Histopathological predictive factors in Ewing's sarcoma of bone and clinicopathological correlations. A retrospective study of 261 cases.

A retrospective multifactorial analysis on 261 previously untreated patients with Ewing's sarcoma (Es) of bone has been carried out in order to ascertain the prognostic value of several histological variables on survival. Among those cases accepted as Es, 208 (80% of the patients) were considered to be "typical Es", while 40 (15%) displayed a large cell predominance, being subclassified as "atypical large cell Es". Furthermore, 13 patients (5%) possessed tumours of endothelial-like appearance. Eleven cases which displayed a mixed histological configuration were finally included within one of the three previous groups according to their predominant histological pattern. After adjustment for therapeutic regimens and initial location of the tumour, only two histological characteristics remain significant; i.e. the presence of necrosis (p = 0.002) and, to a lesser degree, the presence of filagree "en damier" pattern (p = 0.08), both of which are of poor prognostic value. From this study, it can be assumed that the morphological (and possibly histogenetical) heterogeneity of Es of bone has no prognostic influence on survival.