Symptoms and Signs
The commonest subtype of melanoma is known as superficial spreading melanoma: this classically presents as a pigmented skin lesion (‘mole’) that has changed in size, shape or colour  (Fig. 3). It most commonly presents on the trunk in men and on the legs in women . Other melanoma subtypes include nodular melanoma (5%), lentigo maligna (melanoma in situ, 4–15%), and acral lentiginous melanoma (5%) [36, 37] and these may present in different ways.
Nodular melanomas tend to occur on the head and neck of older people: they grow quickly, and are usually firm, symmetrical and evenly pigmented papules or nodules, which may ulcerate and bleed.
Lentigo maligna (also known as Hutchinson’s freckle) develop as a slow-growing precursor pigmented macule which may remain in situ for many years. Once it becomes invasive it is known as lentigo maligna melanoma and may progress rapidly, often being poorly defined and variably pigmented; they are much more common in people aged 60 and over.
Acral lentiginous melanomas occur exclusively on the palms and soles and under nails, and are thought to be unrelated to sun exposure. Although uncommon among Caucasians, they are commoner in people with pigmented or Asian skin. They typically appear as a large pigmented macule, but can mimic warts with a verrucous, non-pigmented appearance [38,39,40].
An estimated 2–20% of melanomas are amelanotic—these can appear as a non-pigmented mimic of any subtype, with nodular melanomas the most likely to be amelanotic . They are more common in older age groups over 70 years of age and in the head and neck region, and tend to have worse outcomes than pigmented melanomas .
NICE guidance (2015) recommends using naked eye examination and the weighted Glasgow 7-point checklist to assess suspicious skin lesions (see Fig. 4; [24, 41, 42]). If a lesion scores 3 or more, then referral via an urgent suspected cancer pathway is recommended . There are a number of other checklists available, such as the “ABCDE” mnemonic, most commonly used in North America, which refers to Asymmetry, Border irregularity, Colour variation, Diameter larger than 6 mm, Evolution/changing [43, 44]. NICE recommends that a suspected melanoma should not be excised in primary care , although a recent study suggests that no harm came to patients undergoing primary care excision in the rural Scottish setting . To avoid missing atypical melanomas, the NICE clinical knowledge summary also recommends referring the following lesions via an urgent suspected cancer pathway: new nodules which are pigmented or vascular in appearance; nail change such as a new pigmented line or pigmentation under the nail; or any skin lesion that is persistent or slowly evolving and unresponsive, with an uncertain diagnosis .
A routine referral for risk estimation, education and possible surveillance should be considered for anyone who is potentially at high risk for developing melanoma. This includes those who have giant congenital pigmented naevi (benign melanocytic naevi originating in utero measuring greater than 20 cm in diameter ), a family history of three or more melanoma cases, more than 100 normal moles, or any atypical moles (particularly if multiple) .
Squamous Cell Carcinoma (SCC)
Symptoms and Signs
SCCs tend to arise in areas that are frequently exposed to the sun: face, scalp, ears, neck, and upper limbs  (Fig. 5). Typically, they appear either as an indurated (firm), nodular, crusted lesion, or as an ulcer with no crusting [49, 50]. However, their appearance is variable and they should be suspected in any lesion that is larger than 1 cm, is non-healing, keratinized or crusted, and has a documented expansion over the past 8 weeks . In situ SCC (Bowen’s disease) typically appear as erythematous, scaly plaques with clearly defined margins, but can sometimes be pigmented and flat with poorly defined margins . A variant of SCC is keratoacanthoma; these are domed, fast-growing, nodules with a central hyperkeratotic region . High-risk SCCs include those on the lips, ears, non-sun-exposed sites, in areas of previous injury, those that are larger than 2 cm in diameter, are in immunocompromised patients, or are a recurrence of a previously treated lesion. These have a higher probability of metastasis and recurrence after treatment .
As for melanoma, confirmation of an SCC relies on excision and histopathological examination; therefore all patients with a suspicious lesion should be referred on an urgent suspected cancer pathway to secondary care .
Basal Cell Carcinoma (BCC)
Symptoms and Signs
BCCs commonly arise in the head, neck, trunk and limbs , but can be variable in their clinical presentations (Fig. 6). There are several histological subtypes  which may present differently. Nodular and micro-nodular BCCs are commonly found on the face and present as pearly pink or white cystic papules or nodules that have telangiectasia on their surface and may be ulcerated. Superficial BCCs are usually on the upper trunk and shoulders, and present as erythematous, well-demarked, scaly plaques with pearly white borders. They are often large (> 20 mm), multiple and slow growing, and can be confused with Bowen’s disease. Another important mimic is amelanotic melanoma, which can present as a red lesion and be confused with a BCC . Morphoeic BCCs (also known as sclerosing or infiltrative) usually occur on the face and present as skin-coloured, waxy, scar-like lesions; they tend to recur and can infiltrate cutaneous nerves. Pigmented BCCs are brown, blue or greyish lesions that can resemble melanomas. Baso squamous BCCs have mixed BCC and SCC characteristics and can be more aggressive than other forms of BCC [53, 55, 56].
The 2010 NICE guidance recommends that low-risk BCCs (see Fig. 7) may be excised by primary care clinicians with appropriate training [53, 57]. This guidance may vary by local agreement, depending on the clinicians’ role, competencies and local policy. For all other patients with a suspected BCC, routine referral to specialist care is recommended, although, if there is concern that a delay in referral will make a “significant impact” because of factors such as lesion site or size, then referral via an urgent cancer pathway should be considered .
Tools for Evaluating Suspicious Skin Lesions in Primary Care
A dermatoscope is a handheld magnification tool and light source which eliminates skin surface reflection, and can help assessment of skin lesions with visualisation of deeper subsurface structures . Dermoscopy performed by trained specialists is both more sensitive and specific in classifying skin lesions than clinical examination with the naked eye alone [59, 60]. There have been two recent Cochrane reviews of the evidence for dermoscopy to diagnose keratinocyte carcinomas  and melanoma . Both found that most evidence was derived from secondary care populations; hence, there was insufficient evidence to support routine use of dermoscopy by primary care clinicians. Our group’s recent systematic review of dermoscopy use in primary care also found the literature to be scanty; however, there was some evidence that dermoscopy has the potential to help primary care clinicians triage suspicious lesions . It also highlighted that further evidence is needed on patient acceptability and minimum training requirements for primary care clinicians to reach competence, as well as the cost-effectiveness of implementing dermoscopy in primary care.
This term describes the use of information technology to facilitate skin management, most commonly by sharing digital images of lesions with dermatology specialists. Teledermatology referral systems are already well established in some areas of the UK. A recent Cochrane review assessing the diagnostic accuracy of teledermatology for detecting melanomas, BCCs and SCCs in adults compared to face-to-face diagnosis by a specialist concluded that teledermatology is accurate for identifying the majority of malignant lesions . However, it also suggested that further research is needed to fully determine its diagnostic accuracy, feasibility and cost-effectiveness as a triaging tool for referring suspicious skin lesions from primary to secondary care.
Spectrophotometric intracutaneous analysis (SIAscopy) is a non-invasive scanning technology, incorporated into the MoleMate system, and evaluated in a randomised controlled trial set in UK general practice. The MoleMate system was not found to improve appropriateness of referral, and its use led to a higher proportion of lesions being referred . However, there was some evidence that a higher referral rate from general practice may actually be cost-effective owing to improved outcomes associated with earlier diagnosis of melanomas .
Artificial Intelligence (AI)-Supported Systems
The use of AI/machine learning to evaluate skin lesions has received a huge amount of recent attention in both the lay and medical press. Experimental studies using images of lesions from specialist clinics have shown that AI algorithms can classify images of skin cancer with an accuracy that matches or even exceeds dermatologists [67, 68]. This suggests that AI has the potential to assist primary care clinicians to triage suspicious skin lesions; research is now needed on real-world primary care populations to establish the accuracy and safety of using these AI technologies in primary care.
Other Diagnostic Tools
Many other non-invasive tests and diagnostic technologies have been developed to aid skin cancer diagnosis, including high frequency ultrasonography, optical coherence tomography, reflectance confocal microscopy, and computer-assisted diagnosis. They have been evaluated in several recent Cochrane reviews, all of which found a paucity of evidence for their accuracy in either primary or specialist care settings. Therefore, at present, there is insufficient evidence to recommend their use [64, 69,70,71,72,73].