Clinical and diagnostic features of in situ melanoma and superficial spreading melanoma: a hospital based study.

BACKGROUND: Despite the incidence of in situ melanoma is continuously rising; few studies have investigated its clinical and diagnostic features. OBJECTIVE: To investigate clinical and diagnostic features of in situ melanoma compared to superficial spreading melanoma (SSM). METHODS: This is a hospital based, case-control study. Ninety consecutive patients with an in situ melanoma and 90 age and gender matched patients with SSM were enrolled. Main outcome measures were differences in clinical signs that aroused suspicion of in situ melanoma, detection modalities (self-detection vs. incidental detection by a physician), factors conditioning time between first noticing the suspect lesions and the physician visit. RESULTS: Median diameter of in situ melanoma was smaller than SSM (7.5 vs. 9.0 mm, P < 0.024), and 47.8% of in situ melanomas were smaller than 6 mm, in contrast to 25.6% of SSM (P < 0.002). In situ melanoma was mainly detected by a dermatologist (Odds Ratio 2.95 P = 0.018), and in patients with more than 10 melanocytic naevi (Odds Ratio 3.12, P = 0.008). Clinical factors independently associated to early request of dermatological consultation were age older than 45 years (Odds ratio 3.47, P = 0.002) and location of lesion in a difficult observation skin site (Odds ratio 4.20, P = 0.001), but not Breslow's thickness. CONCLUSIONS: Our findings show that in situ melanoma and SSM share similar clinical characteristics and early warning signs. However, in situ melanoma is smaller in size than SSM. This may have important implications for early diagnosis and prevention strategies.