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Successfully delivering medical care and acquiring and disseminating the new knowledge that underpins clinical advance requires dealing with a number of both theoretical and organizational issues that may impede progress. Firstly, we have to move beyond the idea that biology and medicine are synonymous, and realize that tropes such as 'bench to bedside' or 'translational' frequently do not capture the way medical advance occurs. Medicine is more engineering than science, and the constraints imposed by society and economics, as well as historical models of working, may all delay improvements in healthcare delivery. Secondly, the generation of new ideas is influenced by the social organization and financial underpinning of science. Comparisons with other areas of science and technology suggest that medical science is dysfunctional and lacking in genuine innovation, particularly when cost is factored in as a key denominator. There are reasons to believe that matters are getting worse, and that the climate for revolutionary discovery is less supportive in both academia and industry than it was in the mid-to-late twentieth century. Thirdly, healthcare delivery is subject to a number of factors that limit cheap and effective care. These include payment systems that encourage unnecessary care, self-interest by medical guilds and insurers, and regulators that seek to limit new ways of working. Finally, there is also a striking failure to study and understand medical competence, how we educate doctors and other clinicians, and how technology might help to reduce costs., (© 2015 British Association of Dermatologists.)

Using an experimental task in which lay persons were asked to distinguish between 30 images of melanomas and common mimics of melanoma, we compared various training strategies including the ABC(D) method, use of images of both melanomas and mimics of melanoma, and alternative methods of choosing training image exemplars. Based on a sample size of 976 persons, and an online experimental task, we show that all the positive training approaches increased diagnostic sensitivity when compared with no training, but only the simultaneous use of melanoma and benign exemplars, as chosen by experts, increased specificity and diagnostic accuracy. The ABCD method and use of melanoma exemplar images chosen by laypersons decreased specificity in comparison with the control. The method of choosing exemplar images is important. The levels of change in performance are however very modest, with an increase in accuracy between control and best-performing strategy of only 9%.

Robust experimental evidence supporting many attempts to facilitate early melanoma diagnosis is lacking. In an experimental study using a browser interface we have examined diagnostic accuracy, sensitivity and specificity of novices in distinguishing between melanomas and mimics of melanoma. We show that rule-based ABC methods and image training, based on random images of melanoma, improve specificity to similar degrees, with-out effects on sensitivity, leading to small improvements in overall accuracy. There was a significant effect of age with older subjects performing better. Although both the ABC method and image training groups showed improved performance over the control group, overall performance was poor. For instance, for a task in which 1 in 4 test images was a melanoma, and 3 out of 4 benign, both interventions (ABC or image training) increased accuracy from the control value of 53% to around 61%. For reference, dermatology trainees performed at a much higher level of accuracy. Our study provides little support for the use of such methods in public education, but suggests ways in which performance might be improved.

Traditional clinical teaching emphasises the importance of a full clinical examination. In the clinical assessment of lesions that may be skin cancer, full examination allows detection of incidental lesions, as well as helping in the characterisation of the index lesion. Despite this, a total body skin examination is not always performed. Based on two prospective studies of over 1,800 sequential patients in two UK centres we show that over one third of melanomas detected in secondary care are found as incidental lesions, in patients referred for assessment of other potential skin cancers. The majority of these melanomas occurred in patients whose index lesion turned out to be benign. Alternative models of care--for instance some models of teledermatology in which a total body skin examination is not performed by a competent practitioner--cannot be considered equivalent to a traditional consultation and, if adopted uncritically, without system change, will likely lead to melanomas being missed.

Background: Skin cancers are the most common malignancies in Caucasian populations. Non-specialists are responsible for the initial assessment of skin lesions and are required to act as the gatekeepers to dermatological cancer services in many healthcare systems. The majority of such physicians receive very limited formal undergraduate or postgraduate dermatology training. The British Association of Dermatologists (BAD) has produced guidelines that list the lesions that students should be able to diagnose on graduation and the majority of UK medical schools' operate curricula in keeping with these. There is, however, virtually no evidence as to whether these competencies are being achieved. We set out to determine students' competence at skin lesion diagnosis and to quantify their clinical exposure to examples of such lesions during their dermatology attachment., Methods: Three linked studies were undertaken. In the first, students' competence was tested by randomized slideshows of images containing the 16 lesions recommended in the UK guidelines. Students' accuracy was tested at the beginning (Day 1) and end (Day 10) of their clinical placement, with a random sample of students retested 12 months later. Secondly, students' exposure to these lesions was recorded during their attachments. Finally a survey of the additional dermatological resources used by the students was undertaken., Results: Study 1: Students' diagnostic accuracy increased from 11% on Day 1 to 33% on Day 10 (effect size +2.72). After 12 months half of this effect had disappeared and the students accuracy had dropped to 24%. Study 2: Students' exposure to the recommended lesions was poor with 82% not even witnessing a single example of each of the 3 major skin cancers. Despite these measurements, only a minority of students reported that they were not confident at diagnosing skin tumours. Study 3: The majority of students use additional resources to supplement their learning., Conclusions: In the light of what we know about learning in dermatology, our data would suggest, that the current (traditional) undergraduate attachment is inadequate to meet the UK recommendations for graduate competence. As well as critically examining the basis for these recommendations, we need more empirical data on student performance and exposure, in order to improve teaching and learning.

The "ABCD" mnemonic to assist non-experts' diagnosis of melanoma is widely promoted; however, there are good reasons to be sceptical about public education strategies based on analytical, rule-based approaches--such as ABCD (i.e. Asymmetry, Border Irregularity, Colour Uniformity and Diameter). Evidence suggests that accurate diagnosis of skin lesions is achieved predominately through non-analytical pattern recognition (via training examples) and not by rule-based algorithms. If the ABCD are to function as a useful public education tool they must be used reliably by untrained novices, with low inter-observer and intra-diagnosis variation, but with maximal inter-diagnosis differences. The three subjective properties (the ABCs of the ABCD) were investigated experimentally: 33 laypersons scored 40 randomly selected lesions (10 lesions × 4 diagnoses: benign naevi, dysplastic naevi, melanomas, seborrhoeic keratoses) for the three properties on visual analogue scales. The results (n = 3,960) suggest that novices cannot use the ABCs reliably to discern benign from malignant lesions.

Reduced function alleles of the melanocortin 1 receptor (MC1R) lead to red hair, freckling, and sun sensitivity. They are also associated with an increased risk of skin cancer. But what pathways link gene variants with the cancer phenotype? In this issue, Robinson et al. describe their use of mouse transgenics to demonstrate that the MC1R signaling pathway influences cancer risk via mechanisms in addition to pigmentation.

Humans vary >100-fold in their sensitivity to the harmful effects of ultraviolet radiation. The main determinants of sensitivity are melanin pigmentation and less-well-characterized differences in skin inflammation and repair processes. Pigmentation has a high heritability, but susceptibility to cancers of the skin, a key marker of sun sensitivity, is less heritable. Despite a large number of murine coat-color mutations, only one gene in humans, the melanocortin 1 receptor (MC1R), is known to account for substantial variation in skin and hair color and in skin cancer incidence. MC1R encodes a 317-amino acid G-coupled receptor that controls the relative amounts of the two major melanin classes, eumelanin and pheomelanin. Most persons with red hair are homozygous for alleles of the MC1R gene that show varying degrees of diminished function. More than 65 human MC1R alleles with nonsynonymous changes have been identified, and current evidence suggests that many of them vary in their physiological activity, such that a graded series of responses can be achieved on the basis of (i) dosage effects (of one or two alleles) and (ii) individual differences in the pharmacological profile in response to ligand. Thus, a single locus, identified within a Mendelian framework, can contribute significantly to human pigmentary variation.

p21WAF is a cyclin-dependent kinase inhibitor which is widely expressed in epidermal structures. Using a combination of double immunocytochemical staining and combined in situ hybridization, we show that there is a striking exclusivity between the expression of Ki67 and p21WAF in the hair matrix. Some cells that are Ki67-positive also express p53, but as they exit the cell cycle they assume p21WAF-positive/p53-negative status. By contrast, cells in the interfollicular epidermis of psoriatic lesions, in the sebaceous gland, and in the outer root sheath are p21WAF-positive/p53-positive but Ki67-negative. These results suggest that in some anatomical parts of the epidermis, p21WAF expression can accompany p53 expression, whereas in other parts, the expression of these markers is reciprocal, suggesting that other pathways may be controlling p21WAF expression. In order to define, functionally, the presence of p53-independent p21WAF expression in skin, we examined lesions of Bowen's disease in which both alleles of p53 were inactivated. p21WAF expression was still observed, confirming a role for p53-independent expression of p21WAF in human skin in vivo.

Sun-exposed skin of Caucasians harbors thousands of p53-mutated clones, which are clinically invisible. Using whole mount immunostaining for p53 or Ki67 antigens, p53 sequencing, and loss of heterozygosity analysis, we have further characterised these clones. Loss of heterozygosity for the alleles examined is uncommon with the exception of 9q, which occurred in 28.3% of the samples. P53 clones are more common and larger in individuals with basal cell carcinoma than in control subjects (p < 0.03). Loss of heterozygosity is also more common in clones from individuals with basal cell carcinoma than in clones from subjects without a history of basal cell carcinoma, as would be expected if both relate to ultraviolet radiation exposure. p53 sequencing of clones is in keeping with the mutagenic role of ultraviolet radiation. Surprisingly, skin found to harbor p53 clones showed no clusters of Ki67 positive cells, unlike the situation for actinic keratoses or basal cell carcinomas. These results show that in human skin p53 mutation is not directly associated with genomic instability or abnormal cell cycling; that the p53 immunopositive clones are either genetically distinct or precursors to other squamous cell lesions of skin; and that p53 immunopositive clones are early lesions, in that gross disturbance of proliferation has not already occurred.

Loss of genetic material, including loss of loci on chromosome arms 6q, 9p, and 10q, occurs frequently in cutaneous melanoma but infrequently in benign melanocytic nevi or other melanocytic lesions, suggesting that these genetic alterations are important in the development and progression of melanoma. To examine whether allelic loss is of prognostic importance in melanoma, disease-free survival was related to loss of heterozygosity on 6q, 9p and 10q in 83 individuals with sporadic primary cutaneous melanoma. Loss of chromosome arms 6q and 10q were each significantly associated with a poorer clinical outcome (P=0.013 and P=0.001 respectively). In a subgroup of 41 subjects whose primary tumours were allelotyped, the fractional allelic loss (FAL) at 39 autosomal arms also significantly correlated with disease-free survival (P=0.013), with an increase in FAL associated with a poorer outcome; this association remained significant when controlled for tumour thickness (P=0.035). In addition, a greater proportion of cells were immunopositive for Ki67 antigen, p53 and p21WAF1 protein in the primary melanomas than in the benign melanocytic nevi, however, only p53 over-expression was significantly associated with improved survival (P=0.041).

The genetic events responsible for tumor progression may be defined by careful analysis of genetic changes in well-chosen tumors which contain distinct cell populations representing each stage of progression. Here we report a case of a trichilemmal carcinoma arising in the wall of a proliferating trichilemmal cyst (PTC). DNA was isolated from microdissected areas of the PTC and the carcinoma respectively, and PCR-based microsatellite loss of heterozygosity (LOH) analysis as well as p53 gene sequencing performed. A CGA to TGA nonsense mutation at codon 306 in exon 8 of the p53 gene was found in both samples. LOH analysis showed that the PTC retained chromosome arm 17p (where the p53 gene resides), whereas the carcinoma was associated with the loss of this allele. All the other loci examined were retained including 3p, 9q, 13q and 17q in both tumor parts. The results confirm a common clonal origin of the PTC and the trichilemmal carcinoma, and strongly suggest that the complete loss of the wild-type p53 is a critical event responsible for malignant transformation in this particular case.

Loss of heterozygosity of chromosomes 3p and 13q occurs frequently in human cutaneous squamous cell neoplasms, suggesting the presence of one or more tumor suppressor genes on these chromosome arms that may be involved in the pathogenesis of this tumor type. To date there is no clear evidence in cutaneous tumors where these putative genes are located. In this study we have analyzed 20 squamous cell neoplasms that show allelic loss at chromosome 13q, and 22 squamous cell neoplasms that show allelic loss at chromosome 3p, in an attempt to define the smallest area of deletion. One commonly deleted region was identified on chromosome 13 that centred around 13q13, and two commonly deleted regions were identified on chromosome 3 that mapped to 3p24-pter and 3p12-p14.1. Our findings suggest the presence of at least one tumor suppressor gene on chromosome 13 and two tumor suppressor genes on chromosome 3p that may be involved in the progression of these neoplasms. Deletions within the Fragile Histidine Triad gene, located at 3p14.2, have been reported in several tumors, leading to the suggestion that this gene is involved in tumor development. To evaluate the role of the Fragile Histidine Triad gene in nonmelanoma skin cancer, we have used reverse transcriptase polymerase chain reaction analysis to screen for deletions in 16 tumors (five basal cell carcinomas, five squamous cell carcinomas, five actinic keratoses, and one case of Bowen's disease) and HaCaT and A431 cell lines. A normal transcript was found to be expressed in 14 of 16 tumors and both cell lines. This suggests that the Fragile Histidine Triad gene is not a common target for deletion in Bowen's disease and the cell lines HaCaT and A431.

Cutaneous pigmentation is a major determinant of the cutaneous response to ultraviolet radiation, and consequently of the risk of developing skin cancer. Over the past 10 years, several genes involved in melanogenesis have been identified, including the melanocortin 1 receptor gene. Recent work on the melanocortin 1 receptor suggests that it is a key player in determining whether eumelanin or pheomelanin is predominantly produced both in vitro and in vivo. In the mouse, variants of this receptor, which differ in their ability to activate adenylyl cyclase, are associated with different coat colors. In humans, melanocortin 1 receptor variants are associated with red hair and fair skin, and work in progress from our laboratory suggests that certain melanocortin 1 receptor variants may preferentially be associated with hair color rather than skin type. In addition, melanocortin 1 receptor variants are a risk factor, possibly independent of skin type, for melanoma susceptibility.

The Japanese have a much lower incidence of nonmelanoma skin cancers (NMSCs) than Caucasians, presumably due in part to their skin type conferring relative protection from ultraviolet light radiation (UVR). To examine the contribution of environmental or endogenous mutagens other than UVR, which are expected to be relatively more important to the overall burden of NMSCs in the Japanese, we directly sequenced exons 5-8 of the p53 tumour suppressor gene in 29 Japanese patients with Bowen's disease, an in situ squamous-cell carcinoma of the skin. We found 9 mutations, including two CC:GG to TT:AA tandem transitions (presumably related to UVR), 3 transversions and 4 frameshift mutations. The mutational spectrum seen in our study contrasts with that we previously found in Bowen's disease from a Caucasian population, in keeping with a different aetiology for Bowen's disease in the respective populations. The unexpectedly high prevalence of frameshift mutations suggests that environmental mutagens other than UVR that preferentially induce deletion or insertion mutations may play an important role in the tumorigenesis of Japanese Bowen's disease, and warrants further investigation.

Organ transplant recipients receiving immunosuppression show a dramatically increased risk of non-melanoma skin cancer. The cause of this increase is not known. We report that the rate of loss of heterozygosity (at all the loci we examined) was significantly lower in tumours from immunosuppressed individuals than in tumours from immunocompetent subjects [20 out of 148 (14%) vs 157 out of 428 (37%); P< 0.0001]. These results suggest that tumours in immunosuppressed individuals have a different molecular pathogenesis.

Loss of heterozygosity of chromosome region 9p21 occurs commonly and early in sporadic melanoma, suggesting the involvement of a tumor suppressor gene at this locus in the pathogenesis of this neoplasm. Although germline mutations and deletions of the p16INK4 gene located at 9p21 have been reported in familial melanoma, the relative contributions of mutation and deletion in sporadic melanoma are at present unclear. In this study, we investigated 26 cases of sporadic cutaneous melanoma (14 of which demonstrated loss of heterozygosity at 9p21) for mutations of p16INK4. One tumor with allelic loss of 9p contained a CC-->TT mutation at codons 57/58, altering an arginine to a stop codon, consistent with bi-allelic inactivation of p16INK4 in this case. No mutations were identified in any of the other melanomas, or in one benign intradermal nevus with atypical features and two Spitz nevi that also showed loss of heterozygosity of 9p. The inactivation of both copies of p16INK4 in the one case of melanoma adds support to the theory that p16INK4 is important in the development of sporadic cutaneous melanoma, although allelic loss or other methods of inactivation of p16INK4 rather than point mutation appears to be numerically more important. The low frequency of mutation of p16INK4 in cases of sporadic melanoma with loss of heterozygosity of 9p is, however, also consistent with there being another tumor suppressor gene near this locus that is involved in some cases of sporadic melanoma.

Previous studies of loss heterozygosity (LOH) have revealed distinct patterns of allelic loss in some skin tumors. In basal cell carcinomas (BCCs) loss of heterozygosity is virtually restricted to chromosome 9, whereas in squamous cell carcinomas (SCCs) and actinic keratoses loss is more widespread involving chromosomes 3, 9, 13, and 17. Because there are histological similarities between BCCs and some appendageal tumors, and because lines of evidence suggest that BCCs are appendageal in origin, we carried out a limited allelotype in 41 appendageal tumors. The overall frequency of allelic loss was low (4 out of 247 informative loci; 1.6%). LOH was seen in a proliferating trichilemmal cyst (17p), a sebaceous epithelioma (17q), an eccrine porocarcinoma (17q), a trichoepithelioma (9q), and in two basal cell carcinomas showing eccrine or granular cell differentiation that were originally misdiagnosed (9Q). The pattern of loss in this mixed group of appendageal tumors shows differences from both BCCs and SCCs, and further emphasizes the unique genetic profile and behavior of BCCs. The finding of 9q loss in BCCs with eccrine or granular cell differentiation shows that 9q loss occurs in differential histological subtypes of BCCs.

An 8-year-old boy presented with a 10-week history of ulcerating lesions which were histologically and immunocytochemically consistent with the diagnosis of angiocentric T-cell lymphoma. The disease was limited to the skin and resolved with no chemotherapy. Angiocentric T-cell lymphoma is commonly a disease with considerable morbidity and is often fatal. Epstein-Barr virus (EBV) could not be identified in involved tissue by immunostaining or by in situ hybridization. We consider whether the uncharacteristic absence of EBV in this case has prognostic significance.

Keratoacanthomas (KAs) resemble squamous cell carcinomas (SCCs) except that, unlike SCCs, after a period of rapid growth over a few months they involute completely. The basis of their regressing natural history is not known. We have examined keratoacanthomas and another benign cutaneous tumour, the basal cell papilloma (BCP), for loss of heterozygosity (LOH) at a number of loci that are frequently lost in SCCs and other skin tumours. The frequency of LOH for both KAs and BCPs was low, with only isolated losses identified at 9p, 9q and 10q in KAs [fractional allelic loss (FAL) was 1.3%], and at 9p and 17p in BCPs (FAL was 0.4%). This contrasts with previous work showing a FAL of 32% in SCC and 46% in actinic keratoses. The results show a clear difference between KA and SCC and do not support the hypothesis that KAs are SCCs that regress as a result of external (host) influences but rather suggest that KAs and SCCs are different de novo. LOH around the locus implicated in the multiple self-healing epitheliomata of Ferguson-Smith (9q22-q31) was shown in only 1 of 11 KAs.

A multistep genetic model of tumorigenesis, based on genetic alterations in benign and primary malignant lesions, has been proposed for neoplasms such as colonic carcinoma. However, evidence for a similar genetic progression in melanoma has relied heavily on findings in cultured lesions or metastases. We have investigated every autosomal arm for loss of heterozygosity in 41 primary cutaneous melanomas and 32 benign melanocytic nevi, and have investigated several chromosome arms that show loss in melanoma in 27 Spitz nevi (a nevus with histological similarities to melanoma). Loss of heterozygosity in primary melanoma was identified most frequently on chromosomes 9p (46%) at loci near the p16INK4 gene, 10q (31%), 6q (31%), and 18q (22%); loss of these chromosome arms were related to the progression of the melanoma. Only two benign melanocytic nevi (both of which showed atypical features on histology) demonstrated genetic alterations, including p9 loss in one case. In addition, two Spitz nevi contained interstitial deletions on chromosome 9p. Our findings show that loss of heterozygosity of 9p is not confined to melanoma, but that other uncultured melanocytic lesions can also display loss of this chromosome arm, and that other genetic changes (e.g., loss of 10q, 6q, and 18q) may be important in conveying the malignant phenotype to melanoma.

Recurrence of basal cell carcinoma (BCC) following treatment is a common event and long-term follow-up of all patients presenting with a primary BCC has been recommended. Proliferation indices have been recognized as important prognostic factors in several tumour types in a variety of cancer systems, being significantly elevated in more aggressive lesions. We have examined 51 BCCs (17 non-recurrent tumours [group 1], 17 original tumours which later recurred [group 2-O], and the corresponding 17 recurrent specimens [group 2-R]) for Ki67 antigen expression, a proliferation-associated antigen using immunohistochemistry with the monoclonal antibody MIB1. There was a significant increase in the percentage positive for MIB1 in the Group 2-O as compared with the group 1 BCCs (P < 0.05). p53 protein expression, as assessed by immunohistochemistry with the monoclonal antibody DO7, was similar in each group. These results show that Ki67 antigen expression differs between BCCs which later recur and BCCs that do not recur.

Microsatellite instability secondary to replication errors (RER), characterized by length changes at repetitive loci scattered throughout the genome, is a recently recognized genetic mechanism important in the development of some human cancers. Although RER has been reported in sebaceous gland tumors from patients with the Muir-Torre syndrome, the frequency of RER in human non-melanoma and melanoma skin cancers is not known. In this study, we investigated the importance of RER in human skin carcinogenesis. RER was identified in three of four actinic keratoses from a patient belonging to a kindred with documented Muir-Torre syndrome, which indicates that defective DNA replication may contribute to skin cancer development in such patients. Examination of a series of tumors from patients without Muir-Torre, including 137 skin cancers (47 basal cell carcinomas, 49 squamous cell carcinomas, and 41 primary malignant melanomas), 19 actinic keratoses, and 20 cases of Bowen's disease, using 10 or more microsatellite markers, identified repeat-sequence instability in less than 5% of the tumors studied. In six of the eight tumors, the sole change was an alteration 2 base pairs in length at a single locus. One patient with a squamous cell carcinoma showed changes at multiple loci suggesting defective mismatch repair. Although the low frequency of RER found in this study of a large series of human skin tumors suggests that this phenomenon is uncommon in patients with skin cancer, the identification of RER at multiple loci in two patients suggests that error-prone replication may be important in skin cancer development in some individuals.

Basal cell carcinomas (BCC) and squamous cell carcinomas (SCC) show clinical and epidemiological differences not accounted for by different ultraviolet radiation exposure. We have studied experimentally induced contact sensitivity to dinitrochlorobenzene by measuring increases in skin-fold thickness. Patients (n = 37) with squamous tumours had impaired responses compared with controls (33) and patients with BCCs (31) (mean increase 4.5 vs 7.8 and 8.6 mm, respectively; p = 0.002). This diminished immunological response may be causally related to the development of SCC. Because glutathione S-transferase (GST) metabolises dinitrochlorobenzene and polymorphisms of GST are associated with multiple skin tumours, variations in GST may underlie these differences.

Difficulties in obtaining clinical samples from primary melanomas have meant that most genetic analyses of melanoma have concentrated on cell lines and metastases. Because the Breslow thickness of the primary tumour is the single best prognostic indicator, it is important to identify genetic abnormalities in primary melanomas and relate these changes to the thickness of the lesion. We have investigated 47 sporadic melanomas, of which 41 were primary lesions, for loss of heterozygosity (LOH) on several chromosomal arms, including areas where genes involved in familial melanoma and other relevant hereditary syndromes map, and where LOH has previously been reported in cell lines, or metastatic lesions. LOH was identified at 66 (18%) of 358 informative loci in primary melanomas, and there was a significant relationship between the overall frequency of LOH and Breslow thickness (P < 0.0005). Loss of chromosome arm 9p was most frequent, occurring in 15 (47%) of 32 informative primary tumours, and was observed in 3 of 11 informative lesions < or = 1.5 mm in depth. LOH on chromosome arms 3p, 6q, 10q, 11q, and 17p was also relatively frequent, with loss of 3p and 10q heterozygosity in lesions < or = 1.5 mm in depth, while LOH on 6q, 11q, and 17p was only detected in more invasive tumours. The results suggest that loss of these chromosome regions are important in sporadic cutaneous melanoma, and are consistent with chromosome arm 9p loss occurring before loss of other chromosome arms.

Human telomeres consist of arrays of the sequence TTAGGG up to 15-20 kb in length, which are essential for the maintenance of normal chromosomal stability. It has been suggested that genomic instability observed in tumours may be due to loss of telomere sequences. Somatic cells that are dividing continuously appear to progressively lose telomere sequences, and it would therefore be anticipated that cell type specific differences in mean telomere length may exist within an individual. Previous reports have suggested that mean telomere length may be different in human neoplasia when compared to control. Basal cell carcinomas are epidermal derived tumours and in order therefore to make valid cell type specific comparisons we have measured mean telomere length in 20 basal cell carcinomas as well as in both adjacent epidermis and dermis. Mean telomere length was significantly reduced in epidermis in comparison with dermis, from clinically normal skin immediately adjacent to the tumours (mean difference 2.5 kb). This result is not related to the presence of the tumour as similar results were obtained from skin samples of healthy volunteers. Basal cell carcinomas showed increased mean telomere length in 13/20 samples in comparison with matched epidermis (mean difference 3.1 kb), whereas in 7/20 mean telomere length was reduced (mean difference 2.2 kb). These results showing that mean telomere length varies from cell type to cell type underpin the importance of performing cell type specific controls when assessing changes in tumour telomeres.

The mapping of the naevoid basal cell carcinoma syndrome (NBCCS) and the Ferguson-Smith syndrome to the same region on chromosome arm 9q has led to speculation that the two conditions may reflect different mutations within the same gene. Loss of heterozygosity of 9q alleles in both familial and sporadic basal cell carcinomas (BCCs) suggests that the NBCCS gene on 9q is acting as a tumour suppressor gene. Although LOH of 9q markers has not been studied in squamous cell neoplasms from patients with the Ferguson-Smith syndrome, chromosome 9 allele loss has been reported in sporadic squamous cell carcinomas (SCCs) of the skin. In order to characterise further the deleted region on chromosome 9 in BCCs and SCCs of the skin we have examined a series of non-melanoma skin cancers using a panel of highly informative microsatellite markers. Forty-four BCCs and 49 SCCs were studied. Loss of heterozygosity of one or more 9q markers was seen in 33 of the 44 BCCs. Only 4 of the 33 BCCs with 9q loss showed loss of 9p markers. Twenty-two BCCs showed loss of all informative 9q markers. Partial or interstitial 9q deletions were seen in 5 BCCs, and in 3 of these 5 BCCs the breakpoint occurred within the currently defined NBCCS locus. Chromosome 9 loss was seen in 16 of 49 SCCs. In contrast to the low frequency of 9p loss in BCCs, LOH of 9p markers was a common finding in SCCs, occurring in 15 of the 16 SCCs with chromosome 9 loss. In 5 SCCs 9p loss occurred with retention of 9q alleles.(ABSTRACT TRUNCATED AT 250 WORDS)

Although basal cell carcinomas and squamous cell carcinomas are clinically and pathologically distinct, the molecular basis for these differences is not clear. We have used polymorphic microsatellite markers to determine the pattern and extent of chromosome losses in a series of 44 basal cell carcinomas and 47 squamous cell neoplasms of the skin. Basal cell carcinomas showed a distinctive allelotype with chromosome loss largely confined to a single chromosome arm, 9q (26 of 44 informative tumors). In contrast to the predominance of loss on a single chromosome arm in basal cell carcinomas, squamous cell neoplasms showed more widespread loss with loss of heterozygosity of markers from 35 of 39 chromosome arms in one or more of the tumors studied. The pattern of loss was also different from basal cell carcinomas with frequent loss of heterozygosity of markers from 9p (41%), 13q (46%), 17p (33%), 17q (33%), and 3p (23%) in squamous cell neoplasms. The frequent loss of markers from these chromosome arms relative to other chromosome losses suggests that these arms may contain genes important in the development of cutaneous squamous cell carcinomas.

Linkage studies of kindreds with the nevoid basal cell carcinoma syndrome and the high frequency of chromosome 9 allele loss in sporadic basal cell carcinomas indicate that chromosome 9 may contain tumor suppressor genes important in the development of sporadic and familial basal cell carcinomas. The recent mapping of the Ferguson-Smith syndrome, which predisposes affected individuals to the development of multiple lesions histologically indistinguishable from squamous cell carcinomas, suggests that tumor suppressor genes on 9q may also be important in the development of squamous cell neoplasms of the skin. Fifty-four non-melanoma skin cancers (24 basal cell carcinomas, 14 squamous cell carcinomas, and 16 cases of Bowen's disease) were examined for loss of heterozygosity on chromosome 9. Allelic loss at one or more loci on chromosome 9 was observed in 14 of 24 basal cell carcinomas, four of 14 squamous cell carcinomas, and three of 16 cases of Bowen's disease. Allelic deletion of one or more 9q markers was seen in 14 basal cell carcinomas, three squamous cell carcinomas, and three cases of Bowen's disease. Five basal cell carcinomas had interstitial deletions and in one the breakpoint mapped within the nevoid basal cell carcinoma syndrome locus. 9p loss occurred in three of nine informative squamous cell carcinomas. Allelic deletion of 9p markers was not seen in 19 basal cell carcinomas and seven cases of Bowen's disease. These findings suggest that chromosome 9 contains one or more tumor suppressor genes important in the development of both basal and squamous cell carcinomas of the skin.

Extensive study of the p53 gene has established its role as a tumour-suppressor gene, and the involvement of mutant p53 in a wide spectrum of human malignancy. Many mutations of p53 result in a protein product that is abnormally stable, so that it becomes readily detectable by immunocytochemistry. In contrast, under normal conditions, it has been considered that levels of wild-type p53 were too low to be detectable. Although positive immunocytochemistry has been used as a marker of mutation, recent evidence suggests that this assumption may not always be valid. We have carried out both PCR-sequencing of exons 5-8 of the p53 gene in 20 basal cell carcinomas (BCC), and immunocytochemistry of these tumours with the anti-p53 antibody DO7. Twenty cases of Bowen's disease, in which we had previously documented mutations, were also immunostained. We report a low rate of p53 mutation in the BCCs we examined (2/20), and a discrepancy between tumours with positive immunostaining and those with mutation in both Bowen's disease and BCC. Of eight tumours in which we detected mutation, only four were immunopositive: of 19 immunopositive samples, only four showed detectable mutation. We discuss the implications of our results for the use of positive immunostaining in clinical diagnosis, and the involvement of p53 in skin carcinogenesis.

Mutations of the p53 gene are the most common genetic abnormality described in human cancer; p53 mutations have recently been reported in more than half of the cases of squamous cell carcinomas of the skin. We have previously reported positive p53 immunostaining in Bowen's disease and actinic keratosis. To determine if this abnormal immunostaining reflects p53 mutation or alternative pathways of p53 protein inactivation we have performed direct sequencing of p53 in 20 further cases of Bowen's disease. We found eight mutations in 20 cases, seven of which would produce alterations in the p53 protein product. Our results suggest that p53 mutation is an early event in malignant conversion, frequently preceding invasion in squamous cell neoplasia of the skin. The type and site of the observed mutations reflect known mutational hotspots and support the role of ultraviolet radiation in the pathogenesis of these tumors.

The skin affords an excellent model of human carcinogenesis because a variety of lesions from benign tumours to invasive malignancy, with or without metastatic potential, are commonly found, and are accessible to biopsy. To date, few genetic alterations have been observed in skin neoplasia. In this study we have used a recently developed monoclonal antibody (DO7) to examine p53 protein expression in a wide variety of benign and malignant skin lesions. Benign skin lesions were negative, but a significant number of malignant epithelial lesions showed detectable p53; 56% of squamous carcinomas and 42% of basal cell carcinomas were positive. A smaller proportion of dysplastic epithelial lesions were positive (27%), and only 3.6% of malignant melanomas were positive. Thus, although detectable p53 protein is a common occurrence in malignant epithelial lesions, it does not correlate with the malignant phenotype or with metastatic potential. The finding of a lower proportion of positivity in dysplastic lesions, and absence of staining in benign tumours, suggests that p53 mutation may be involved in the progression towards invasive malignancy in human squamous skin lesions.

ras mutations have been reported as an early event in some human malignancies and in the mouse skin model of multistep carcinogenesis; early studies in human non-melanoma skin cancers have reported variable rates of ras mutations. A recent study, however, has reported a high frequency of activating mutations of the Harvey-ras proto-oncogene in non-melanoma skin cancers, and the site specificity of the mutation at the second position of codon 12 prompted us to re-examine the importance of Ha-ras codon 12 mutations as an early event in the development of these tumours, using a combination of PCR and restriction fragment polymorphism of codon 12 of the Ha-ras gene. Dilution experiments confirmed that the method was sensitive and capable of detecting mutations at this codon when only 4% of the total alleles are mutated. We were surprised to find no mutations in the 40 basal cell carcinomas, 12 squamous cell carcinomas and 12 cases of Bowen's disease studied. We conclude that Ha-ras codon 12 mutations are rare events in human non-melanoma skin cancer in the U.K. The marked differences in the frequency of codon 12 Ha-ras mutations in published studies may relate to either technical artefacts, or differences in the molecular epidemiology between areas of low and high sun exposure.