A Rare Entity of Papillary Carcinoma of Thyroid with Squamous Cell Carinoma Component: Case Report

While squamous metaplasia is a well-known phenomenon in papillary thyroid carcinoma (PTC), diagnosing a PTC with squamous differentiation (PTC-SD), especially in a young patient, is extremely rare, thereby posing a diagnostic challenge given its broad histopathological differential diagnosis. We present a rare case of PTC-SD diagnosed in a solitary thyroid nodule (STN) in a 45-year-old man with a family history of thyroid cancer. Indeed, detection of the squamous cell carcinoma component might not be feasible by fine-needle aspiration cytology or frozen sections, whereas permanent paraffin sections and immunohistochemistry (if necessary) usually allow its identification. Due to their diverse clinical and biological behaviors, it is important to differentiate PTC-SD from other conditions in which a thyroid specimen contains squamous epithelium.