PRIMITIVE NEUROECTODERMAL TUMOR OF THE CHEST-WALL

The concept of primitive neuroectodermal tumour (PNET) has been evolvi ng for many years, as has its nomenclature. It was first described as a tumour arising in peripheral nerve, when it was called neuroepitheli oma [1]. These tumours are part of the differential diagnosis of malig nant small round cell tumours, which include Ewing's sarcoma, rhabdomy osarcoma, neuroblastoma and lymphoma, and which appear as sheets of mo notonous small round cells on light microscopy, staining dark blue wit h haematoxylin and eosin. In the 1970's, reports of tumours displaying neural features introduced new terms such as primitive neuroectoderma l tumour and peripheral neuroectodermal tumour. A relationship to the undifferentiated primitive neuroectodermal tumours of the central nerv ous system in children was assumed by the title of these tumours, alth ough it was recognised that they were not necessarily related to perip heral nerves. In 1979, Askin described a series of patients with malig nant small cell tumours of the chest wall which showed neural differen tiation, but which bore a resemblance to Ewing's tumour [2]. Later, th is tumour was also diagnosed at other sites, and became identified wit h the previously described neuroepitheliomas, but the names multiplied , e.g. peripheral neuroepithelioma, peripheral neuroblastoma, Askin tu mour, and peripheral PNET. The term 'primitive neuroectodermal tumour' is used in this article. Cytogenetic studies have confirmed that it f orms part of a spectrum with both classical and atypical Ewing's tumou r [3]. The clinical and pathological features of PNET, its management, and perspectives for the future, are discussed with reference to a ca se of PNET of the chest wall.