Can morphology predict 1p/19q loss in oligodendroglial tumours?

To investigate the relationship between phenotype and genotype in oligodendroglial tumours and evaluate whether 1p/19q status can be reliably predicted from histological findings.

Three neuropathologists reviewed the association between 10 histological variables, location and genetic losses at 1p, 19q and 17p13 in 63 oligodendroglial tumours (cohort 1). Based on these findings, a multiple logistic regression model for prediction of 1p/19q status was constructed. The ability of this model to predict 1p/19q status was tested on cohort 2, comprising 20 oligodendroglial tumours. Loss of heterozygosity at 1p, 19q and 17p13 was analysed using polymerase chain reaction. Combined 1p/19q loss and losses at 17p13 were mutually exclusive (P < 0.001). The variable H1a (more or <50% of cells with round, uniform nuclei and perinuclear halos) demonstrated the strongest association with 1p/19q status (odds ratio 11.9, 95% confidence interval 3.6, 39.6, P < 0.001). Calcifications, absence of gemistocytic cells and a non-temporal/non-insular location were also associated. The correct 1p/19q status was predicted in 80% of cases in cohort 2.

There is a strong association between phenotype and genotype in oligodendroglial tumours. However, even when all significant variables are accounted for, perfect prediction (100%) of 1p/19q status cannot be obtained.