Primary Squamous Cell Carcinoma of the Thyroid Diagnosed as Anaplastic Carcinoma: Failure in Fine-Needle Aspiration Cytology?
(a) Thyroid adjacent to the tumor with morphological appearance of Hashimoto’s thyroiditis; follicles are surrounded by lymphoplasmacytic inflammatory infiltrate (40x, hematoxylin and eosin (HE)). (b) Fibrotic bands and inflammatory infiltrate (40x, HE). (c) Moderately differentiated squamous cell carcinoma (grade II) infiltrating the stroma of the thyroid (20x, HE). (d) Interface between squamous cell carcinoma and inflammatory stroma (40x, HE). ((e) and (f)) Squamous cell carcinoma showing cellular pleomorphism, bizarre nuclei, and keratinization of individual cells (1000x, HE).