4.1. Diagnosis
Clinical suspicion should lead to a tissue diagnosis of malignant melanoma. Guidelines for the recognition of high-risk lesions are the following well-known ‘ABCDE’ criteria:
A – Asymmetry
B – Border (irregular)
C – Colour variety (a number of different shades of brown or black, blue, etc.)
D – Diameter (>6 mm diameter)
E – Evolving (any change in size, shape, colour, elevation or any new symptom).
Although these criteria are useful, particularly for the public, it is worth remembering that in fact in the early stages malignant melanomas can be <6 mm in diameter and that approximately 5% of malignant melanomas are actually not pigmented.
Table 3.7. Criteria for urgent referral to a local skin cancer multidisciplinary team.
| A new mole in adulthood with changing shape, colour, size |
| Itching or bleeding |
| Any mole with asymmetry or three or more colours |
| Any new persistent skin lesion, especially if pigmented and the diagnosis is unclear |
| A new pigmented line in a nail |
| A lesion growing under a nail |
Source: Marsden et al. (2010).
Accurate diagnosis is dependent on tissue sampling, and an excisional biopsy is recommended after clinical photography. It is not recommended that this is done in primary care: instead, it should be performed by suitable members of the local skin cancer multidisciplinary team. It is appropriate that the lesion is excised in a manner that allows a further wide excision; excision should include the whole tumour with a 2-mm margin of normal skin and a cuff of fat in order to allow an accurate histological confirmation of diagnosis, Breslow thickness and Clark level (Lederman and Sober, 1985; Austin et al., 1996). Incisional or punch biopsy is sometimes acceptable for specific situations such as facial lentigo maligna (melanoma in situ), but this decision should be made under the guidance of the local skin cancer multidisciplinary team.
The Royal College of Pathologists has produced guidelines for the dataset required in histopathological reports (Association of Directors of Anatomic and Surgical Pathology, 1998). These are summarised in Table 3.8.
Table 3.8. Minimum data set required in histopathological description for malignant melanoma.
| Clinical information | Site | |
| Procedure (excision, re-excision, punch biopsy) | ||
| Macroscopic description | Contour | |
| Colour | ||
| Size of tumour (mm) | ||
| Size of excised specimen (mm) | ||
| Microscopic description | Ulceration | Presence or absence |
| Thickness of the tumour | Measured from the granular layer of epidermis to the deepest dermal malignant cells to the nearest 0.1 mm | |
| Number of mitoses per mm2 | In the area of greatest mitoses in the vertical growth phase | |
| Histological subtype | Superficial spreading, nodular, lentigo maligna, acral lentiginous melanoma | |
| Margins of excision | Indicates whether excision is complete at peripheral and deep margins | |
| Pathological staging | TNM staging should be used | |
| Growth phase | Invasive melanoma without a vertical growth phase is microinvasion | |
| Regression | ||
| Tumour-infiltrating lymphocytes | ||
| Lymphatic or vascular invasion | ||
| Perineural infiltration | Prognostic factor | |
| Microsatellites | Islands of tumour >0.05 mm in the tissue beneath the mass of melanoma, separated by 0.3 mm of normal collagen (Harrist et al., 1984). This is predictive of lymph node metastases | |
| Precursor naevus | Presence should be recorded | |
| Clark level | Less reliable than thickness | |
Source: Marsden et al. (2010).
The Breslow thickness describes how deeply the tumour cells have invaded and is measured using an ocular micrometer from the granular layer of the epidermis to the deepest dermal tumour cells (Breslow, 1970). It is not only an important prognostic factor but also guides clinicians as to the excision margins for wide excision and is one of the criteria used in predicting lymph node metastases.
It is different from Clark levels, which determine the level of anatomical invasion of the tumour cells. Clark levels have been superseded by Breslow thickness, except when the Breslow thickness is <1 mm, when they can offer prognostic value.
This work is copyright the author(s) and is published under a Creative Commons licence. For full details, please see the copyright page in the table of contents.
© 2025 Technology by Armadillo Systems | Privacy statement
