Investigation

The key investigation for melanoma is excision biopsy with careful pathological analysis.

• a suspected melanoma lesion or where melanoma needs to be excluded, the lesion should be photographed and then excised completely
• the optimal specimen should include the whole tumour with a clinical margin of 2 mm of normal skin, and a cuff of fat
  • this enables to examine the entire lesion and also helps in subsequent treatment which is based on Breslow thickness (1)
• the axis of excision should be oriented to facilitate possible subsequent wide local excision e.g. - on the limb this will be along the long axis and transversely over joints (2)
• shave biopsies should not be performed
• incisional or punch biopsy can be used occasionally e.g. – in differential diagnosis of lentigo maligna on the face or of acral melanoma (not carried out in primary care) (1)

Further investigations and imaging depends on the stage of melanoma and include:

• FBC
• urine melanogens
• CXR
• LFT's
• CT scan
• sentinel lymph node biopsy (SLNB) (3)
• FNAC

With respect to imaging NICE suggest (5):

• offer CT staging to people with stage IIC melanoma who have not had sentinel lymph node biopsy, and to people with stage III or suspected stage IV melanoma
• include the brain as part of imaging for people with suspected stage IV melanoma
• consider whole-body MRI for children and young people (from birth to 24 years) with stage III or suspected stage IV melanoma
  
  

Reference:

• (1) Marsden JR et al. Revised U.K. guidelines for the management of cutaneous melanoma 2010. Br J Dermatol. 2010;163(2):238-56
• (2) Scottish Intercollegiate Guidelines Network (SIGN) 2003. Cutaneous melanoma. A National Clinical Guideline
• (3) Morton DL et al.Sentinel-node biopsy or nodal observation in melanoma. N Engl J Med. 2006;355(13):1307-17.
• (4) Thirlwell C, Nathan P. Melanoma-part 2: management. BMJ. 2008;337:a2488
• (5) NICE (July 2015).Melanoma: assessment and management