Differential diagnoses: Skin malignancy

Dr Nigel Stollery compares four skin malignancies and offers clues for their diagnosis

Nodular malignant melanoma


  • Malignant tumour of melanocytes
  • More common in fair skin types
  • Genetic component in some cases with a positive family history
  • Two-thirds arise in normal skin, the rest in existing moles
  • ABCDE rule aids diagnosis
  • Survival rates are improving


  • Excision is the mainstay of treatment
  • Prognosis dependent on tumour thickness
  • Research continues, but no curative treatments as yet, except for excision

Nodular basal cell carcinoma


  • Most common skin cancer
  • Often called rodent ulcer, as thought to look like a rat bite
  • More common on sun-exposed areas in fair-skinned individuals
  • Incidence increases with age
  • Usually has a rolled, pearly edge, with central ulceration
  • Slow growing, often over years
  • No metastatic potential


  • Treatment of choice is usually local excision
  • In recurrent cases or large facial lesions, Mohs micrographic surgery can be very helpful
  • In the elderly with large lesions not amenable to surgery, radiotherapy is an alternative

Amelanotic melanoma


  • Malignant tumour of melanocytes
  • Do not make melanin, so lesions are not pigmented
  • Colour usually pink, purple or normal skin colour
  • Diagnosis often late owing to atypical appearance, leading to a poor prognosis
  • Usually have an asymmetrical shape with an irregular border


  • Treatment of choice is surgical excision
  • Metastatic spread can occur, with potential to be fatal

Squamous cell carcinoma


  • Usually occurs on areas of maximum sun exposure
  • Can arise in normal skin, or in lesions such as ulcers
  • May produce keratin, so surface is often scaly or horn-like
  • May ulcerate and bleed
  • Much faster growing than basal cell carcinoma


  • Treatment of choice is surgical excision
  • Potential to metastasise to lymph nodes
  • May be fatal if left untreated
  • Radiotherapy is an alternative if surgery cannot be tolerated

Dr Stollery is a GP in Kibworth, Leicestershire, and clinical assistant in dermatology at Leicester Royal Infirmary

Have you registered with us yet?

Register now to enjoy more articles and free email bulletins


Already registered?

Sign in

Follow Us:

Just published

Vaccination tracker

UK COVID-19 vaccination programme tracker

GPs across the UK have led the largest-ever NHS vaccination programme in response...

RCGP chair Professor Martin Marshall

Hand PCNs control of primary care infrastructure funding, says RCGP

CCG funding for primary care infrastructure should be handed to PCNs when the bodies...

Professor Martin Marshall and Talking General Practice logo

Podcast: RCGP chair Professor Martin Marshall

Talking General Practice speaks to RCGP chair Professor Martin Marshall.

Dr Chaand Nagpaul

In-house review not enough to stop 'unjust' GMC referrals, warns BMA

Doctors' leaders have repeated calls for a full independent review of the GMC referral...


How widespread is long COVID in the UK?

Millions of people in the UK are living with long COVID. GPonline looks at the data...

COVID-19 vaccination sign

GP contract for autumn COVID-19 booster campaign due shortly

GP practices in England will be invited shortly to sign up for the COVID-19 autumn...