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Reclassification
of oligoastrocytomas by loss of heterozygosity studies
Marica Eoli 1,
Lorena Bissola 2, Maria Grazia Bruzzone
2, Bianca Pollo 1, Carmelo Maccagnano
2, Tiziana De Simone 2, Lorella Valletta
2, Antonio Silvani 1, D Bianchessi
2, Giovanni Broggi 3, Amerigo Boiardi
1, Gaetano Finocchiaro 2 *
1Department of Clinical
Neurosciences, Istituto Nazionale Neurologico Besta, Milan, Italy. 2Department
of Experimental Neurosciences and Diagnostics, Istituto Nazionale
Neurologico Besta, Milan, Italy. 3Department of
Neurosurgery, Istituto Nazionale Neurologico Besta, Milan, Italy
*Correspondence to Gaetano Finocchiaro, Unit of
Experimental Neuro-Oncology, Dept. Experimental Neurosciences,
Istituto Nazionale Neurologico Besta, via Celoria 11, 20133 Milan,
Italy. Email: Gaetano Finocchiaro
(finocchiaro@istituto-besta.it).
Received: 6 June 2005; Accepted: 25 October 2005
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Oligoastrocytomas (OAs) are WHO grade II
or III tumors composed of a mixture of 2 neoplastic cell types
morphologically resembling the cells in oligodendrogliomas and diffuse
astrocytomas.
Investigations on the genetic profile of OAs may yield important
information for their classification and help for their clinical
management.
We have studied, in 94 OAs (46 WHO grade II and 48 WHO grade III), the
patterns of loss of heterozygosity (LOH) of 4 genomic regions: 1p,
19q, 17p and 10q.
Results were as follows: LOH 1p was present in 46% of the tumors; LOH
19q in 45%; LOH 17p in 22%; LOH 10q in 16%.
LOH 1p and 19q were associated in 32%, other LOH associations were
rare (<3%).
Patients had a median follow-up of 30 months.
Patients without LOH on 1p had shorter progression free survival than
patients with LOH on 1p: 30 vs. 132 months, p <
0.0001.
MRI indicated that tumors without LOH on 1p were often temporal (p
< 0.02), and showed signal inhomogeneity on T1 and T2 images (p
< 0.02) and contrast enhancement (p < 0.04).
Thus, LOH on 1p identifies two subgroups of OAs.
OAs without LOH on 1p behave like WHO grade II or III diffuse
astrocytomas: they have shorter survival, MRI characteristics implying
malignancy and genetic alterations associated with tumor
progression.
OAs with LOH on 1p, on the other hand, behave like WHO grade II or III
oligodendrogliomas with 1p loss: they are associated with longer
survival and do not have MRI or genetic alterations associated with
malignancy.
These findings suggest that the definition of OAs or mixed gliomas
could be reshaped in agreement with the genetic information.
Keywords.
Oligoastrocytoma, LOH 1p, LOH 19q, LOH 17p, LOH 10, MRI
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