Thymoma is a primary tumor of the thymus epithelial cells. It may be asymptomatic or accompanied with atypical clinical symptoms or paraneoplastic syndromes, such as myasthenia gravis. The biological behavior of thymomas is unpredictable. The invasion of the capsule or the adjacent tissues is the major diagnostic criterion for the malignant behavior of these tumors. This is an interesting case of thymoma diagnosed by fine-needle aspiration biopsy (FNA) and ThinPrep technique, in a 54-year-old female patient with a history of gastric adenocarcinoma. Cytology of the mediastinum mass revealed a mixed population of epithelial cells and lymphocytes. The tumor was excised and the histopathological examination supported the cytological diagnosis. Thymomas commonly constitute a problem in differential diagnosis of mediastinum masses. FNA biopsy in correlation with ThinPrep technique and immunocytochemistry may play a significant role in clarifying the nature of these lesions and may contribute to the early management and choice of the optimal therapeutic manipulation.

BACKGROUND: CD44 is a polymorphic family of cell surface proteoglycans and glycoproteins implicated in cell-to-cell and cell-to-matrix adhesion interactions and tumor metastasis. Its expression appears to be an indicator of invasive and metastatic behavior in carcinomas. The purpose of our study is to investigate the immunohistochemical expression of CD44 protein in thyroid lesions and its association to other histopathological parameters. METHODS: Samples from thyroid lesions were obtained from 40 patients treated in our hospital. The material consisted of 5 cases of multinodular goiter, 7 cases of thyroiditis (Hashimoto type), 5 cases of follicular adenoma, 4 cases of Hurthle cell tumor, 15 cases of thyroid carcinoma (11 papillary carcinomas, and 4 myeloid tumors), and 4 cases of normal thyroid tissue. Immunostaining was performed using the Ventana ES automated immunostainer. A monoclonal antibody was used and avidin-biotin method was applied to paraffin-embedded samples. A membranous immunostaining pattern was considered positive. RESULTS: CD44 expression was detected in three adenomas (60%), mostly of follicular type, and in eight carcinomas (72%). The CD44 immunostaining was especially apparent in papillary type of carcinomas which showed high expression. In normal thyroid tissue, a reduced CD44 expression was observed. CONCLUSION: The results of our study indicate that deregulated expression of CD44 contributes to the ability of thyroid carcinomas for invasion and metastasis and may constitute a prognostic factor for malignant biological behavior