Proliferative activity and apoptosis in thymic epithelial neoplasms

Area of Science:

• Oncology
• Pathology
• Molecular Biology

Background:

• Thymic epithelial tumors (TETs) classification is challenging due to difficulties in predicting biological behavior from morphology.
• Understanding proliferative activity and apoptosis is crucial for accurate diagnosis and prognosis of TETs.

Purpose of the Study:

• To evaluate proliferative activity and apoptosis rates in TETs based on World Health Organization (WHO) histological classification.
• To determine the role of proapoptotic factors, including p53 protein and Bcl-2, in TETs.
• To assess the potential of these factors as markers for differentiating thymoma subtypes.

Main Methods:

• Investigated 46 surgically resected TETs across WHO histological types (A, AB, B1, B2, B3, C).
• Utilized immunohistochemical staining to assess tumor expression of p53 protein, Bax, Bcl-2, and survivin.
• Quantified Ki-67 labeling index (LI) for proliferation and apoptotic index (AI) for apoptosis.

Main Results:

• Type C thymoma exhibited significantly higher LI compared to other subtypes. Stage IV thymoma showed higher LI than Stage I.
• Type B1 thymoma displayed a significantly elevated AI.
• Overexpression of p53 protein was noted in Type B3 and C thymomas, correlating with higher LI. Bcl-2 expression was observed in Types A, AB, and C, and was associated with lower AI.

Conclusions:

• Overexpression of p53 protein is linked to increased tumor proliferative activity in thymoma.
• Bcl-2 functions as an apoptosis inhibitor in thymoma.
• Bcl-2 and p53 protein expression levels may serve as valuable biomarkers for distinguishing between different thymoma subtypes.