Objective: The present study was designed to prove the existence of apoptosis in retinoblastoma (Rb) and to determine the pathogenic mechanism of spontaneous regression of Rb as well as the relationship between them.
Methods: Qualitative morphological study on Rb was performed by means of light microscope, electron microscope and TdT mediated biotin-dUTP nick-end labeling (TUNEL). Quantitative study was performed by automatic image analysis technology (AIAT) stained with Feulgen reaction.
Results: The characteristic regressed area occurred in all 47 cases of Rb. Morphological changes observed within Rb closely resembled the apoptotic cell described by Kerr et al in 1972. Under electron microscope, details of apoptosis were observed in 7 cases of Rb: the morphological sequence of events occurred in and around the cell nucleus. The morphology of the TUNEL labeling Rb cell was various. TUNEL labeling showed more positive cells in regressed area, while fewer in advanced area. AIAT revealed that apoptosis index (AI) in regressed areas was higher than that in other areas of Rb, DNA average ploidy (DP) consisted with the histology grade of Rb, the degree of hyperdiploid (DH) in metastatic area was distinctly higher than that in other areas (P < 0.05). CONCLUSIONS 1. Morphologic evidence proved the existence of apoptosis, especially more in regressed area of Rb. 2. Apoptosis may participate in the spontaneous regression of Rb. Apoptosis contributed to the spontaneous regression of Rb. 3. Tumor growth parameters of Rb (AI, DP, DH) obtained by AIAT may be used as quantitative index for pathologic classification, the selection of clinical treatment and the prognostic evaluation.