Heterozygosity status of 1p and 19q and its correlation with p53 protein expression and EGFR amplification in patients with astrocytic tumors: novel series from India

There are few reports of loss of heterozygosity (LOH) of 1p and 19q in astrocytic tumors, especially glioblastoma multiforme (GBM). We evaluated 1p and 19q (either or both) heterozygosity status in 71 astrocytomas, including 6 pediatric cases: 20 diffuse astrocytomas (DA), 9 anaplastic astrocytomas (AA), and 42 GBM. In the GBMs, p53 protein expression was assessed by immunohistochemistry and epidermal growth factor receptor (EGFR) gene amplification by fluorescence in situ hybridization; TP53 sequencing was done in 15 of the GBMs. In adults, LOH of 1p or 19q was detected in 16% of DAs and 50% of GBMs; none of the AAs showed this alteration. In GBMs, LOH of 19q was most common (26%), followed by combined 1p and 19q LOH (13%) and 1p LOH (10%). Pediatric GBMs also harbored isolated 1p and 19q LOH (50%). Notably, LOH of 1p or 19q LOH was more frequent in p53 immunopositive secondary GBMs (61%) than in primary GBMs (17%). This suggests that LOH of 1p and 19q may be acquired during progression to secondary GBMs. Thus, 1p and 19q LOH can occur in astrocytic tumors, most commonly in secondary GBMs without morphological correlation with an oligodendroglial histology. The clinical significance of recognition of this subset of GBMs is based on several recent reports of association with better prognosis, although long-term follow-up studies are required.