At a glance: Squamous cell carcinoma versus fish tank granuloma

Squamous cell carcinoma (SCC)
Clinical features

  • Usually develops from an actinic keratosis in an area that has been exposed to the sun.
  • Initial thickening of the skin develops into a raised, indurated plaque that becomes nodular and fixed.
  • Margin of the ulcer may be raised and everted.
  • The lesion grows more rapidly than a basal cell carcinoma. 

Management

  • A biopsy may be taken to confirm diagnosis.
  • The treatment of choice is excision with histological confirmation of removal.
  • Cryotherapy, curettage and cautery may prove satisfactory.
  • Radiotherapy is usually successful. 

Fish tank granuloma
Clinical features

  • Often a history of cleaning an infected fish tank.
  • Caused by Mycobacterium marinum. 
  • A pink or purple nodule or pustule forms, which ulcerates or forms an abscess. 

Management

  • A swab culture can confirm the infection.
  • Treatment choices are rifampicin with ethambutol, co-trimoxazole forte or minocycline.
  • Patients should be advised to cover any open wounds before working in suspect water, and to use antibiotic soaps to wash their hands. 

Contributed by Dr Jean Watkins, a GP in Ringwood, Hampshire

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