Several staging systems have evolved for neuroblastoma and The Children’s Oncology Group has produced a risk-based system that includes the status of chromosomal changes (17q, 1p, 11q), but these approaches are under frequent revision.
Treatment is predicated on clinical staging, with the lowest risk category allowing observation because some lesions regress spontaneously. Those patients who are at intermediate risk are treated with chemotherapy and high-risk children have surgical resection and receive intensive chemotherapy, radiation, and in selected cases, hematopoietic stem cell transplantation. The two better-risk strata have survival rates exceeding 90 percent, but the highest risk group has a 30 percent survival rate.
Retinoblastoma Another closely related tumor is retinoblastoma. This proves to be one of the most frequent extracranial malignant tumors of infancy and childhood. Eighty percent develop before the fifth year of life. It is a small cell tumor with neurofibrils and, like neuroblastoma, has a tendency to form rosettes. The tumor develops within the eye and the blindness that it induces may be overlooked in an infant or small child. It is easily seen ophthalmoscopically, because it arises from cells of the developing retina. An abnormal protein encoded by a growth-suppressor or antioncogenic gene (Rb), mentioned earlier in relation to the genetics of brain tumors, has been identified. It is postulated that an inherited mutation affects one allele of the normal gene, and only if this is accompanied by a mutation that eliminates the function of the second allele will the tumor develop. Early recognition and radiation or surgery effect cure.
Ependymoma of the Fourth Ventricle
Ependymomas, as pointed out earlier in this chapter, arise from the lining cells in the walls of the ventricles. Approximately 70 percent of them originate in the fourth ventricle, according to Fokes and Earle (Fig. 30-13). Postmortem, some of these tumors, if small, are found protruding into the fourth ventricle, never having produced local symptoms. Whereas the supratentorial ependymoma occurs at all ages, fourth ventricular ependymomas appear mostly in childhood. In the large series of Fokes and Earle (83 cases), 33 developed in the first decade of life, 6 in the second decade, and 44 after the age of 20 years. Males have been affected almost twice as often as females.
Cerebral ependymomas usually arise from the floor of the fourth ventricle and extend through the foramina of Luschka and Magendie. They may later invade the medulla. These tumors produce a clinical syndrome much like that of the medulloblastoma except for their more protracted course and lack of early cerebellar signs. The histologic features of this tumor were described earlier in this chapter. The degree of anaplastic change varies and has prognostic significance. The most anaplastic form is the ependymoblastoma, a highly aggressive tumor that falls within the spectrum of primitive neuroectodermal tumors (see the following text).
Symptoms may be present for 1 or 2 years before diagnosis. About two-thirds of the patients come to notice because of increased intracranial pressure; in the remainder, vomiting, difficulty in swallowing, paresthesia of the extremities, abdominal pain, vertigo, and neck flexion or head tilt are prominent manifestations. Some patients with impending cerebellar–tonsillar herniation are disinclined to sit and have vertical downbeating nystagmus. Surgical removal offers the only hope of survival. The addition of radiation therapy and sometimes ventriculoperitoneal shunting of CSF may prolong life. Myxopapillary ependymomas of the spinal cord and filum are discussed with the spinal cord tumors further on and in Chap. 42.