Pleomorphic (anaplastic) neuroblastoma.

Four very unusual cases of neuroblastoma in children are reported. Clinically, they had a similar presentation: advanced disease at onset, diffuse abdominal spread, poor treatment response, and rapid progression. Pathologically, the four cases were characterized by a striking degree of cellular and nuclear pleomorphism and anaplasia with bizarre and monstrous expressions. Although some authors have referred to the immature ganglion cells found in neuroblastoma as "bizarre ganglion cells," they usually mean the enlarged, maturing neuroblasts that are typical of ganglioneuroblastoma but far from the extreme anaplasia seen in our cases. A correlation between the clinical course and the histological picture could be hypothetically suggested, but additional evidence and confirmation is needed. These cellular aberrations might represent an unsuccessful and impaired attempt at maturation. Independent from prognosis, the definition of anaplastic neuroblastoma is a useful conceptual specification in the study of this tumor and of giant cell and pleomorphic malignant neoplasms of childhood.