The differential diagnosis of a posterior mediastinal mass is fairly wide, but at this age, the sympathetic chain tumors predominate.
Microscopic examination shows two cell populations; the first neuroblastic cells are small round primitive cells with high nuclear to cytoplasmic ratio with scant cytoplasm, salt and pepper chromatin pattern and inconspicuous nucleoli. The second ganglionic cells are large cells with prominent nucleoli, abundant granular eosinophilic cytoplasm and distinct cell borders. The cells are arranged in an interspersed, sharply defined, an encapsulated body with differentiate neuroblastic cells (more than 5%); surrounded by a stroma rich of spindle cells and Schwannian cells which are positive for S100. Areas of cystic degeneration, hemorrhage, dystrophic calcification and necrosis are identified.
Synaptophysin is positive in the neuroblasts and ganglionic cells, and Ki67 shows low mitotic index, S100 is positive in Schwann cells.
Diagnosis: Ganglioneuroblastoma, nodular sub-type.