Diagnosis and prognostic indicators

GPs should refer, via the urgent suspected cancer (USC) referral pathway, all patients in whom melanoma is a strong possibility rather than carry out a biopsy in primary care.

A suspected melanoma should be excised with a 2 mm margin and a cuff of fat.

If complete excision cannot be performed as a primary procedure an incisional or punch biopsy of the most suspicious area is advised.

A superficial shave biopsy is inappropriate for suspicious pigmented lesions.

The macroscopic description of a suspected melanoma should:

• state the biopsy type, whether excision, incision, or punch
• describe and measure the biopsy (in mm) state the size of the lesion in mm
• and describe the lesion in detail (shape, pattern of pigment distribution, presence or absence of a nodular component and presence or absence of ulceration).

Selection of tissue blocks:

• the entire lesion should be submitted for histopathological examination
• the lesion should be sectioned transversely at 3 mm intervals and the blocks loaded into labelled cassettes
• cruciate blocks should not be routinely selected (they limit the assessment of low power architectural features such as symmetry), however they can be useful when the lesion is close to a polar margin.
• cruciate blocks may be used to assess margins in very large LM excisions.

The Royal College of Pathologists recommend the following core features to be included in the pathology report for invasive melanoma:

Pathologists responsible for reporting melanocytic lesions must be aware of the diagnostic pitfalls in this area. Participation in appropriate continuing professional development (CPD) and external quality assurance (EQA) activity is advisable.

Cases where significant diagnostic doubt exists should be referred for specialist dermatopathology opinion.

The surgical report for completion and therapeutic lymph node dissections should include:

Macroscopic features:

• size of specimen in three dimensions
• the presence (and size) or absence of a macroscopic abnormality
• the presence or absence of a localisation marker
• matted nodes (stage pN3b).

Microscopic features:

• the exact number of nodes identified in total within the specimen
• the number of nodes containing metastatic disease and whether the apical node is involved or not
• the presence or absence of extracapsular spread
• whether the margin of the specimen is involved by tumour.

The sentinel lymph node report should include:

Macroscopic features:

• dimensions of overall specimen
• the presence or absence of a macroscopic abnormality
• the presence or absence of dye in the tissue
• the presence or absence of a localising marker.

Microscopic features

• the number of sentinel lymph nodes
• the number of nodes involved
• for each positive node:
• the location and pattern of deposits
• whether or not the deposits are subcapsular only
• whether, if present, the parenchymal deposits are localised (≤3 deposits) or multifocal (>3 deposits)
• whether the tumour burden (maximum dimension of the largest tumour deposit) is <0.1 mm, 0.1–1.0 mm or >1.0 mm
• the presence or absence of extracapsular extension.