Endocrine Abstracts

Background: Parafibromin is an ubiquitously expressed protein and a member of the polymerase-associated factor 1 complex associated with RNA polymerase II, which regulates transcription elongation, histone modification and cell proliferation. It is encoded by the CDC73 gene also known as the HRPT2 gene. Endogenous parafibromin inhibits expression of MYC gene that encodes the c-Myc proto-oncogene. Parafibromin has three nuclear localization signals, and mutation of this region blocks nuclear targeting. Overexpression of WT can induce apoptosis in transfected cells. The pathological distinction between parathyroid neoplasms and hyperplasias remains difficult in several cases. Parafibromin can be useful in differential diagnosis of parathyroid carcinoma from adenoma and may be a prognostic marker.

Aim: The aim of the study was to examine whether immunohistochemical expression of parafibromin may be useful in distinguishing between parathyroid hyperplasia and neoplasia.

Methods: Tissue specimens were taken from patients with primary hyperparathyroidism due to adenoma, hyperplasia and carcinoma. Normal glands served as controls. In a standard immunohistochemical procedure, MABs to parafibromin from Santa Cruz Biotechnology were applied. The dilution of the primary antibodies was 1:500 and was verified in a series of pilot experiments. The immunohistological investigations were performed by the BrightVision method from ImmunoLogic. The sections were counterstained with Mayer’s haematoxylin.

Results: Parafibromin was underexpressed in parathyroid carcinoma compared to adenoma, whereas the amount of positively-stained cells in adenoma was lower than in healthy parathyroid tissue.

Conclusion: Parafibromin can be useful in differential diagnosis of parathyroid carcinoma, adenoma and hyperplasia, and may be a prognostic marker.