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Cochrane Special Collections

Diagnosing skin cancer

22 May 2020
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Special Collection

Accurate detection of all skin cancer types is essential for its appropriate management, reduction of morbidity, and improvement in survival rates. There are three main forms of skin cancer. Melanoma and cutaneous squamous cell carcinoma (cSCC), are high-risk skin cancers with the potential to metastasise, and ultimately lead to death. A basal cell carcinoma (BCC) rarely metastasises, usually remaining localised with potential to infiltrate and damage surrounding tissue. BCCs and cSCCs are also referred to as keratinocyte skin cancers.

The aim of any testing for skin cancer is to detect all possibly malignant cases using high sensitivity techniques, without having too many false positives, which lead to unnecessary referrals. There is a trade-off between sensitivity and specificity, as techniques with high sensitivity lead to lower specificity (a higher number of false positives). With increasing rates of skin cancer worldwide [1, 2], and a trend to adopt dermoscopy, and other high-resolution image analysis in primary care, anxiety around missing identification of early malignant lesions needs to be balanced against the risk of unnecessary referrals to specialists. 
If additional testing is used in primary care to make sure that potentially malignant lesions are detected, there is a risk that the number of people with benign skin conditions who are referred unnecessarily to specialist care will increase. It is important, therefore, that tests should be evaluated in the settings in which they will be used in practice. Sophisticated techniques from specialist settings, need to be assessed in terms of their ability to diagnose more difficult cases, and whether they can reduce unnecessary excisions.

Screening is the systematic investigation of individuals who are not known to have the disease or condition screened for. With screening, there is a risk of overdiagnosis of lesions which would not have caused any problems to the individual. Overdiagnosis has been well documented when screening for other cancers like prostate and breast cancer. Overdiagnosis leads to unnecessary, often invasive treatment with negative physical and psychological consequences. A cancer diagnosis itself can seriously affect quality of life for the affected person and their relatives.

The Cochrane Reviews in this Special Collection focus on diagnosis of cutaneous melanoma, keratinocyte skin cancer and all types of skin cancer. This collection brings together a series of screening and diagnostic test accuracy systematic reviews for diagnosing skin cancer, which aim to identify the most accurate approaches to diagnosis, and so provide the best evidence on which clinical and policy-related decisions can be based.  The reviews have been conducted by the Cochrane Skin Group. They have been led by Dr Jac Dinnes, and funded by the UK National Institute for Health Research

Diagnosis of cutaneous melanoma

Visual inspection for diagnosing cutaneous melanoma in adults

History-taking and visual inspection of a suspicious lesion by a clinician is usually the first in a series of tests to diagnose skin cancer. This review aims to determine the diagnostic accuracy of visual inspection for the detection of cutaneous invasive melanoma and intraepidermal melanocytic variants in adults with limited prior testing, and in those referred for further evaluation of a suspicious lesion.

Dermoscopy, with and without visual inspection, for diagnosing melanoma in adults

Dermoscopy is a magnification technique that uses visible light and allows a more detailed examination of the skin than is possible by the naked eye alone. This review aims to determine the diagnostic accuracy of dermoscopy for the detection of cutaneous invasive melanoma and atypical intraepidermal melanocytic variants in adults, and to compare its accuracy with that of visual inspection alone.

Reflectance confocal microscopy for diagnosing cutaneous melanoma in adults

Reflectance confocal microscopy (RCM) is a microscopic technique that uses infrared light to visualise deeper layers of the skin than can be seen with dermoscopy. Used by a specialist clinician in conjunction with clinical or dermoscopic suspicion of malignancy, or both, RCM may reduce unnecessary excisions without missing melanoma cases. This review aims to assess the diagnostic accuracy of RCM for the detection of cutaneous invasive melanoma and atypical variants in adults with any lesion that may be suspected of being melanoma and difficult to diagnose lesions, and to compare its accuracy with that of dermoscopy.

Smartphone applications for triaging adults with skin lesions that are suspicious for melanoma

Smartphone applications are readily accessible and potentially offer an instant risk assessment of the likelihood of malignancy in skin lesions, that would enable patients to seek further medical attention from a clinician for more detailed assessment. There is a risk that melanomas will be missed, and treatment delayed if the application reassures the user that their lesion is low-risk. This review assesses the diagnostic accuracy of smartphone applications to rule out cutaneous invasive melanoma and intraepidermal melanocytic variants in adults with concerns about suspicious skin lesions.

Diagnosis of keratinocyte skin cancer - basal cell carcinoma (BCC) and cutaneous squamous cell carcinoma (cSCC)

Visual inspection and dermoscopy, alone or in combination, for diagnosing keratinocyte skin cancers in adults

Establishing the value of dermoscopy over and above visual inspection for the diagnosis of BCC or cSCC in primary- and secondary-care settings is critical to understanding its potential contribution to appropriate skin cancer triage, including referral of higher-risk cancers to secondary care, the identification of low-risk skin cancers that might be treated in primary care, and to provide reassurance to those with benign skin lesions who can be safely discharged. This review aims to determine the diagnostic accuracy of visual inspection and dermoscopy, alone or in combination, for the detection of BCC and cSCC. 

Reflectance confocal microscopy for diagnosing keratinocyte skin cancers in adults

Reflectance confocal microscopy (RCM) may help to identify cancers that are eligible for non-surgical treatment without the need for a diagnostic biopsy, particularly in people with suspected BCC. This review determines the diagnostic accuracy of RCM for the detection of BCC, cSCC, or any skin cancer in adults with any suspicious lesion and lesions that are difficult to diagnose. 

Exfoliative cytology for diagnosing basal cell carcinoma and other skin cancers in adults

Exfoliative cytology is a non-invasive test that uses the Tzanck smear technique to identify disease by examining the structure of cells obtained from scraped samples. It is a less invasive diagnostic test than skin biopsy, and for BCC, it has the potential to provide an immediate diagnosis that avoids an additional clinic visit to receive skin biopsy results. This review aims to determine the diagnostic accuracy of exfoliative cytology for detecting BCC in adults. 

Screening and diagnosis of skin cancers including melanoma, BCC and cSCC

Teledermatology for diagnosing skin cancer in adults

Teledermatology enables generalist clinicians to access the opinion of a specialist dermatologist for suspicious skin lesions remotely, without referring patients through the normal referral pathway. Consultations can be 'store-and-forward' with electronic digital images of lesions sent to a dermatologist for review, or interactive consultations using videoconferencing to connect the patient, referrer, and dermatologist in real time. This review determines the diagnostic accuracy of teledermatology for the detection of any skin cancer (melanoma, BCC or cSCC) in adults, and to compare its accuracy with that of in-person diagnosis.

Computer‐assisted diagnosis techniques (dermoscopy and spectroscopy‐based) for diagnosing skin cancer in adults

Computer-assisted diagnosis (CAD) systems use artificial intelligence to analyse lesion data and diagnose when skin cancer is present. CAD may reduce unnecessary excisions without missing melanoma cases. This review aims to determine the accuracy of CAD systems for diagnosing cutaneous invasive melanoma and atypical intra-epidermal melanocytic variants, BCC or cSCC in adults, and to compare its accuracy with that of dermoscopy.

High‐frequency ultrasound for diagnosing skin cancer in adults

Ultrasound is a non-invasive imaging technique that measures sound wave reflections from the tissues of the body. At lower frequencies, the deeper structures of the body, such as the internal organs, can be visualised, while high frequency ultrasound (HFUS) has a much lower depth of tissue penetration, but produces a higher resolution image of tissues and structures closer to the skin surface. When used in conjunction with clinical or dermoscopic examination (or both) of suspected skin cancer, HFUS may offer additional diagnostic information compared to other technologies. This review aims to assess the diagnostic accuracy of HFUS for the detection of cutaneous invasive melanoma and atypical intraepidermal melanocytic variants, BCC, or cSCC in adults.

Optical coherence tomography for diagnosing skin cancer in adults

Optical coherence tomography (OCT) is a non–invasive technology based on the same principle as ultrasound, which measures the optical scattering of near–infrared light waves from under the surface of the skin. When used in conjunction with clinical or dermoscopic examination (or both) of suspected skin cancer, OCT may offer additional diagnostic information compared to other technologies. This review aims to assess the diagnostic accuracy of OCT for the detection of cutaneous invasive melanoma and atypical intraepidermal melanocytic variants, BCC, or cSCC in adults.

Screening for reducing morbidity and mortality in malignant melanoma

Screening for malignant melanoma has the potential to reduce morbidity and mortality from the disease through earlier detection, as prognosis is closely associated with the thickness of the lesion at the time of diagnosis. However, there are also potential harms from screening people without skin lesion concerns, such as overdiagnosis of lesions that would never have caused symptoms if they had remained undetected. Overdiagnosis results in harm through unnecessary treatment and the psychosocial consequences of being labelled with a cancer diagnosis. For any type of screening, the benefits must outweigh the harms, and this must be demonstrated in high-quality randomised trials. Screening for malignant melanoma is currently practised in many countries, and the incidence of the disease is rising sharply, while mortality remains largely unchanged. This review assesses the effects on morbidity and mortality of screening for malignant melanoma in the general population.

About this Special Collection

References

Ferlay J, Soerjomataram I, Dikshit R, Eser S, Mathers C, Rebelo M, et al. Cancer incidence and mortality worldwide: Sources, methods and major patterns in GLOBOCAN 2012. International Journal of Cancer 2015;136(5): E359-86. [PubMed: 25220842]

Lomas A, Leonardi-Bee J, Bath-Hextall F. A systematic review of worldwide incidence of nonmelanoma skin cancer. British Journal of Dermatology 2012;166(5):1069-80. [PubMed: 22251204]

Acknowledgements

This Special Collection was first published in December 2018, and updated in May 2020. It was developed by the Cochrane Editorial & Methods Department, in collaboration with Dr Jac Dinnes (Institute of Applied Health Research, University of Birmingham) of the Cochrane Skin Group, who wrote the introduction. It contains reviews by the Cochrane Skin Group. Karsten Juhl Jørgensen (Cochrane Nordic Centre) contributed to the May, 2020 update. The project was supported by the National Institute for Health Research, via Cochrane Infrastructure funding to the Cochrane Skin Group and Cochrane Programme Grant funding. The views and opinions expressed therein are those of the authors and do not necessarily reflect those of the Systematic Reviews Programme, NIHR, NHS or Department of Health.

Image credit

Amelie-Benoist/ BSIP / Science Photo Library

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Cochrane Editorial and Methods ([email protected])

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