Mucosal melanoma: correlation of clinicopathologic, prognostic, and molecular features

Although the presence of the t(12;22)(q13;q12) translocation (the defining molecular feature of malignant melanoma of soft parts/clear cell sarcoma) in cutaneous melanoma has been investigated, no large-scale studies have been performed among mucosal melanoma (MucM). In this study we assessed the prevalence of the EWSR1 rearrangement in primary MucM, and analyzed gross and microscopic features with their potential impact on diagnosis and prognosis. Overall, 132 specimens from 84 patients were included. A total of 55 cases had an intramucosal component. Survival of MucMs of the head and neck was associated with two independent factors: size and histology. Tumors more than 3 cm in greatest dimension had an average survival of 12.75 months; those 3 cm or less had an average survival of 38.3 months (P=0.035). Purely epithelioid tumors had an average worse survival of 16.8 months (P=0.028). A cut-off value of 1 mm for Breslow depth provided a statistically significant difference in survival at both 3 and 5 years (P=-0.02) by multivariate analysis in the gynecologic tract. At the molecular level three cases had a EWSR1 rearrangement by fluorescent in-situ hybridization, but only one with an intramucosal component. None of the 58 cases tested by PCR showed the presence of the EWSR1 rearrangement. With the exception of vulvar melanomas, the prognosis of mucosal-associated melanomas was poor and there was a suggestion that spindle morphology may be more favorable. Our study also showed that the EWSR1 rearrangement was very uncommon among MucM. Though 'clear cell sarcoma' is embedded in the sarcoma literature, the synonym 'melanoma of soft parts' has considerable justification in light of our evolving understanding of the molecular genetics in the family of malignant melanomas.