INVOLVEMENT OF THE LONG ARM OF CHROMOSOME-9 IN MEDULLOBLASTOMA IN AN ADULT

Medulloblastoma is the most common primitive neuroectodermal tumor (PN ET) in children, but is very rare in adults. An isochromosome for the long arms of 17, i(17q), is found in about 30% of pediatric cases. Cyt ogenetic studies in adults are very scarce: only six cases have been d escribed cytogenetically: three cases had normal karyotype, two were s tudied partially, and another presented only two clonal structural ano malies: del(9)(q12) and del(11)(q22). We studied the chromosomes from medulloblastoma in a 27-year-old woman and found one hypotetraploid st emline with clonal alterations. In the structural anomalies, chromosom es 3, 9, 12, and i(17q) were involved. Chromosome 9 presented a deleti on in the long arm, del(9)(q13), with consequent loss of the 9q13-->qt er region. This anomaly was similar to one found in a previous case. W e suggest that the partial loss of the long arm of chromosome 9 may be a characteristic change of adult medulloblastoma. (C) Elsevier Scienc e Inc., 1997.