Basal cell carcinoma - clinical review

Basal cell carcinoma (BCC) is the most common skin cancer in humans.(1)

Classic BCC highlighted in white; less obvious BCC highlighted in black
Classic BCC highlighted in white; less obvious BCC highlighted in black

Section 1: Epidemiology and aetiology

BCC is a slow-growing, locally invasive, non-melanoma skin cancer (NMSC) that rarely metastasises.

Left untreated, BCC can cause significant morbidity, infiltrating underlying cartilage, muscle and bone.

BCCs arise most frequently on sun-exposed areas of the head and neck, although any cutaneous hair-bearing surface can be affected.

White males are the highest-risk group for the development of BCC, with other major risk factors including advancing years, genetic susceptibility, cumulative UV exposure, immunosuppression and previous diagnosis of BCC.

The highest incidence rates in the world are in Australia, with an estimated 296,000 BCCs diagnosed in 2008. However, as in the UK, reporting of NMSC in Australia is not compulsory, so this figure is likely to be much higher. In 2010, as many as 247,000 BCCs may have been treated surgically in the UK.2 This would make the incidence of BCC almost as high as that of all other cancers combined. This figure is predicted to rise as the population ages and sun-seeking behaviour continues.

Classification

BCCs can be classified by their clinical and histopathological appearance, and risk stratified depending on the location where they have arisen.

The major variants of BCC are superficial, nodular, morphoeic (sclerosing) and pigmented.

Nodular BCCs are the most commonly presenting lesion and are more likely to arise on the head and neck, whereas superficial BCCs are often found on the trunk and limbs.3

Interestingly, the exact cellular origin of BCC is still unknown. Classically they are thought to arise from the epidermal basal cell layer, although current theory supports either a follicular or interfollicular stem cell origin.4

Elucidation of the exact mechanism by which BCCs arise is a focus of current research.

Section 2: Making the diagnosis

In many cases, BCC can be diagnosed clinically. A careful history is useful to determine the duration of growth, as well as to determine risk factors.

Be aware that patients may report only having had a lesion for a few weeks, especially if it has arisen in a difficult to observe area, such as behind the ear or on the back.

Examination, measurement
Examining and measuring the lesion is imperative. Palpate the area to assess depth, and stretch the surrounding skin to look for surface irregularities.

This can often reveal the characteristic pearly appearance of a nodular, morphoeic or even superficial BCC. It can also help to unmask a nodular BCC with a morphoeic component that can extend further than originally noted.

If surface crust is obscuring the lesion, and the patient is amenable, removal using gauze soaked with sterile saline can be informative.

Clinical features
The following subtypes of BCC may be seen:

  • Superficial BCC Often misdiagnosed as dry skin, eczema or psoriasis. Slow growing and usually well demarcated, they may be single or multiple and irregular in shape and size. Suspect any flat, scaly, erythematous lesion on the trunk or limbs that has failed to respond to emollients or topical steroids.
  • Nodular BCC A solitary, shiny, pinkish-red papule or nodule. Centre may be cratered and/or crusted, with the edges exhibiting a pearlescent 'rolled' appearance. Tumours tend to demonstrate 'arborising' (branch-like) blood vessels that may only be visible with magnification or a dermatoscope.
  • Morphoeic or sclerosing BCC Flat or slightly raised, pale and, as the name suggests, scar-like. This type tends to be more locally infiltrative than nodular BCC, is more prone to recur and often requires larger surgical margins.
  • Pigmented BCC Demonstrates the features of a nodular BCC as well as shades of blue, black or grey. Can be mistaken for malignant melanoma, and any diagnostic doubt should prompt urgent referral.

BCCs are often asymptomatic, but can be sore or itchy. If ulcerated, they may bleed with minimal trauma. Some patients, especially the elderly, present late with large, symptomatic, crusted lesions, only seeking help when the area involved becomes troublesome.

Ulcerated or crusted lesions can become inflamed and superficially infected. In these cases, a skin swab and antimicrobial therapy can be helpful pending definitive management of the lesion. Skin biopsy may be required for BCCs at sites of high risk for recurrence, because this may influence clinical management.

Section 3: Managing the condition

Complete tumour removal providing an acceptable cosmetic result is the primary aim of treating BCC.

Current treatments
Treatments are broadly divided into two categories:

  • Surgical treatments Surgical excision, curettage and cautery, cryosurgery and Mohs micrographic surgery (MMS).
  • Non-surgical treatments 5-fluorouracil cream, imiquimod cream, photodynamic therapy and radiotherapy.

Low-risk (as defined by NICE) superficial and nodular BCCs can be managed with surgical excision with a predetermined peripheral margin of 4-5mm. This will result in a 95% complete excision rate.5

Curettage and cautery can be useful for small, low-risk nodular or superficial BCCs. The technique provides histology (although no information regarding margins). Cosmetic results and cure rates are variable, depending on operator experience.

Cryotherapy is useful for treating small, low-risk lesions, including superficial BCCs. No histology is obtained and it is vital for the operator to be certain of the clinical diagnosis.


Dermoscopic image of a BCC shows characteristic branching vessels

Scarring, infection and blistering are common side-effects. Cure rates vary widely, depending on operator skill and lesion selection.

Non-surgical treatments are attractive in small, low-risk superficial BCCs, but follow-up is often required to determine treatment success.

If non-surgical treatment is planned, twoto three-month follow-up to assess clinical resolution is a sensible course of action.

If surgery is performed and histological margins are suitably clear, follow-up may be unnecessary.

New developments
Although surgery remains the mainstay of treatment for most types of BCC, new developments include hedgehog signalling pathway inhibitors such as vismodegib, which gained US Food and Drug Administration approval in January 2012 for metastatic or advanced, inoperable BCC.

Guidelines
NICE states that low-risk BCCs may be treated in primary care, for which two algorithms exist. GPSIs are permitted to excise a broader range of low-risk BCCs. The full NICE guidelines provide further clarification, but to summarise:

  • All BCCs at sites of high risk for recurrence should be referred to secondary care.
  • Superficial BCCs should only be treated non-surgically by GPs with knowledge and experience of available medical treatments.
  • Low-risk, nodular BCCs in non-immunosuppressed patients over 24 years of age may be treated surgically.

Low-risk BCC is defined as:

  • Not on the head or neck.
  • Less than 1cm in diameter (with well-defined margins) and must not be recurrent, morphoeic, infiltrative or basosquamous.
  • Not located in an area difficult to close surgically, not overlying important structures and not in a highly visible area of cosmetic importance to the patient.

All BCCs that fall outside these criteria should be referred to the local hospital skin cancer multidisciplinary team.

Section 4: Prognosis

BCCs are slow-growing tumours that are almost always restricted to the skin.

With appropriate treatment, the prognosis is excellent and patients can often be reassured.

The main concern in patients with BCC is local recurrence due to incomplete excision or non-surgical treatment failure.

Patients who develop a BCC are also at a higher risk of developing a further BCC than the general population.

It is important to educate these patients about self-examination of the skin and to recommend seeking medical advice regarding any lesion causing concern, especially if there is a history of change.

Section 5: Case study

A 65-year-old man presented with a two-year history of a slow-growing 'spot' on the right temple.

He had previously had multiple actinic keratoses on his scalp, which had been treated with 5-fluorouracil cream three years ago.

The area on the right temple had become slightly sore over the past two months. He decided to seek medical advice, wanting to know if he could use 5-fluorouracil cream.

He took early retirement in his 50s and spends six months a year in Portugal with his wife.

On examination, he had a raised papular lesion measuring 8 x 6mm on the right temple. Gently stretching the lesion revealed a shiny pearlescent rim with a subtle extension posteriorly beyond the obvious boundaries of the papule.

A clinical diagnosis of mixed nodular BCC with a possible morphoeic component was made and he was referred to secondary care.

A 4mm skin biopsy was confirmatory and histology revealed an infiltrative growth pattern.

The patient chose to proceed with MMS and the BCC was removed under local anaesthetic with advancement flap closure. Sutures were removed one week postoperatively. The patient was reassured and given advice on photoprotection and skin self-examination.

Discussion
BCCs can often be diagnosed clinically, so biopsy is not always necessary unless clarification of the subtype will affect management.

BCCs on the head and neck are considered high risk for recurrence, especially if they have a morphoeic component. In this case, MMS is useful. In this tissue-sparing procedure, the visible tumour is excised with (usually) 2mm margins and examined histologically by the surgeon while the patient waits. If the margins are involved, more tissue is removed until the tumour is fully excised. The defect is then repaired.

(top) An ill-defined morphoeic BCC on the nose (highlighted in white). This example of a high-risk lesion was treated using MMS.

(bottom) Post MMS defect with tumour free margins. It is important to note that the tumour extends beyond clinical margins in an asymmetric fashion, and this technique minimises removal of normal skin at important sites.

Section 6: Evidence base

Review

  • Bath-Hextall FJ, Perkins W, Bong J et al. Interventions for basal cell carcinoma of the skin. Cochrane Database Syst Rev 2007; 1: CD003412.

This Cochrane review concluded that 'there is very little good quality research on the various treatment modalities for BCC'. Although surgery appears to be the best overall treatment, there is a need for more comparative RCTs.

Guidelines

This updated guidance is particularly relevant for GPs treating BCCs in the community.

Online

  • British Association of Dermatologists' evidence-based guidelines for the management of BCC.

References

1. Bath-Hextall FJ, Perkins W, Bong J et al. Cochrane Database Syst Rev 2007; 1: CD003412.

2. Levell NJ, Igali L, Wright KA et al. Clin Exp Dermatol 2013; 38(4): 367-9.

3. Ceilley RI, Del Rosso JQ. Int J Dermatol 2006; 45(5): 489-98.

4. Sellheyer K. Br J Dermatol 2011; 164(4): 696-711.

5. Telfer NR, Colver GB, Morton CA. Br J Dermatol 2008; 159: 35-48.

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  • Contributed by Dr David Brass, specialist trainee in dermatology, and Dr Neil Rajan, senior lecturer and honorary consultant dermatologist, Royal Victoria Infirmary, Newcastle upon Tyne.
CPD IMPACT: EARN MORE CREDITS

These further action points may allow you to earn more credits by increasing the time spent and the impact achieved.

  • Review protocols for undertaking BCC removal in primary care. Produce a written protocol based on your review.
  • Consider buying a dermatoscope and learn how to use it with guidance from a dermatologist.
  • Produce public health information posters on sun safety and use them for opportunistic health promotion.

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