Papillary thyroid carcinoma (PTC) is the most common endocrine malignancy in adults, accounting for 80–85% of all thyroid malignancies. The clear cell variant of PTC is rare, representing less than 2% of cases. Histologically, clear cell PTC is characterised by cells forming papillae or solid sheets with clear to granular cytoplasm and will often show typical PTC nuclear features, such as nuclear pseudo inclusions, intranuclear grooves and clearing of nuclear chromatin. Whilst clear cell PTC has a similar prognosis to that of PTC without cell clearing, other entities such as follicular thyroid carcinoma with clear cell features, clear cell medullary thyroid carcinoma, metastatic clear cell renal cell carcinoma or intrathyroidal parathyroid tumours should be excluded. The use of immunohistochemistry is useful to differentiate clear cell PTC from these histological mimics. We describe a case of a clear cell papillary thyroid carcinoma in a 54-year-old woman with a background of Hashimoto thyroiditis with relevant immunohistochemical findings.
McGrath et al. (Sun,) studied this question.