[Morphology of neuroblastoma. Light and electron microscopic studies as a contribution on diagnosis and differential diagnosis].

The neuroblastoma is one of the most frequent malignant solid tumors in childhood and is thus of great practical importance. The origin of neuroblastoma cells from neural crest derivatives is generally accepted now, and this histogenesis explains some biochemical and morphological characteristics of the tumor. The cytological and histological features of neuroblastomas can be rather varying and, therefore, the diagnosis and differential diagnosis may be difficult. Our study presents the findings of 48 neuroblastomas after light microscopic examination and the ultrastructural characteristics of 8 neuroblastomas and 1 ganglioneuroma. At light microscopic level, completely undifferentiated neuroblastomas and tumors with variable degrees of differentiation were identified. The differentiation of the tumor tissue to ganglion cell-like elements was indicated by an increasing amount of cellular cytoplasm with development of a cytoplasmic process as well as an alteration of the picture of the nucleus (nuclear enlargement and a clearly visible nucleolus). Differentiation to Schwann cell-like elements was occasionally observed, too. Electron microscopically, in all tumors neurosecretory granules could be recognized, and in the better differentiated areas neurite-like cytoplasmic projections were detectable. Thus, the electron microscopy can be a valuable aid in establishing an unequivocal diagnosis. The histology of neuroblastomas is said to be of prognostic significance. Therefore, grading schemes of malignancy were developed. At present, the grading procedure after Hughes and coworkers is mostly used. The criteria of this grading system are presented and interpreted. Finally, those tumors are briefly characterized which play the main role in the differential diagnosis, i.e. juvenile rhabdomyosarcomas, Ewing's sarcoma (including the extraskeletal type), lymphoblastic lymphoma and histiocytic reticulosarcoma. The most important clinicopathologic differences in comparison to neuroblastomas are referred to. Using a large scale of morphologic methods as well as considering clinical and paraclinical parameters, the exact diagnosis of neuroblastoma should be possible in nearly every case.