Geometric border as a marker for melanoma diagnosis: Study of 200 consecutive melanocytic lesions.

The ABCD rule has long been proposed as a guidance for malignant melanoma (MM) diagnosis. We aimed to define a new simple, straightforward tool that could be useful in early melanoma detection and must be validated in further studies. We conducted a prospective historic cohort study of 200 melanocytic lesions classifying them according to the presence of geometric borders. Sixty-four percent of the MM and 31% of the melanocytic nevi presented with geometric borders. Lesions with two straight borders that formed a noncurvilinear angle presented a 2.1-fold higher risk of being malignant after excision. When comparing melanomas with geometric and nongeometric border, we found a tendency toward better prognostic markers in the geometric lesions. Lesions located in the extremities and melanoma subtype SSM were more common in the geometric group. Regarding pathologic features, a deeper Breslow (mean, 3.8 vs 1.4 mm), presence of ulceration (25% vs 5%) and a higher number of mitosis was found in the nongeometric group. On the other hand, more regression was found in the geometric group while both groups showed similar degree of lymphovascular infiltration. We propose geometric border as another clinical criterion to take into account when suspecting MM, which must be validated in further studies. The ABCDE rule could be completed with a G for geometry.