Geometric Cutaneous Melanoma: A Helpful Clinical Sign of Malignancy?

Background. 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. Methods. 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. Results. 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. Conclusion. 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.