National comprehensive analysis of characteristics of acral lentiginous melanoma

Background/Aim: Acral lentiginous melanoma (ALM) is the least common subtype of cutaneous melanoma and typically occurs on the palms, soles, and nails. Tumor characteristics and disease severity in the US population are not well understood. Our aim was to analyze the characteristics of ALM of the extremities. Patients and Methods: We queried the National Cancer Database to identify patients with the diagnosis of ALM and common malignant melanoma located in the extremities (CMME). We compared demographic, tumor, and treatment characteristics between patients with ALM and those with CMME. Statistical analysis was performed with chi-squared test and multivariate logistic regression models. Results: We identified 5,203 patients with ALM and 118,485 with CMME. When compared with patients with CMME, those with ALM were more likely to be older than 80. years at diagnosis [odds ratio (OR)=2.85, 95% confidence intervaI (CI)=2.12- 3.82; p<0.001], have stage III disease (OR=4.22, 95% CI=1.47-12.16; p=0.01), and have ulceration (OR=1.52, 95% CI=1.33-1.74; p<0.001). Moreover, patients with ALM were less likely to have a mitotic count of 1/mm2 or greater (OR=0.57, 95% CI=0.48-0.67; p<0.001). No statistical difference was found for sex, lymph node involvement, regression, and use of surgery, radiotherapy, and immunotherapy between groups. Conclusion: Age, disease stage, ulceration, and mitotic count are independent factors associated with ALM. Knowledge of the disease characteristics may allow for better diagnosis and understanding of disease pathophysiology.