Terahertz in vivo imaging of human skin: Toward detection of abnormal skin pathologies.

Terahertz (THz) imaging has long held promise for skin cancer detection but has been hampered by the lack of practical technological implementation. In this article, we introduce a technique for discriminating several skin pathologies using a coherent THz confocal system based on a THz quantum cascade laser. High resolution in vivo THz images (with diffraction limited to the order of 100 µm) of several different lesion types were acquired and compared against one another using the amplitude and phase values. Our system successfully separated pathologies using a combination of phase and amplitude information and their respective surface textures. The large scan field (50 × 40 mm) of the system allows macroscopic visualization of several skin lesions in a single frame. Utilizing THz imaging for dermatological assessment of skin lesions offers substantial additional diagnostic value for clinicians. THz images contain information complementary to the information contained in the conventional digital images.

A robust experimental and computational analysis framework at multiple resolutions, modalities and coverages.

The ability to study cancer-immune cell communication across the whole tumor section without tissue dissociation is needed, especially for cancer immunotherapy development, which requires understanding of molecular mechanisms and discovery of more druggable targets. In this work, we assembled and evaluated an integrated experimental framework and analytical process to enable genome-wide scale discovery of ligand-receptors potentially used for cellular crosstalks, followed by targeted validation. We assessed the complementarity of four different technologies: single-cell RNA sequencing and Spatial transcriptomic (measuring over >20,000 genes), RNA In Situ Hybridization (RNAscope, measuring 4-12 genes) and Opal Polaris multiplex protein staining (4-9 proteins). To utilize the multimodal data, we implemented existing methods and also developed STRISH (Spatial TRanscriptomic In Situ Hybridization), a computational method that can automatically scan across the whole tissue section for local expression of gene (e.g. RNAscope data) and/or protein markers (e.g. Polaris data) to recapitulate an interaction landscape across the whole tissue. We evaluated the approach to discover and validate cell-cell interaction in situ through in-depth analysis of two types of cancer, basal cell carcinoma and squamous cell carcinoma, which account for over 70% of cancer cases. We showed that inference of cell-cell interactions using scRNA-seq data can misdetect or detect false positive interactions. Spatial transcriptomics still suffers from misdetecting lowly expressed ligand-receptor interactions, but reduces false discovery. RNAscope and Polaris are sensitive methods for defining the location of potential ligand receptor interactions, and the STRISH program can determine the probability that local gene co-expression reflects true cell-cell interaction. We expect that the approach described here will be widely applied to discover and validate ligand receptor interaction in different types of solid cancer tumors.

High variability in anatomic patterns of cutaneous photodamage: a population-based study.

BACKGROUND: Skin cancer is strongly associated with photodamaged skin, but body sites are often referred to as 'exposed' or 'unexposed' to sun without recognizing extent of site-specific variation. OBJECTIVES: To assess whole-body patterns of photodamage in an Australian population. METHODS: A random sample of adult residents of Queensland underwent imaging across 10 body sites. Photodamage was graded from images using an ordinal photonumeric scale. We used cluster analysis to identify whole-body photodamage patterns and prevalence proportion ratios (PPRs) to assess associated factors. RESULTS: Of 190 adults (median age 52; 58% males), 58% showed severe or moderate-to-severe photodamage on most body sites. A higher proportion of woman had severe photodamage on the arms (upper: P = 0.002, lower: P = 0.034). A higher proportion of men had moderate or severe photodamage on the lower back (P = 0.004). We identified four photodamage patterns: 'severe general' (n = 24, 13%), 'moderate-severe general' (n = 86, 45%), 'moderate-severe v-neck' (n = 40, 21%) and 'mild-moderate upper body' (n = 12, 6%). All participants with 'severe-general' photodamage were >50 years and more likely to have past skin cancer (PPR: 2.54, 95% CI: 1.44-4.49) than those with 'moderate-severe v-neck' photodamage. Those with 'moderate-severe general' photodamage showed similar associations and were more likely female (PPR: 1.33, 95% CI: 1.04-1.69). Past or current smoking was associated with having higher levels of photodamage, with no smokers in those with 'mild-moderate upper body' photodamage. CONCLUSIONS: Moderate-to-severe photodamage across much of the body is common in Queensland adults and associated with age, sex, past skin cancer and smoking. Assuming a universal pattern of site-specific sun exposure could lead to spurious correlations, while accurate and objective assessment of site-specific photodamage can add to understanding of the development of sun-associated skin cancers, in particular site-specific skin carcinogenesis. Additionally, degree of site-specific photodamage has the potential to assist skin cancer screening.

Estimating the potential impact of interventions to reduce over-calling and under-calling of melanoma.

BACKGROUND: Pathologists sometimes disagree over the histopathologic diagnosis of melanoma. 'Over-calling' and 'under-calling' of melanoma may harm individuals and healthcare systems. OBJECTIVES: To estimate the extent of 'over-calling' and 'under-calling' of melanoma for a population undergoing one excision per person and to model the impact of potential solutions. METHODS: In this epidemiological modelling study, we undertook simulations using published data on the prevalence and diagnostic accuracy of melanocytic histopathology in the U.S. POPULATION: We simulated results for 10 000 patients each undergoing excision of one melanocytic lesion, interpreted by one community pathologist. We repeated the simulation using a hypothetical intervention that improves diagnostic agreement between community pathologist and a specialist dermatopathologist. We then evaluated four scenarios for how melanocytic lesions judged to be neither clearly benign (post-test probability of melanoma < 5%), nor clearly malignant (post-test probability of melanoma > 90%) might be handled, before sending for expert dermatopathologist review to decide the final diagnosis. These were (1) no intervention before expert review, (2) formal second community pathologist review, (3) intervention to increase diagnostic agreement and (4) both the intervention and formal second community pathologist review. The main outcomes were the probability of 'over-calling' and 'under-calling' melanoma, and number of lesions requiring expert referral for each scenario. RESULTS: For 10 000 individuals undergoing excision of one melanocytic lesion, interpreted by a community pathologist, a hypothetical intervention to improve histopathology agreement reduced the number of benign lesions 'over-called' as melanoma from 308 to 164 and the number of melanomas 'under-called' from 289 to 240. If all uncertain diagnoses were sent for expert review, the number of referrals would decrease from 1500 to 737 cases if formal second community pathologist review was used, and to 701 cases if the hypothetical intervention was additionally used. CONCLUSIONS: Interventions to improve histopathology agreement may reduce melanoma 'over-calling' and 'under-calling'.

Clinical utility of skin cancer and melanoma risk scores for population screening: TRoPICS study.

BACKGROUND: Screening for skin cancer can be cost-effective if focused on high-risk groups. Risk prediction tools have been developed for keratinocyte cancers and melanoma to optimize advice and management. However, few have been validated in a clinical setting over the past few years. OBJECTIVES: To assess the clinical utility of risk assessment tools to identify individuals with prevalent skin cancers in a volunteer-based screening clinic. METHODS: Participants were adults presenting for a skin check at a volunteer-based skin cancer screening facility. We used previously published tools, based on questionnaire responses, to predict melanoma and keratinocyte cancers [KCs; basal cell carcinoma (BCC) and squamous cell carcinoma (SCC)] and classified each participant into one of five risk categories. Participants subsequently underwent a full skin examination by a dermatologist. All suspicious lesions were biopsied, and all cancers were histopathologically confirmed. RESULTS: Of 789 people who presented to the clinic, 507 (64%) consented to the study. Twenty-two BCCs, 19 SCCs and eight melanomas were diagnosed. The proportion of keratinocyte cancers diagnosed increased according to risk category from <1% in the lowest to 24% in the highest risk category (P < 0.001). Subtype analysis revealed similar proportionate increases in BCC or SCC prevalence according to risk category. However, a similar proportion of melanoma cases were detected in the low-risk and high-risk groups. CONCLUSION: The risk prediction model for keratinocyte cancers can reliably identify individuals with a significant skin cancer burden prior to a skin examination in the community setting. The prediction tool for melanoma needs to be tested in a larger sample exposed to a wider range of environmental risk factors.

Human surface anatomy terminology for dermatology: a Delphi consensus from the International Skin Imaging Collaboration.

BACKGROUND: There is no internationally vetted set of anatomic terms to describe human surface anatomy. OBJECTIVE: To establish expert consensus on a standardized set of terms that describe clinically relevant human surface anatomy. METHODS: We conducted a Delphi consensus on surface anatomy terminology between July 2017 and July 2019. The initial survey included 385 anatomic terms, organized in seven levels of hierarchy. If agreement exceeded the 75% established threshold, the term was considered 'accepted' and included in the final list. Terms added by the participants were passed on to the next round of consensus. Terms with <75% agreement were included in subsequent surveys along with alternative terms proposed by participants until agreement was reached on all terms. RESULTS: The Delphi included 21 participants. We found consensus (≥75% agreement) on 361/385 (93.8%) terms and eliminated one term in the first round. Of 49 new terms suggested by participants, 45 were added via consensus. To adjust for a recently published International Classification of Diseases-Surface Topography list of terms, a third survey including 111 discrepant terms was sent to participants. Finally, a total of 513 terms reached agreement via the Delphi method. CONCLUSIONS: We have established a set of 513 clinically relevant terms for denoting human surface anatomy, towards the use of standardized terminology in dermatologic documentation.

Clinicopathological factors associated with death from thin (≤ 1·00 mm) melanoma.

BACKGROUND: Thin cutaneous melanomas (≤ 1·00 mm) are increasing worldwide, causing around a quarter of all melanoma deaths in the U.S.A. and Australia. Identification of predictive factors for potentially fatal thin melanomas could allow better use of resources for follow-up. OBJECTIVES: To identify the clinicopathological factors associated with fatal thin melanomas. METHODS: This large, nested case-case study extracted data from the population-based Queensland Cancer Registry, Australia. Our cohort consisted of Queensland residents aged 0-89 years who were diagnosed with a single, locally invasive thin melanoma (≤ 1·00 mm) between 1995 and 2014. Fatal cases (eligible patients who died from melanoma) were individually matched to three nonfatal cases (eligible patients who were not known to have died from melanoma) according to sex, age, year of diagnosis and follow-up interval. Using conditional logistic regression, we calculated odds ratios (ORs) for melanoma-specific death, adjusting for all collected clinicopathological variables. RESULTS: In the cohort, 27 660 eligible patients were diagnosed with a single, thin melanoma. The final case-case series included 424 fatal cases and 1189 nonfatal cases. Fatal cases were sixfold as likely to arise on the scalp as on the back [OR 6·39, 95% confidence interval (CI) 2·57-15·92] and six times as likely to be of thickness 0·80-1·00 mm as of < 0·30 mm (OR 6·00, 95% CI 3·55-10·17). CONCLUSIONS: Scalp location is a strong prognostic factor of death from thin melanoma. Further, this study provides support that melanomas with a thickness of 0·80-1·00 mm are the more hazardous thin lesions. Patients with these tumour characteristics require specific attention during follow-up. What's already known about this topic? Thin invasive melanomas (≤ 1·00 mm) contribute a substantial proportion of melanoma fatalities, owing to the high volume of disease. There is a need to find prognostic factors that will better identify fatal thin melanomas at the time of diagnosis. What does this study add? In this large population-based study, fatal thin tumours were sixfold as likely to be located on the scalp as on the back. Thin melanomas of 0·80-1·00 mm thickness were six times as likely to be associated with death as tumours < 0·30 mm. Scalp location and increasing thickness are strong predictive factors of fatal thin melanomas, indicating that patients with these tumour characteristics require close follow-up.

Skin cancer multiplicity in lung transplant recipients: a prospective population-based study.

BACKGROUND: Lung transplant recipients are at high risk of skin cancer, but precise annual incidence rates of treated skin cancers per patient are unknown. OBJECTIVES: To perform a prospective assessment of the total burden of histologically confirmed squamous cell carcinoma (SCC) and basal cell carcinoma (BCC) and associated factors in lung transplant recipients. METHODS: A population-based cohort of 125 Queensland lung transplant recipients aged 18 years and over, recruited between 2013 and 2015, were followed to the end of 2016. All underwent dermatological skin examinations at baseline and annually thereafter and patients self-reported all interim treated skin cancers, which were verified against pathology databases. Standard skin cancer risk factors were obtained via questionnaire, and details of medications were acquired from hospital records. RESULTS: During a median follow-up time of 1·7 years, 29 (23%) and 30 (24%) lung transplant recipients with a median duration of immunosuppression of 3·3 years developed SCC and BCC, respectively. The general population age-standardized incidence rates of SCC and BCC were 201 and 171 per 1000 person-years, respectively (based on first primary SCC or BCC during follow-up); however, on accounting for multiple primary tumours, corresponding incidence rates were 447 and 281 per 1000 person-years. Risk of multiple SCCs increased around sixfold in those aged ≥ 60 years and in those with previous skin cancer, and increased around threefold in those treated with the antifungal medication voriconazole. Multiple BCC risk rose threefold from age 60 years and tenfold for patients with previous skin cancer. CONCLUSIONS: Lung transplant recipients have very high incidence of multiple primary skin cancers. Close surveillance and assiduous prevention measures are essential. Linked Comment: Proby and Harwood. Br J Dermatol 2020; 183:416-417.

The interplay of sun damage and genetic risk in Australian multiple and single primary melanoma cases and controls.

BACKGROUND: Skin phenotype, host genotype and ultraviolet (UV) damage play a role in the development of melanoma. OBJECTIVES: To ascertain whether the level of UV damage at the site of melanomas was associated with genetic polymorphisms. METHODS: Deep phenotyping was performed on 1244 individuals; 281 with multiple primary melanomas (MPMs), 304 with single primary melanoma (SPM) and 659 convenience controls. Genotype data was generated using the Illumina CoreExome microarray platform, assaying over 500 000 single-nucleotide polymorphisms. A subset of variants were combined to assess a polygenic risk score (PRS) for melanoma. RESULTS: Most MPM cases were diagnosed in patients aged > 40 years, in sites with visible chronic UV damage. Women and those diagnosed at age ≤ 40 years were less likely to have perilesional UV damage. Patients with MPM had higher frequencies of MITF E318K, MC1R R-alleles and the ASIP risk haplotype. Individuals who had melanoma in a visibly UV-damaged site were more likely to carry MC1R rs75570604 [odds ratio (OR) 2·5], 9q31.2 rs10816595 (OR 1·4) and MTAP rs869329 (OR 1·4). These same alleles were more common in patients with MPM who were diagnosed at age ≤ 40 years. The mean PRS was significantly higher in MPM than in SPM and controls. Naevus count was comparable in early-onset MPM cases and those diagnosed at age > 40 years. CONCLUSIONS: Our cohort demonstrated higher frequencies of previously reported alleles associated with melanoma. MPM melanomas more commonly occur in UV-damaged areas, and these individuals are more likely to carry MC1R red hair colour alleles. Awareness of the interplay of genetic vulnerability with UV damage can stratify risk and guide recommendations for melanoma screening. What's already known about this topic? Skin phenotype, host genotype and ultraviolet (UV) damage all play a role in melanoma development. One of the main risk factors is a personal history of melanoma; second and subsequent primary melanomas account for over 20% of all melanomas registered in Queensland. Multiple loci are associated with melanoma risk, including many low-penetrance loci, which may have a cumulatively significant risk. Population-wide screening programmes for melanoma are not yet economically viable. What does this study add? Patients diagnosed with melanoma at age ≤ 40 years were more likely than older patients to have melanomas in non-UV-damaged sites. Patients with multiple melanomas had higher frequencies of MITF E318K, MC1R R-alleles, and the ASIP extended risk haplotype than patients with single melanoma. CDKN2A, MC1R and MTAP variants were more frequent in patients who developed melanomas at a younger age, but also in those whose melanomas were all on visibly UV-damaged sites. What is the translational message? Incorporating these genetic findings into the known risk factors of skin phenotype and visible UV damage may allow for a more customized and economically feasible approach to early detection of melanoma, particularly in younger patients. Plain language summary available online.

Level of contact hypersensitivity response to diphencyprone and keratinocyte cancer.

BACKGROUND: Keratinocyte cancers (KC) are common and pose a significant financial burden globally. Ultraviolet radiation is a significant factor in their development, through mutagenesis promotion but also through local and systemic immunosuppression. Although systemic immunosuppression is well understood, cutaneous immunity has been more difficult to evaluate. OBJECTIVES: This study used a contact sensitizer, diphencyprone (DPCP), which elicits a contact hypersensitivity reaction in skin, to compare the degree of reactivity to DPCP in patients with a high KC burden versus those with a low KC burden. METHODS: A prospective study was performed in immunocompetent patients aged 70 ± 5 years of age, comparing patients with a high KC burden (>10 previous KC) with those with a low KC burden (<2 previous KC). All patients were sensitized with 2% DPCP and then patch tested two weeks later with eight different concentrations of DPCP with the threshold concentration and total degree of reaction recorded. RESULTS: Nine patients were recruited, 5 in the 'high cancer' group and 4 in the 'low cancer' group. All patients were Fitzpatrick skin type 1 or 2. All patients developed a reaction to DPCP. Patients in the low cancer group developed a reaction at a significantly lower threshold DPCP concentration than the high cancer group (P = 0.039). The cumulative intensity of reaction was higher in the low cancer group (P = 0.087). CONCLUSION: Patients with a high KC burden required a higher threshold concentration of DPCP to elicit a hypersensitivity reaction, supporting the concept of a lower skin immunity in these patients. DPCP reactivity threshold could be a useful tool in the evaluation of skin immunity and propensity to develop keratinocyte cancers.

High naevus count and MC1R red hair alleles contribute synergistically to increased melanoma risk.

BACKGROUND: A high total body naevus count is the highest risk factor for melanoma; the phenotype of red hair colour, freckling and pale skin that burns easily, produced by MC1R R alleles, also predisposes to melanoma. OBJECTIVES: To determine whether the known melanoma risk factors of high naevus count and red hair or MC1R R alleles act synergistically to increase melanoma risk. METHODS: The Brisbane Naevus Morphology Study involved 1267 participants from volunteers presenting at a melanoma unit, dermatology outpatient clinic, private dermatology clinics, the Brisbane Longitudinal Twin Study and the QSkin Study. We examined pigmentation characteristics, total body naevus ≥ 5 mm count, and MC1R, ASIP and CDKN2A genotype in participants with and without a personal history of melanoma, living in Queensland, Australia, which is an area of high ultraviolet radiation. RESULTS: Cases were older than controls (median 57 vs. 33 years). Compared with individuals with dark brown hair and zero to four naevi, individuals with red hair and ≥ 20 naevi had a melanoma odds ratio of 10·0 (95% confidence interval 4·2-24·3). Individuals with MC1R R/R genotype and ≥ 20 naevi (≥ 5 mm diameter) had a melanoma odds ratio of 25·1 (95% confidence interval 8·4-82·7) compared with wild-type (WT)/WT individuals with zero to four naevi. The highest risk group is Australian men with the MC1R R/R genotype and ≥ 20 moles, who have an absolute risk of melanoma to age 75 years of 23·3%, compared with 0·8% for men with the WT/WT genotype and zero to four naevi. CONCLUSIONS: Patients who live in areas of high ultraviolet radiation, and have many large naevi and the red hair colour phenotype, particularly those with the MC1R R/R genotype, have a high risk of melanoma above the threshold recommended for screening in other cancers. Therefore, they should undergo intensive physician-led surveillance. What's already known about this topic? A high number of acquired melanocytic naevi, the red hair phenotype and MC1R R alleles all independently increase melanoma risk. Women with atypical naevi have an increasing melanoma risk gradient from darker hair to lighter hair. Women with many naevi have an increasing melanoma risk gradient from those with no elements of the red hair phenotype, to those with freckles but not red hair, to those with red hair. What does this study add? In Queensland, Australia, people with ≥ 20 naevi (≥ 5 mm diameter) and MC1R R/R genotype have a 25-fold increased melanoma risk, relative to people with zero to four naevi and the MC1R WT/WT genotype. In Queensland, individuals with ≥ 20 naevi and the MC1R R/R genotype have an absolute melanoma risk to age 75 years of 23·3% for men and 19·3% for women. This effect is independent of CDKN2A genotype. Further research is required to determine the effect of areas of lower ultraviolet radiation, as this study took place in the Queensland, Australia, which is an area of high ultraviolet radiation. MC1R R/r genotype is associated with increased total body naevus count but this is not the case for R/R. What is the translational message? Patients with many large naevi and the red hair colour phenotype, particularly those with an MC1R R/R genotype, have an unusually high risk of melanoma. In a high ultraviolet environment, this risk exceeds the threshold recommended for screening in other cancers, and such individuals should undergo intensive, regular, physician-led surveillance. Patients with many large naevi but with non-red colour hair may benefit further from clinical MC1R genotyping.

Phenotypic and genotypic analysis of amelanotic and hypomelanotic melanoma patients.

BACKGROUND: Amelanotic/hypomelanotic melanoma is associated with poorer outcomes due to a more advanced disease stage at diagnosis. OBJECTIVE: To determine phenotypic risks and genotypic associations with amelanotic/hypomelanotic melanoma to develop a clinical and genetic profile that could assist in identifying high-risk individuals. METHODS: The Brisbane Naevus Morphology Study conducted from 2009 to 2016 has recruited a core of 1254 participants. Participants were drawn from a combination of volunteers from dermatology outpatient clinics, private dermatology clinics, the Brisbane Longitudinal Twin Study and QSkin study. Case participants had a personal history of melanoma and control participants no personal history of melanoma. We specifically examined seven known candidate pigmentation and melanoma genes and pigmentary phenotypic characteristics in participants with amelanotic/hypomelanotic melanoma compared to pigmented melanomas. This assayed single nucleotide polymorphisms in MC1R, TYR, HERC/OCA2, IRF4, MTAP, PLA2G6 and MITF. RESULTS: Forty-seven participants had at least one amelanotic/hypomelanotic melanoma, and 389 had pigmented melanomas, with amelanotic/hypomelanotic melanoma patients significantly older than pigmented melanoma participants (63.3 ± 13.0 vs. 54.6 ± 15.3 years; P < 0.001). Amelanotic/hypomelanotic melanoma patients were more likely than pigmented melanoma patients to have red hair (34% vs. 15%; P = 0.01), severe hand freckling (13% vs. 5%; P = 0.01) and propensity to sunburn (63% vs. 44%; P = 0.01). MC1R R/R genotype was much more frequent in our amelanotic/hypomelanotic melanoma population (31.1% vs. 11%; P < 0.001; OR 26.4 vs. 5.9; control 1.0). Amelanotic/hypomelanotic melanoma was associated with TYR rs1126809*A/A [OR (CI 95%) 2.7 (1.1-6.8) vs. 1.2 (0.8-1.9)] and PLA2G6 rs11570734*A/A [OR (CI 95%) 3.7 (1.0-13.6) vs. 1.3 (0.9-2.0)]. The MTAP melanoma risk SNP genotype, associated with darker pigmentation, (rs4636294*A/A) was less common in amelanotic/hypomelanotic melanoma patients [OR (CI 95%) 0.8 (0.3-2.1) vs. 2.0 (1.3-3.1)]. CONCLUSIONS: Knowledge of phenotypic and genotypic associations of amelanotic/hypomelanotic melanoma can help predict risks and associations of this difficult to diagnose melanoma, which may ultimately assist clinical management and patient skin self-examination.