Clinicopathologic features correlated with paradoxical outcomes in stage IIC versus IIIA melanoma patients

Under current AJCC staging criteria, stage IIC patients paradoxically have worse outcomes than IIIA patients despite the lack of nodal metastatic disease. This study sought to identify additional clinicopathologic characteristics correlated with worse patient outcomes. Retrospective chart review of stage IIC and IIIA melanoma patients were evaluated between 1995 and 2011 with clinical follow-up through 2015. Records were reviewed for demographics, clinical characteristics, and tumor pathology. Fisher's exact test and Wilcoxon's rank-sum test were used to assess group differences. Clinicopathologic features were evaluated relative to overall survival (OS), time to distant metastases, and local/regional recurrence. Overall, 128 patients were included (45 stage IIC and 83 stage IIIA) with a median follow-up time of 5.7 years. Compared with stage IIIA patients, stage IIC patients were older, and their melanomas were more likely to be nodular, amelanotic, thicker, have higher mitotic rate, tumor lymphocytic infiltrate, no radial growth phase, and less likely to have associated precursor lesions. Stage IIC patients had shorter OS and time to distant metastases; multivariate regression revealed that older age (>55 years) and mitotic rate (>5 mitoses/mm) were independent predictors of OS. Melanomas in stage IIC disease may be biologically distinct from those that are seen in stage IIIA. While sentinel node biopsies remain the standard-of-care, these results suggest that clinicians may want to assess the clinicopathologic characteristics described above to aggressively counsel, screen for distant disease, and consider adjuvant therapy, in particular for older patients and higher mitotic rates in thicker primary tumors, regardless of nodal status.