow-up). The mechanism for this variation is unknown. In this study, we evaluated whether PTCH variants mediate this phenomenon. We used negative binomial regression analysis to identify associations between BCC numbers/year and host characteristics, parameters of exposure to ultraviolet radiation (UVR), and PTCH exon 12(1686) C/T, intron 15(2560+9) G/C, and exon 23(3944) C/T genotypes and haplotypes in 279 BCC cases who presented with an initial tumor on the head/neck. PTCH genotypes were not significantly associated with BCCs/year, although cases with two copies of the C1686-C3944 haplotype developed significantly fewer BCCs/year than those without this haplotype (rate ratio = 0.44; 95% CI = 0.27-0.71). Cases with one copy of T1686-T3944 developed more BCCs/year (rate ratio = 2.46; 95% CI = 1.27-3.97) than those without the haplotype. We found no significant associations between BCCs/year and the other PTCH haplotypes studied. We reexamined the association of C1686-C3944 with BCCs/year in a model that included UVR exposure parameters (sunburning in childhood, sunbathing score, intermittency of exposure between 40 and 60 years of age, exposure in hours/year) and skin type, gender, and age at first presentation. The association between C1686-C3944 and BCCs/year remained significant (rate ratio = 0.44; 95% CI = 0.26-0.73 for two copies of the haplotype). The data show that allelic variation in PTCH contributes to the rate of development of BCC.

Basal cell carcinoma

The authors of this review aim to provide a comprehensive overview of basal cell carcinoma, concentrating in particular on incidence, risk factors, molecular genetics, clinical features, and treatment

Combined effects of gender, skin type and polymorphic genes on clinical phenotype: use of rate of increase in numbers of basal cell carcinomas as a model system

Patients with a basal cell carcinomas (BCC) have an increased risk of further tumors. We studied the individual and combined impact of gender, skin type and allelic genes cytochrome P450 (CYP2D6), vitamin D receptor (VDR), tumor necrosis factor-alpha, TNF-alpha) on the rate of increase in BCC numbers after first presentation. Individually, male gender, skin type 1, CYP2D6 EM, VDR TT and TNF-alpha GG were associated with more BCC/year (rate ratio (RR) 1.20-1.36) while RR for associations of combinations of two, three and four variables were greater than in their reference categories (RR 1.32-1.90, 2.20-2.84, 3.06-5.49, respectively). The data show that different factors mediate the numbers of BCC/year in males and females and, the individual contributions of variables to risk is modest.

Environment, phenotype and genetics: risk factors associated with BCC of the skin

Basal cell carcinoma is the most common cancer in Caucasians and its incidence is rising. Whilst not life threatening, the tumor can cause substantial morbidity and because of long follow-up, it places a major burden on healthcare agencies worldwide. Patients with the disease demonstrate wide phenotypic diversity with respect to tumor numbers, rate of tumor appearance and site. The factors involved in patient susceptibility to basal cell carcinoma are not well understood although exposure to ultraviolet radiation in sunlight appears critical. In this review we discuss the role of environmental and genetic factors on predisposition to basal cell carcinoma and illustrate how stratification of the basal cell carcinoma cohort into high-risk subgroups is helpful in identifying factors significant in disease susceptibility.

Susceptibility and modifier genes in cutaneous basal cell carcinomas and their associations with clinical phenotype

While ultraviolet radiation (UV) is critical in the pathogenesis of basal cell carcinomas (BCC), its role in determining the phenotypic variation shown by patients is unknown. Thus, patients manifest variation in BCC numbers, patterns of presentation and tumour site. We have used this diversity to classify patients into subgroups that are associated with different risks of developing tumours. Two phenotypes are particularly interesting. Firstly, presentation with clusters of BCC. These patients, termed multiple presentation phenotype (MPP), had two to five BCC at one presentation, suggesting rapid accrual over short periods of time. They comprised 15% of our 1200 BCC patients. A minority of patients demonstrated multiple clustering events, a phenomenon that is associated with a genetic pre-disposition. The second risk phenotype, characterised by tumours on the trunk, is also associated with a pre-disposition. Both phenotypes were characterised by a susceptibility to develop numerous BCC. Thus, all our patients with more than five BCC had one or both of these phenotypes. We are using a candidate gene approach to identify loci associated with risk of these phenotypes (susceptibility genes) and tumour numbers in them (modifier genes). Interestingly, we did not identify differences in UV exposure between patients with high- and low-risk phenotypes.