Glycogen-containing neuroblastoma with clinical and histopathologic features of Ewing's sarcoma.

The differential diagnosis is difficult in cases of metastatic neuroblastoma, Ewing's sarcoma, lymphoma, and rhabdomyosarcoma, the common so-called small round cell tumors of childhood. The distinction between Ewing's sarcoma and neuroblastoma in bone with no soft tissue mass in the adolescent is especially difficult. Ewing's tumor is usually characterized by its content of glycogen, neuroblastoma by its absence. A case of glycogen-containing neuroblastoma initially misdiagnosed as Ewing's tumor is presented. Diagnostic implications, including the role of electron microscopy in diagnosis, are discussed. Glycogen alone is unreliable as a diagnostic aid due to 1) its presence in several tumors other than Ewing's including neuroblastoma, and 2) its absence in some cases of Ewing's sarcoma.