Geometric cutaneous melanoma: a helpful clinical sign of malignancy?

Abstract

Malignant melanomas change shape in a random pattern, with ovoid, crescentic, or nodular shapes seen most frequently. We have observed a number of malignant melanomas that have presented with a geometric, angular shape and have noted that pigmented lesions with this configuration are often found to be malignant. We present 20 patients with malignant melanoma whose lesion displayed a geometric, angular shape. Before excision for formal histopathology, all lesions were scored using the seven-point checklist and ABCDE systems and were divided into low-risk or significant risk of melanoma. Five different geometric shapes were observed. Depending on the scoring system employed, 20% to 40% of the geometric melanomas were considered to be of low risk of malignancy. The development of geometrical angular patterns in a malignant melanoma may represent a morphologic growth pattern that can be used as a clinical risk sign. Even apparently benign low-risk lesions with a geometric shape may pose a significant risk of malignant melanoma. By definition, the majority of lesions that are morphologically geometric are symmetrical in shape, which is more in favor of a benign diagnosis. This may increase the likelihood that early cutaneous melanomas with a geometric shape may be missed. Any pigmented lesion with a geometric configuration should raise the clinician's suspicion of malignancy even if considered otherwise to be of low risk by the standard melanoma checklists.