Basal Cell Carcinoma (Rodent Ulcer)

Basal cell carcinomas typically occur in areas of chronic sun exposure. They are usually indolent with slow progression. They can be extensively locally destructive but do not usually metastasise.

• Basal cell carcinoma is the most common skin malignancy in white people.¹
• The incidence of basal cell carcinoma shows marked geographical variation.
• The age standardised incidence of basal cell carcinoma in south Wales was estimated at 114.2 per 100 000 population in 1998.¹
• 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 Factors

• Exposure to ultraviolet radiation²
• Skin type 1 (always burns, never tans), red or blonde hair, and blue or green eyes have been shown to be risk factors.¹
• History of frequent or severe sunburn in childhood
• A positive family history of skin cancer
• Patients on immunosuppressive treatment
• High-risk groups for the development of further basal cell carcinoma include patients with truncal basal cell carcinoma and those presenting with tumour clusters.³
• History of arsenic poisoning

• 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.
• The other patterns of basal cell carcinoma include:
  • 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; 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

• 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
  • Localized scleroderma

Several genetic conditions (including albinism and xeroderma pigmentosa) are associated with an increased risk of developing basal cell carcinoma.

Diagnosis is initially clinical but biopsy of the lesion may be required.

Surgery and radiotherapy appear to be the most effective treatments with surgery showing the lowest failure rates. There is only limitied evidence of the effectiveness of other treatment modalities compared to surgery.^4,5

• Excision with primary closure, flaps and grafts: an excision margin of 4 mm around the tumour is recommended where possible.¹ Cure rates are in the region of 95%.
• Cryotherapy, curettage and cautery: curettage and cautery are not recommended for recurrent, large, morphoeic tumours or tumours on the face. Disadvantage of not enabling confirmation of histology or adequate removal. However the overall cure rate is over 90% for low-risk BCCs.
• Mohs' micrographic surgery: high cure rates;² Serial sections are taken and examined histologically until all margins are clear. Morphoeic and recurrent tumours are best treated by Mohs' micrographic surgery where this is available.¹ Overall cure rates for primary BCC are almost 100% and 95% for recurrent BCC.
• Radiotherapy: generally used for elderly patients with extensive lesions when major surgery may not be appropriate. Cosmetic results are worse than for those removed by excision. Cure rates are approximately 90%. Radiotherapy can also be a useful adjunct treatment for aggressive tumours or when surgery has failed to clear the margins of the tumour.
• Photodynamic therapy: effective for superficial basal cell carcinoma. Topical delta-aminolaevulinic acid becomes photosensitive and subject to photodestruction when exposed to light. The average clearance rate for superficial basal cell carcinoma is about 85% but is lower in nodular basal cell carcinoma.¹
• Topical fluorouracil: useful in the management of multiple superficial basal cell carcinoma on the trunk and limbs. Cure rates are in the region of 80%. 5-fluorouracil only penetrates 1 mm into the skin but new vehicles to enhance absorption are being investigated
• Topical imiquimod: a newer topical immunomodulatory treatment. Has been shown to achieve clearance rates ranging from 70% to 100%. More effective for superficial than nodular tumours.²

• Mortality is low because basal cell carcinoma rarely metastasises.
• Recurrent tumours have poorer cure rates than primary tumours.
• Patients with basal cell carcinoma have an increased risk of developing further basal cell carcinoma, 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.¹

• Education on sun avoidance.
• 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.¹