Neuroendocrine differentiation in a large series of genetically-confirmed Ewing's sarcoma family tumor: Does it provide any diagnostic or prognostic information?

Given the potential for neuroendocrine differentiation in Ewing's sarcoma family of tumors (ESFT), we aimed to determine neuroendocrine expression in a large series of genetically-confirmed ESFT and its prognostic significance in clinically-localised neoplasms (n = 176). Slides prepared from tissue microarrays were stained for Insulinoma-associated protein 1 (INSM1), CD56, chromogranin-A and synaptophysin. INSM1 expression was present in 59% of ESFT, while synaptophysin, chromogranin-A and CD56 were expressed in only 13%, 8% and 5% of ESFT, respectively. Histological subtypes were only significantly correlated with INSM1 (p = 0.032) or CD56 (p = 0.016) immunoexpression. Regarding prognosis, no significant association was found between INSM1, synaptophysin or chromogranin-A immunoexpression and progression-free survival (PFS) or overall survival (OS). Despite the low proportion of tumors with CD56 immunoreactivity, CD56 expression was shown to correlate with both poor PFS (p < 0.001) and poor OS (p < 0.001) in the present series. In conclusion, neuroendocrine differentiation is often present in ESFT, and in the present study INSM1 expression in particular was found to be higher than previously described in Ewing's tumors. Nevertheless, this finding does not distinguish these tumors from other round cell tumors that may show focal or diffuse neuroendocrine differentiation. CD56 expression could be used as a prognostic factor in ESFT, although given the results herein obtained, we recommend a prospective validation in independent series including localized and disseminated tumors in ESFT.
(Published by Elsevier GmbH.)