Differential Clinicopathological Features in Spontaneous Regression of Melanomas and Melanocytic Naevi

: The aim of this study was to determine the clinical, histological and/or immunohistochemical features that enable differential diagnosis of regression of melanocytic naevi from regression of melanomas. All melanocytic neoplasms with histologically-confirmed regression diagnosed in our hospital between 2002 and 2009 were reviewed retrospectively. Lamellar and delicate fibrosis were associated with melanocytic naevi (p <0.0001 and p = 0.021, respectively). Compact fibrosis, high vessel density and higher number of granzyme B+ lymphocytes were associated with malignant melanoma (p = 0.011, p = 0.005 and p = 0.013, respectively). Density of inflammatory infiltrate (p = 0.016), vascular proliferation (p = 0.005), epidermal atrophy (p = 0.009), rate of apoptosis (p = 0.046) and granzyme B immunoreactivity (p = 0.013) was more common in severe-dysplastic naevi and melanomas than in the remaining melanocytic naevi. Logistic regression demonstrates that 5 variables (age, lamellar fibrosis, melanophages, vessel density, and granzyme B immunostaining) would serve to classify appropriately 87% of melanomas among melanocytic lesions with complete regression.