Abstract

Histologic, immunohistochemical and ultrastructural studies were performed on 6 cases of undifferentiated thyroid carcinoma to study the histogenesis of the undifferentiated thyroid carcinoma, to determine the most useful markers for diagnosing these tumors and to investigate the nature of osteoclast-like giant cells rarely observed in these tumors. For the immuno-histochemical study, a panel of antibodies to epithelial (cocktailed keratin, low molecular weight keratin, CEA), mesenchymal(vimentin, desmin, actin, FVIIIRAg) endocrine(calcitonin, chromogranin), lymphocytic(LCA), histiocytic(alpha-l-ACT, alpha-1-AT, lysozyme, CD68), and Schwann cell(S-100 protein) markers were used. The following results were obtained; 1) Well differentiated carcinoma was associated with 2 cases of spindle cell type and 1 case of giant cell type of undifferentiated thyroid carcinoma and a transitional zone between the well differentiated and undifferentiated lesions was observed. 2) All of the examined cases expressed keratin, and 3 tumors expressed CEA. 3) All the mesenchymal markers, LCA, S-100 protein, calcitonin, and chromogranin were not expressed. Vimentin was coexpressed with keratin in 4 cases. 4) Osteoclast-like giant cells were observed in 1 case of spindle cell type. They expressed CD68 but not keratin. 5) Ultrastructural study revealed the desmosomes between the tumor cells and non-neoplastic, follicular, thyroid epithelial cells. The above results indicate that undifferentiated thyroid carcinoma originates from follicular epithelial cell, keratin is the most useful marker for diagnosis of this tumor, and the osteoclast-like giant cells are histiocytic in nature and reactive, rather than neoplastic.

• Keywords: Thyroid;Undifferentiated carcinoma;Immunohistochemistry;Ultrastructure;