Laterality and site-specific distribution patterns of Lentigo Maligna and Lentigo Maligna Melanoma

Background: Melanoma has been described to have preferential left-sided laterality on the human body. The distribution and invasion patterns of lentigo maligna (LM) and lentigo maligna melanoma (LMM) have not been well described. Methods: This was a cross-sectional, retrospective study at a single, academic center. LM and LMM cases from 2008-2018 in the dermatopathology registry were analyzed. Results: A total of 392 cases were included (241 LM and 151 LMM). There was no laterality preference overall. The only exception were neoplasms located on the head/neck, which showed a left-sided laterality. LM and LMM had the highest incidence on the head/neck, followed by upper extremities, trunk, then lower extremities. Men had a higher incidence on the head/neck and trunk, while women had a higher incidence on the extremities. Interestingly, the upper extremities and the right side of the female body had a higher propensity for invasive lesions. Conclusion: While melanomas demonstrate preferential left-sided laterality, LM and LMM only share this pattern in respect to the head/neck region. Our results complement previous study findings which characterize LM and LMM as a head/neck and upper extremity pathology. Finally, our study suggests that certain body sites and laterality have an increased propensity for invasion.