Clinical features of skin lesions

Created 2017.

Skin cancers and precursor lesions should be identified and removed.

• Melanoma and melanoma in situ
• Squamous cell carcinoma, intraepidermal carcinoma and actinic keratoses (where practical)
• Basal cell carcinoma

Benign skin lesions should be identified. They don’t need removal, unless:

• They appear suspicious for skin cancer
• They are causing symptoms
• The patient requests removal and accepts the consequences (eg scar)

General characteristics of skin cancer are:

• Enlarging or changing over time (weeks to years)
• Irregular in shape, surface, colour, structure
• May bleed or ulcerate without injury

General characteristics of benign skin lesions are:

• Stable  
• Uniform in surface, colour, structure
• Often symmetrical in shape
• Any bleeding or ulceration is due to recent injury 

Melanoma

• ABCDE characteristics
  • Asymmetry, Border irregularity, Colour variation, Diameter > 6 mm (or Different), Evolving
  • Typical of superficial forms of melanoma
  • Not always present, especially in nodular melanoma
• Glasgow 7-point checklist

Major features:

• Change in size
• Irregular shape
• Irregular colour

Minor features:

• Diameter >7mm
• Inflammation
• Oozing
• Change in sensation
  • Useful for invasive melanoma
  • May miss in-situ melanoma
• A changing/enlarging lesion
  • This may or may not be observed
  • Benign lesions can change
• Asymmetrical/irregular/variable colour, structure, surface
• Shape is often irregular
  • Sometimes, melanoma is round
• Size is often > 6 mm
  • Melanoma can be diagnosed when much smaller
• Even experts miss some cases of melanoma
  • They can look similar to other lesions, especially seborrhoeic keratoses, solar lentigines and benign naevi
  • Be vigilant!

When evaluating pigmented lesions, especially if of concern to the patient, explain that diagnosis can be difficult:

• Early melanoma often looks the same as a mole or freckle.
• Most lesions that concern patients are entirely harmless.
• Self skin examination is useful.
• Any changing lesion, including any evaluated on this occasion, is worth showing to your doctor.
• If the patient is concerned for any reason, return for re-evaluation.
• A second opinion can be obtained using Teledermatoscopy.
• The lesion could be excised for pathological examination.

Most melanomas arise from normal skin. Precursor lesions include:

• Melanocytic naevus: any kind.
• Giant congenital melanocytic naevi > 40 cm diameter.
• Atypical lentiginous hyperplasia and atypical junctional naevus of the elderly. These are irregular pigmented patches in sun damaged skin of face, neck, upper trunk but clinical/dermatoscopic/histopathological characteristics do not meet criteria for diagnosis of melanoma.  

If the lesion is likely benign, explain reasons against unnecessary excision:

• Unnecessary expense.
• Unnecessary scar.
• Unnecessary risk of complications eg infection, haemorrhage, delayed wound healing, drug allergy.
• Pathological diagnosis can also be uncertain or incorrect.
• Patient has other similar lesions that are not concerning to the patient or to their doctor.

Also explain the reasons that partial biopsy is generally avoided.

• Melanoma can be focal within a skin lesion and partial biopsy may miss it.
• Pathological diagnosis is very difficult and the pathologist needs a large sample to be confident.
• Biopsy result can be misleading.

Invasive squamous cell carcinoma

• Grows over weeks to months.
• Tender, painful plaque or nodule.
• It has a dermal component. Palpation often detects a rubbery component within the skin.
• Well-differentiated SCC is scaly, warty.
• Undifferentiated or anaplastic SCC may be difficult to distinguish from other epithelial cancers or even from melanoma histologically.
• These lesions often present as nonspecific enlarging ulcers or ulcerated irregular plaques.

Precursor lesions are actinic keratoses and intraepidermal carcinoma for SCC.

Basal cell carcinoma

• Grows over months to decades
• Early bleeding and ulceration
• Pearly nodule, plaque or edge
• May be skin coloured or pink
• Superficial BCC is an irregular plaque with small erosions and light scale

There is no precursor lesion for BCC.