Transmission and scanning electron microscopic studies on the tumors of neuroblastoma group.

Ultrastructural study of neuroblastoma group tumors including 7 neuroblastomas, 4 ganglioneuroblastomas, and 2 ganglioneuromas was performed by using both TEM and SEM. Tumor cells showed a wide variation comparable to the developmental stages of nerve cells and were classified into four types according to the neuritic process projections; namely apolar, monopolar, bipolar, and multipolar. Neuroblastoma was composed of small cells of apolar, monopolar, and bipolar types with few multipolar cells. Tumor cells ganglioneuroblastoma and ganglioneuroma were multipolar type. SEM observation demonstrated characteristic varicosities in the elongated neuritis processes, and by TEM examination the dilated portions of these varicosities revealed disruption or disappearance of parallel runnings of the microtubules and microfilaments. TEM examination demonstrated presence of Schwann cells in ganglioneuroblastoma and ganglioneuroma, and satellite cells and perineurial cells in ganglioneuroma. The hitherto undescribed cells with caveolar structure which are thought to be a precursor of these stromal elements were disclosed in ganglioneuroblastoma. In order to evaluate the maturation and prognosis of tumors of this group, stromal differentiation seems to be equally important as ganglionic differentiation because both stromal elements and tumor cells have a common origin of neural crest.