Summary of the morphological, immunohistochemical, and molecular features of melanocytic skin lesions
| Feature | BN | MDN | Early CMM | Refs |
|---|---|---|---|---|
| BN, benign naevi; CMM, cutaneous malignant melanoma; MDN, melanocytic dysplastic naevi; MMR, mismatch repair; MSI, microsatellite instability; TSG, tumour suppressor gene. | ||||
| Clinical | ||||
| Symmetry | Symmetrical | Asymmetrical | Asymmetrical | 5–8, 9 |
| Size | Small (<5 mm) | Larger (>5 mm) | Variable | 5–8, 9 |
| Border | Regular | Irregular | Irregular | 5–8, 9 |
| Colour | Uniform | Variegated | Variegated | 5–8, 9 |
| Histological | ||||
| Cytological atypia | Absent | Mild to severe | Severe | 5–8, 9 |
| Architectural atypia | Absent | Mild to severe | Severe | 5–8, 9 |
| Ultrastructural | ||||
| Melanosomes | Normal | Aberrant | Aberrant | 10, 11 |
| Golgi | Normal | Well developed | Well developed | 10, 11 |
| Mitochondria | Numerous | Abundant | Abundant | 10, 11 |
| Immunohistochemical | ||||
| MMR protein expression | Strong | Intermediate | Decreased | 12 |
| p53, HMB45 expression | Absent | Intermediate | Pronounced | 13, 14 |
| Proliferation marker expression | Low | Intermediate | High | 15–17 |
| Genetic | ||||
| MSI | Absent/Present | Present (+) | Present (+++) | 18, 19 |
| Allelic loss | Absent | Present (+) | Present (+++) | 20–22 |
| Loss of TSG (p16 and p53) | Absent | Present (+) | Present (+++) | 23 |
| Alterations of oncogenes (ras) | Absent | Present (+) | Present (+++) | 24 |