Thyroid carcinoma is the most common endocrine malignancy and 80% of all thyroid malignancies are papillary thyroid carcinoma. The diagnosis of papillary thyroid carcinoma is based on architectural features combined with nuclear features, including nuclear clearing, overlapping, grooves and pseudo inclusions. It is always challenging in our everyday practice to distinguish folicualr variant papillary thyroid carcinoma (FVPTC), one of the subtypes of PTC, from cellular adenomatous nodules. Nuclear clearing in benign thyroid lesion, such as in Hashimoto’s disease may lead pathologists to misdiagnose papillary thyroid carcinoma. In an unusual condition, it may also be difficult for differentiating papillary hyperplastic nodules from papillary thyroid carcinoma.

HBME1 is a monoclonal antibody which was originally developed as a mesothelioma marker and directed against the microvillous surface of mesothelial cells. Subsequently, it was applied to the diagnosis of malignant thyroid conditions. Several studies demonstrated that HBME-1 is a sensitive marker for papillary thyroid carcinoma.

Calcification of thyroid carcinoma and benign thyroid lesions are common. In practice, decalcification process must be performed for surgical pathological slides formation to evaluate the nature of the calcified lesion. Decalcification has been demonstrated to affect the identification of markers by immunohistochemistry. More importantly, nuclei of thyroid follicular cells close to calcified areas can appear to have (?) nuclear clearing or even nuclear grooves. As an important marker for diagnosing PTC, the effect of decalcification in HBME-1 staining for papillary thyroid carcinoma has not been elucidated. For this purpose, we performed immnuhistochemical stains for HBME-1 in calcified PTCs by using calcified benign thyroid lesions as controls and concluded that decalcification does not affect HBME-1 stain for PTCs.