Fetal origin of the medulloblastoma: evidence from growth analysis of two cases.

Growth analysis of medulloblastomas was performed in two children. They initially manifested symptoms at the age of 3 years and 9 months and at the age of 2 months respectively. Computerized tomography (CT) scans were obtained at different points in each case. The growth curves were drawn on a semilogarithmic graph by calculating the tumor volume on CT on the assumptions that the tumor started from a single tumor cell and that the growth rate was constant. By extrapolating the curves back, tumor inception was estimated to have occurred respectively at the 14-23rd week and at the 16-17th week of gestation. Additional cell kinetic data were obtained from DNA analysis of surgical pathology specimens. Calculated cell-cycle times were 22-32 h for both cases. The S phases comprised 26.3% and 27% and the G0G1 phases 66.8% and 62% of the cell cycle, respectively, for case 1 and 2. Assuming a labelling index of 14%, the cell loss factors were estimated to be 97% and 74% (case 1 and case 2 respectively). The seventeenth week of gestation in humans corresponds to the timing of events occurring postnatally at days 3-18 in the developing cerebella of rodents, i.e., at the time of maximal activity in the migration and differentiation of the cells of the fetal external granular layer. Medulloblastomas have been experimentally induced in rodents by the injection of oncogenic viruses during the neonatal period, and statistical data on the epidemiology of human medulloblastomas have suggested a possible association with the contamination of polio vaccine by the SV 40 virus.(ABSTRACT TRUNCATED AT 250 WORDS)