The Role of Parafibromin, Galectin-3, HBME-1, 
and Ki-67 in the Differential Diagnosis of Parathyroid Tumors.

OBJECTIVES Parathyroid carcinoma (PC) is a rare parathyroid tumor compared to parathyroid adenoma (PA) and atypical parathyroid adenoma (APA). Recent studies have suggested parafibromin has a role in the differential diagnosis of parathyroid tumors. We sought to determine the role of parafibromin as well as galectin-3, Ki-67, and HBME-1 as diagnostic markers in the differential diagnosis of parathyroid tumors. METHODS A total of 92 cases diagnosed with PA, APA, or PC at Sifa University and Private Ege Pathology Laboratory between 2006-2012 were included in the study. Parafibromin (microarray), galectin-3, Ki-67, and HBME-1 were evaluated using immunohistochemistry in all parathyroid tumors. RESULTS Eighty-four cases were diagnosed with PA, six with APA, and two with PC. The study group consisted of 82 females and 10 males. Their mean age was 50.9 years, and the mean tumor diameter was 1.97 cm. Parafibromin was negative in the two PC cases but positive in all APA and PA cases. Positivity was observed with galectin-3 in 17 adenoma cases, three atypical adenomas, and two carcinoma cases. Positivity with HBME-1 was found in 26 PA cases and one PC case. Parafibromin and galectin-3 expression was significant between the three tumor groups but not for HBME-1 expression. Parafibromin expression increased in PA whereas galectin-3 expression decreased. A statistical significance was found between the three tumor groups according to the Ki-67 score (p=0.010). Additionally, the Ki-67 proliferation index was under 1% in PAs. CONCLUSION The number of PCs in our series was small so our data mostly reflects the immunohistochemical characteristics of PAs. Parafibromin expression, galectin-3 negativity, and a Ki-67 proliferation index under 1% were estimated as beneficial in the differential diagnosis of difficult parathyroid tumors.