Differentiation in paediatric peripheral primitive neuroectodermal tumours of bone. A critical contribution to its assessment

Differentiation was studied in 73 paediatric peripheral primitive neurorectodermal tumours (pPNETs) of bone observed during 1974 through 1992. The presence of rosettes, pseudorosettes, and/or a rosette-like arrangement of tumour cells (the morphological neural marker, MNM) occurred in 29% of these cases. NSE and N-CAM were expressed by nearly all tumours; synaptophysin was present in 30% of cases, not significantly associated 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 desmin was also noted in a minority of cases. In univariate statistical analysis, only the presence of MNM conferred a significantly higher (about twofold) risk of death than its absence. This study demonstrates the occurrence of at least one immunocytochemical N and/or NE differentiation marker in all pPNETs of bone and a focal expression of cytokeratins, S100 protein and/or desmin in a minority of cases. Synaptophysin and MNM were present each in less than 1/3 of the cases, and no association was noted between them. Statistical analyses highlighted the prognostic role of MNM per se and discourage the sole use of immunocytochemistry in the assessment of neuroectodermal differentiation for prognostic purposes in paediatric pPNETs of bone.