Reason for incorrect identification of cases and controls
| Melanoma | ||||
| Type of misclassification | Umbria | ASL Napoli 3 | Friuli Venezia Giulia | |
| False positives | ||||
| 1 | Histological examination missing | 6 | 15 | 7 |
| 2 | Negative histology | 7 | 12 | 15 |
| (a) Melanoma in situ | – | – | 11 | |
| (b) Negative histology of wide excisions of previous melanoma | 7 | 6 | – | |
| (c) Negative histology (nevus, hyperplasia, dysplasia, verrucoid lesion) | – | 4 | 4 | |
| (d) Basal cell carcinoma | – | 2 | – | |
| Total | 13 | 27 | 22 | |
| False negatives | ||||
| 1 | Possible melanoma relapse | – | – | – |
| 2 | Possible melanoma metastasis | – | 1 | – |
| 3 | Skin cancer of unclear histology | – | – | 1 |
| Total | – | 1 | 1 | |