This is the microscopic appearance of neuroblastoma, which is one of the "small round blue cell" tumors most typically seen in the pediatric age range. These neoplasms often arise in the adrenal gland; they can reach a large size in the retroperitoneum before detection. They often contain areas of necrosis and calcification. Note the rosette formation, with cells arranged around a center of cellular fibrillar extensions. At higher magnification the round cells with prominent blue nuclei, granular chromatin, and minimal cytoplasm are seen.