ABSTRACT
Retinoblastoma is the most common primary intraocular cancer in children. It arises from cells that are defective in both copies of the retinoblastoma susceptibility gene [RB I]. Loss of both RB1 and p53 functions may be required for cell immortalization and tumor development. The pattern of p53 expression in retinoblastoma appears to depend on the state of differentiation of the tumor. p53 and RB pocket proteins are important to control DNA ploidy, which may have a value in estimating the prognosis of retinoblastoma. The aim of this work was to assess p53 expression, DNA ploidy, and their relations with histopathologic features in retinoblastoma cases. The study was done on eight patients with retinoblastoma [seven males and one female]. Personal and family history with pedigree analysis were done for all cases. Ophthalmic examination with follow up of tumor regression rate during therapy was performed. Eight primary retinoblastoma samples were obtained from enucleated eyes of all patients. Retinoblastoma sections were stained by hematoxylin and eosin stain and scoring of histopathologic features was performed. Sections were immunohistochemically stained for the protein product of the tumor suppressor gene p53 and quantified for the extent and intensity of the staining. DNA ploidy was examined by assessment of type of DNA histogram and DNA index using cytometric analysis system [CAS 200] after feulgen staining. The proliferative activity was automatically expressed by the CAS 200 as the percentage of cells engaged in the S-phase of the cycle. Our results indicated that p53 protein was immunohistochemically detectable in most retinoblastoma cases [7/8 cases], and was only negative in one case. DNA was aneuploid in 6 out of 8 cases, while 2 cases [one of them was p53 negative, and the other showed weak positivity] were diploid with high proliferative activity. Histopathologic examination revealed that 3 cases were poorly differentiated and 5 cases showed intermediate differentiation with increased necrotic changes and mitotic figures. Retinoblastoma samples showed high degree of p53 protein expression and high degree of aneuploidy which were related to the aggressiveness of histopathologic changes of retinoblastoma. Thus both p53 expression and DNA ploidy have been shown to be markers of aggressiveness of tumor behaviour in retinoblastoma and can help in the prediction of its prognosis