Clinicopathological predictors of recurrence in nodular and superficial spreading cutaneous melanoma: a multivariate analysis of 214 cases

Background: Nodular melanoma (NM) accounts for most thick melanomas and because of their frequent association with ulceration, fast growth rate and high mitotic rate, contribute substantially to melanoma-related mortality. In a multicentric series of 214 primary melanomas including 96 NM and 118 superficial spreading melanoma (SSM), histopathological features were examined with the aim to identify clinicopathological predictors of recurrence.

Methods: All consecutive cases of histopathologically diagnosed primary invasive SSM and NM during the period 2005-2010, were retrieved from the 12 participating Italian Melanoma Intergroup (IMI) centers. Each center provided clinico-pathological data such as gender, age at diagnosis, anatomical site, histopathological conventional parameters, date of excision and first melanoma recurrence.

Results: Results showed that NM subtype was significantly associated with Breslow thickness (BT) at multivariate analysis: [BT 1.01-2 mm (OR 7.22; 95% CI 2.73-19.05), BT 2.01-4 mm (OR 7.04; 95% CI 2.54-19.56), and BT > 4 mm (OR 51.78; 95% CI 5.65-474.86) (p < 0.0001)]. Furthermore, mitotic rate (MR) was significantly correlated with NM histotype: [(MR 3-5 mitoses/mm² (OR 2.62; 95% CI 1.01-6.83) and MR > 5 mitoses/mm² (OR 4.87; 95% CI 1.77-13.40) (p = 0.002)]. The risk of recurrence was not significantly associated with NM histotype while BT [BT 1.01-2.00 mm (HR 1.55; 95% CI 0.51-4.71), BT 2.01-4.00 mm (HR 2.42; 95% CI 0.89-6.54), BT > 4.00 mm. (HR 3.13; 95% CI 0.95-10.28) (p = 0.05)], mitotic rate [MR > 2 mitoses/mm² (HR 2.34; 95% CI, 1.11-4.97) (p = 0.03)] and the positivity of lymph node sentinel biopsy (SNLB) (HR 2.60; 95% CI 1.19-5.68) (p = 0.007) were significantly associated with an increased risk of recurrence at multivariate analysis.

Conclusions: We found that NM subtype was significantly associated with higher BT and MR but it was not a prognostic factor since it did not significantly correlate with melanoma recurrence rate. Conversely, increased BT and MR as well as SNLB positivity were significantly associated with a higher risk of melanoma recurrence.