The Use of Immunohistochemical Staining for the Prediction of Wilms Tumour Progression and Recurrence

The Use of Immunohistochemical Staining for the Prediction of Wilms Tumour Progression and Recurrence

P53, Ki67 and Cyclin A Immunohistochemical Staining as Predictors for Wilms' Tumour Aggressiveness and Recurrence

Wilms' tumour staging and grading are used to give an idea about the prognosis. Advanced staging, diffuse anaplasia, predominant blastemal elements and lymph node invasion are indicators of poor prognosis. In spite of using the previously mentioned parameters, some tumours which were considered of low risk did not respond to therapy and eventually resulted in mortality. In contrast, other tumours assumed to be of poor prognosis responded dramatically to treatment. In light of the above, it is crucial to search for predictors of Wilms' tumour prognosis other than tumour staging and grading. Many immunohistochemical (IHC) stains have been studied as prognostic markers for nephroblastoma in literature.

P53 is a tumour suppressor gene, and its mutation is identified in various types of human cancer. P53 protein accumulation in certain tumours is associated with tumour aggressiveness. The role of P53 expression in Wilms' tumour is not clear; however, most studies confirmed its correlation with advanced stages and anaplasia. Ki67 is a nuclear antigen related to cell proliferation, and high Ki67 proliferation index (PI) is accompanied by tumour aggressiveness, distant metastasis and death. Advanced stages and clinical progression of WT were found to be associated with high Ki67 PI. On the other hand, some authors concluded that it may not be a dependable prognostic marker. The cyclin-dependent kinases (CDKs) have a role in transitions between cell cycle phases with the need of cyclins association for their activity. IHC assessment of cell cycle proteins has a diagnostic use in histopathology. Correlation between poor prognosis and overexpression of cyclin A was confirmed in different entities of human cancer such as medulloblastoma and ovarian carcinoma. A recent study deduced that cyclin A overexpression may be associated with the poor prognosis of WT.

P53 staining density and intensity will be calculated. To assess P53 density in a semiquantitative way, a score of 0 will be given assigned if less than 5% of tumour cells expressed p53, 1 if 5% to 50% expressed p53 and 2 if more than 50% stained positive for p53. To evaluate P53 intensity, a score of 0 means weak or absent staining, 1 refers to the intermediate intensity and 2 stands for strong intensity.

Ki67 proliferation index will be used to detect rapidly proliferating cells which means the percentage of positive Ki67 cells over 5 high power fields. It will be semiquantitatively graded as low, moderate, or high and correlated with histological staging.

Regarding Cyclin A, a standard peroxidase-conjugated streptavidin-biotin labelling was used for visualization, with 3,3 diaminobenzidine as chromogen. Level of cyclin A expression will be classified as absent (-), focal (+), moderate (++) diffuse (+++).

P53, Ki67 and Cyclin A immunohistochemical staining of formalin-fixed paraffin-embedded specimens of Wilms' tumour.

Inclusion Criteria: All children presented with Wilms' tumour at the Urology and Nephrology Center, Mansoura University, Mansoura, Egypt from 2000 to 2014. Exclusion Criteria: Preoperative chemotherapy (due to areas of necrosis and haemorrhage hindering immunohistochemical staining). Patients with incomplete follow-up data.