Primary Squamous Cell Carcinoma of the Thyroid Diagnosed as Anaplastic Carcinoma: Failure in Fine-Needle Aspiration Cytology?

Figure 2

Immunohistochemical staining (IHC) evaluation of the tumor. (a) AE1/AE3: positive and diffuse cytoplasmic immunoexpression (400x); (b) p63: positive and diffuse nuclear immunoexpression (400x); (c) Ki-67: high cell proliferation index (approximately 70%) (400x); (d) thyroglobulin, TTF-1, CEA, and calcitonin: negative immunoexpression (400x).

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