Regional lymph node infiltration and thick lesions are associated with poor prognosis in high-risk resected melanomas: A retrospective cohort study.

Background: Acral lentiginous and mucosal melanoma that represent lesions without cumulative sun-induced damages account for 65% of melanomas among Asians but constitute only 5% in Caucasians. The distinct clinical manifestations might influence the clinical course, response to treatment, and outcomes. Factors associated with the prognosis of high-risk resected melanoma in Asians are still rarely reported.

Methods: Clinical, histological determinants of non-distant metastatic melanoma patients who underwent complete resection in 2014-9 were analyzed.

Results: Mucosal melanoma, nodular melanoma, and acral lentiginous melanoma accounted for 45.1%, 40.2%, and 14.2% of total melanoma cases (N = 82), respectively. Among cutaneous melanomas, all patients were diagnosed with Breslow's depth more than 4 mm (T4), 51% with ulceration, 95.6% with diameter more than 6 mm, 59% with lympho-vascular invasion, and 74% with regional lymph node infiltration. In mucosal melanomas, 78.3% were diagnosed in advanced stages, 14.5% with regional spread to lymph nodes and 77% with regional infiltration beyond mucosa. Lesions with ulceration were associated with higher risk of distant metastasis (OR 3.003, 95%CI:1.01-9.09). Infiltration into regional lymph node was associated with shorter overall survival (median survivals were 17 vs 23.4 months, Mantel-Cox test  = 0.049). Patients diagnosed at Breslow T4 were also associated with poorer overall survival than T1-3 (median survivals were 23 vs 32 months, Mantel-Cox test  = 0.047).

Conclusion: The majority of melanoma patients in our population were diagnosed in advanced stages with a higher risk for recurrence and progression into distant metastasis. Regional lymph node involvement and thicker tumor (T4) were associated with poor prognosis.