Aim: Thyroid malignancies account for approximately 3% of all human cancers. A loss or reduction in the expression of a tumor suppressor gene, PTEN has been observed in approximately 40% of thyroid tumors. This change in PTEN expression has been shown to be due to PTEN mutation or deletion. The aim of this study was to compare the PTEN expression among Hashimoto thyroiditis, follicular adenomas and malignant tumors originating from thyroid follicle epithelial cells.
Material and Methods: 101 cases of thyroid carcinoma were studied and classified into differentiated types including 15 cases of follicular thyroid carcinomas (FTC), 28 cases of papillary thyroid carcinomas (PTC), 29 cases of follicular adenomas (FA) and 29 cases of Hashimoto thyroiditis (HT). PTEN expression in all the cases were analyzed immunohistochemically.
Results: The cytoplasmic and nuclear staining intensity in Hashimoto thyroiditis showed minimal loss of PTEN expression. The nuclear and cytoplasmic staining intensity and percentage in Hashimoto thyroiditis and follicular adenomas were similar. In most of the papillary carcinoma samples, PTEN expression was lost as deduced from cytoplasmic and nuclear staining intensity. While the loss of nuclear PTEN expression was the highest in follicular carcinoma, the cytoplasmic loss was minimal.
Conclusions: Loss of PTEN expression is more pronounced in papillary and follicular carcinomas than benign lesions. PTEN has been shown to play an oncogenic role in papillary and follicular carcinoma. PTEN expression loss can be used as a new biomarker in PTC and FTC cases.
Key words: Hashimoto Thyroiditis; Follicular Adenom; Papillary Thyroid Carcinoma; Follicular Thyroid Carcinoma; PTEN.
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