DIFFERENTIATION IN PEDIATRIC PERIPHERAL PRIMITIVE NEUROECTODERMAL TUMORS OF BONE - A CRITICAL CONTRIBUTION TO ITS ASSESSMENT

Differentiation was studied in 73 paediatric peripheral primitive neur orectodermal tumours (pPNETs) of bone observed during 1974 through 199 2. The presence of rosettes, pseudorosettes, and/or a rosette-like arr angement of tumour cells (the morphological neural marker, MNM) occurr ed in 29% of these cases. NSE and NCAM were expressed by nearly all tu mours; synaptophysin was present in 30% of cases, not significantly as sociated with the MNM status. Neuroendocrine (NE) markers were present in 25% (chromogranin B, secretogranin II) to 40% (chromogranin A, 7B2 protein) of cases. Focal expression of cytokeratins, S100 protein and /or des min was also noted in a minority of cases. In univariate stati stical analysis, only the presence of MNM conferred a significantly hi gher (about twofold) risk of death than its absence. This study demons trates the occurrence of at least one immunocytochemical N and/or NE d ifferentiation marker in all pPNETs of bone and a focal expression of cytokeratins, S100 protein and/or desmin in a minority of cases. Synap tophysin and MNM were present each in less than 1/3 of the cases, and no association was noted between them. Statistical analyses highlighte d the prognostic role of MNM per se and discourage the sole use of imm unocytochemistry in the assessment of neuroectodermal differentiation for prognostic purposes in paediatric pPNETs of bone.