Basal Cell Carcinoma (Rodent Ulcer)

Basal cell carcinomas (BCCs) are slow-growing, locally invasive malignant epidermal skin tumours which are thought to arise from hair follicles. BCCs predominantly affect Caucasians.

The tumour infiltrates local tissues through the slow irregular growth of subclinical finger-like outgrowths but metastases are extremely rare and morbidity results from local tissue invasion and destruction, especially on areas of chronic sun exposure such as the face, head and neck.¹

There are a number of different types of basal cell carcinoma, including:

• Nodular or cystic: solitary, shiny, red nodule with large telangiectatic vessels. Often occur on the face.
• Superficial: tend to occur on the trunk and are very slow growing. Often flat, well demarcated erythematous plaques. Can appear similar to psoriasis, discoid eczema and Bowen's disease.
• Morphoeic: more aggressive and have poorly defined borders. Often present late and may become very large and then require extensive plastic surgical reconstruction.
• Pigmented: nodular with increased brown or black pigment; are seen more often in individuals with dark skin.²

• BCC is the most common cancer in Europe, Australia and the USA and is showing a worldwide increase in incidence.¹
• 60% of all skin cancers are BCCs and the incidence is increasing each year.
• The age standardised incidence of basal cell carcinoma in south Wales was estimated at 114.2 per 100 000 population in 1998.³
• The estimated lifetime risk of basal cell carcinoma in the white population is 33-39% in men and 23-28% in women.
• Basal cell carcinoma is very uncommon in dark skinned races.

Risk factors¹

• The most significant aetiological factors appear to be genetic predisposition and exposure to ultraviolet radiation.
• The sun-exposed areas of the head and neck are the most commonly involved sites.
• Sun exposure in childhood may be especially important.
• Increasing age, male sex, skin types I and II (skin that always burns and never/only sometimes tans), immunosuppression and arsenic exposure are other recognised risk factors. A high dietary fat intake may also be relevant.
• Multiple BCCs are a feature of basal cell naevus (Gorlin’s) syndrome (BCNS):
  • Autosomal dominant inheritance
  • Multiple basal cell carcinomas
  • Pitting of the palms and soles
  • Jaw cysts
  • Spine and rib anomalies
  • Calcification of the falx cerebri
  • Cataracts
• Other conditions associated with an increased risk of basal cell carcinoma include xeroderma pigmentosa and albinism.

• The sun-exposed areas of the head and neck are the most commonly involved sites.¹ Approximately 80% occur on the head and neck, with the rest mainly on the trunk and lower limbs.
• Early lesions are often small, translucent or pearly and have raised areas with telangiectasia.
• The classic rodent ulcer has an indurated edge and ulcerated centre. It is slow growing but can spread deeply to cause considerable destruction.

It is important to distinguish between high and low risk BCCs, based on their likelihood of recurrence after treatment. Factors indicating higher risk include:

• Histological sub-type:
  • Morphoeic: linear groups of cancer cells with surrounding scarring; clinically this causes a thickened and hardened skin
  • Infiltrating: like morphoeic but with less scarring
  • Micronodular: very small groups of cancer cells
  • Basosquamous carcinoma: both basal and squamous elements
• Histological features:
  • Perineural invasion
  • Invasion below dermis
• Sites:
  • Nose and paranasal folds
  • Periocular
  • Ears
  • Scalp and temples
  • Lips
• Other factors:
  • Size > 2 cm
  • Immunosuppression
  • Genetic disorders such as Gorlin’s syndrome
  • Previously treated lesion

• Nodular basal cell carcinoma:
  • Intradermal nevus
  • Sebaceous hyperplasia
  • Fibrous papule
  • Molluscum contagiosum
  • Keratoacanthoma
• Superficial basal cell carcinoma:
  • Discoid eczema
  • Psoriasis
  • Actinic keratosis (solar keratosis)
  • Bowen's disease
  • Squamous cell carcinoma
  • Seborrhoeic keratosis
• Pigmented basal cell carcinoma:
  • Melanoma
• Morphoeic basal cell carcinoma:
  • Scar tissue
  • Localised scleroderma

• Investigation is primarily by visual inspection and removal for histology where necessary.⁴
• All excised specimens should be sent for histopathological examination.
• When non-surgical treatments are used, an incisional biopsy must be sent before treatment for confirmation of the diagnosis.
• Biopsy is also indicated when clinical doubt exists or when the histological subtype of BCC may influence treatment selection and prognosis.¹
• For most patients with non melanoma skin cancer (NMSC) no formal staging beyond clinical examination for lymphadenopathy is required.⁴
• CT or MRI scan are indicated in cases where bony involvement is suspected or where the tumour may have invaded major nerves, the orbit or the parotid gland.¹

• Refer a patient presenting with skin lesions suggestive of skin cancer or in whom a biopsy has confirmed skin cancer to a team specialising in skin cancer.
• Refer patients with persistent or slowly evolving unresponsive skin conditions with uncertain diagnosis to a dermatologist.
• Basal cell carcinomas are slow growing and can be referred non-urgently.

• There should be two levels of multidisciplinary teams: local hospital skin cancer multidisciplinary teams (LSMDTs) and specialist skin cancer multidisciplinary teams (SSMDTs).
• Patients with low-risk basal cell carcinomas should be diagnosed, treated and followed up by doctors working in the community as part of the LSMDT/SSMDT - usually a GP with a special interest in dermatology (GPwSI) - or a local hospital skin cancer specialist, normally a dermatologist, who is a member of the LSMDT/SSMDT.
• Patients with high-risk BCCs and where there is doubt about the lesion being low or high grade should be referred directly to the LSMDT/SSMDT.
• Patients with BCC should be seen by the relevant specialist within 2 months of receipt of referral by their GP and be subsequently treated within a further 3 months.
• Patients with a high risk of recurrence of skin cancer or of new primary cancers should normally be followed up in hospital but should still be instructed in self examination and provided with written and photographic information.

Management options⁴

Surgery and radiotherapy appear to be the most effective treatments with surgery showing the lowest failure rates. There is only limited evidence of the effectiveness of other treatment modalities compared to surgery.^6,7 Recurrent BCC is more difficult to cure than primary lesions.¹

• Surgical:
  • Excision with primary closure, flaps and grafts: an excision margin of 4 mm around the tumour is recommended where possible, especially for all high risk BCCs.³
  • Mohs micrographic surgery:
    • Excision of the BCC is carried out in stages and each stage checked histologically.
    • It is advocated for use in cases where it is critical to obtain a clear margin while preserving the maximum amount of normal surrounding tissue, especially for recurrent and high-risk aggressive growth pattern BCCs such as morphoeic BCCs.
    • Morphoeic and recurrent tumours are best treated by Mohs' micrographic surgery where this is available.³
    • Overall cure rates for primary BCC are almost 100% and 95% for recurrent BCC.²
    • The main problems are the length of the procedure, the need for special equipment and training, the relatively high cost and the limited availability in the UK.
  • Curettage and cautery/electrodesiccation:
    • Not recommended for recurrent, large, morphoeic tumours or tumours on the face.
    • The overall cure rate is over 90% for low-risk BCCs.
    • Performed using a curette to remove soft material from the tumour.
    • The base of the tumour is then destroyed, using either hyfrecation or cautery.
    • This may be used to treat small (less than 1 cm) primary BCCs.
    • It is safe and well tolerated, and usually produces a good cosmetic outcome. It is suitable for patients with multiple lesions.
    • The histology may be difficult to interpret as the lesion may be incompletely removed and margins of excision cannot be assessed optimally.
  • Cryotherapy/cryosurgery:
    • Cryotherapy is well established for treating small low-risk lesions including superficial BCCs. Histology is not available unless an incisional biopsy is taken first.
• Non-surgical:
  • Topical treatment:
    • Imiquimod 5% cream:
      • Is an immune-response-modifying agent that has recently been licensed for the treatment of small superficial BCCs.
      • Imiquimod has been shown to achieve clearance rates ranging from 70% to 100% but relapse rates appear higher than with other, conventional treatments and there are some difficulties with side-effects (e.g. pruritus).⁸
      • More effective for superficial than nodular tumours.²
    • Topical fluorouracil 5% cream is useful in the management of multiple superficial basal cell carcinoma on the trunk and limbs. Cure rates are in the region of 80%.
  • Photodynamic therapy (PDT):
    • Involves the use of light therapy in combination with a topical photosensitising agent to destroy cancer cells.
    • Its use has been well described in the treatment of superficial BCC. Evidence of efficacy is adequate to support its use.⁹
    • The average clearance rate for superficial basal cell carcinoma is about 85% but is lower in nodular basal cell carcinoma.³
    • Advantages of PDT include a low rate of adverse effects and good cosmetic outcome.
    • The disadvantages are that the patient has to be available for a period of at least 3–4 hours for treatment, and that the photosensitiser and equipment are relatively expensive.
    • There is currently little information available on long-term cure rates.
  • Radiotherapy:
    • Useful treatment for patients with NMSC who cannot or prefer not to be treated by surgery.
    • The cure rates are over 90% for most skin lesions, but the long-term cosmetic outcome, especially for young patients, is worse than for other treatments.
    • The same area cannot be treated twice and so surgery is required for any recurrence.
    • Radiotherapy can also be used in cases when the margins of excision appear to be incomplete on histopathological examination.
    • It should not be used to treat patients with Gorlin’s syndrome because of the carcinogenic potential of low-dose irradiation at the margins of the treated areas.

Sometimes, especially in the very elderly and debilitated, it may be appropriate to provide no treatment (given the slow growth and low risk of many superficial BCCs) or palliative (debulking or radiotherapy) treatment if the tumour is symptomatic.

• Mortality is low because basal cell carcinomas rarely metastasise.
• Recurrent tumours have poorer cure rates than primary tumours.
• Following development of a BCC, patients are at significantly increased risk of developing subsequent BCCs at other sites.¹
• High-risk groups for the development of further basal cell carcinoma include patients with truncal basal cell carcinoma and those presenting with tumour clusters.¹⁰
• Patients with basal cell carcinoma also have an increased risk of developing squamous cell carcinoma and malignant melanoma.
• There may also be a small increased risk of other malignancies, such as cancer of lung, thyroid, mouth, breast, and cervix and also non-Hodgkin's lymphoma.³

• Education on sun avoidance:
  • Avoid UV exposure in susceptible individuals, particularly children and adolescents.
  • Stay out of the sun between 10am and 4pm.
  • Use high factor sun screens.
  • Wear wide-brimmed hats, long-sleeved shirts and trousers.
• Education of patients to seek early assessment if further lesions develop. Earlier treatment is more effective.
• Oral retinoid treatment may prevent or delay the development of new basal cell carcinomas.³