Sinonasal Mucosal Melanoma: Role of Tumor Proliferative Indices and Pathological Factors in Survival.

Objective: The objective of this study is to determine the association of proliferation indices and pathologic biomarkers on overall and recurrence/metastasis-free survival (OS and RMFS) in patients with sinonasal mucosal melanoma (SNMM) and to assess the genetic mutational landscape of SNMM.

Methods: This is a retrospective cohort study of 45 SNMM patients without neoadjuvant therapy who underwent surgical therapy with curative intent and had tumor tissue available for histopathologic review, molecular analysis, and genetic mutational assessment. The OS and RMFS were assessed for associations with numerous tumor and patient-related factors.

Results: Among proliferative indices, higher Ki67 and mitotic rates were associated with worsened OS and RMFS (Ki67: p = 0.0007 and p < 0.0001; mitotic rate: p = 0.005 and p = 0.0009, respectively). The presence of brisk tumor-infiltrating lymphocytes (TILs) was associated with improved RMFS (p = 0.007) and the presence of lymphovascular invasion was associated with worsened OS and RMFS (p = 0.02 and p = 0.04, respectively). Patients with amelanotic tumors were more likely to have higher T-stage (p = 0.046), less likely to have brisk TILs (p = 0.02) and had worsened RMFS (p = 0.03). Patients on immunotherapy with tumor Ki67 < 40% had better 3-year OS compared to those with higher Ki67 index (p = 0.004). Actionable genetic mutations such as BRAF V600E are rare and present in only 1 of 20 patients tested.

Conclusion: In SNMM patients, pathologic and proliferation markers such as Ki67, mitotic rate and brisk TILs are associated with survival and may be considered in future staging systems. Clinical response to immunotherapy appears to correlate with the Ki67 index. Given the distinct genetic profile of SNMM, targeted therapies against the MAPK kinase pathway have limited utility.

Level Of Evidence: 3 Laryngoscope, 132:2350-2358, 2022.