COMPARISON OF PROLIFERATIVE ACTIVITY IN PARATHYROID GLANDS IN PRIMARY AND SECONDARY HYPERPARATHYROIDISM.

Objective. Parathyroid gland hyperplasia is diffuse or nodular in secondary hyperparathyroidism (sHPT) in patients with renal failure. Whether the nodular growth starts from the beginning or is the transformation of a diffusely-growing gland into nodular hyperplasia in parallel with increases in the severity of the disease is unknown. The disease might be unresponsive to medical treatment when nodular hyperplasia develops. This study aims to differentiate the characteristics of the parathyroid glands with and without nodular hyperplasia in sHPT, and to investigate if there is any similarity between the nodular hyperplastic glands of sHPT and the parathyroid adenomas of primary hyperparathyroidism. Materials and Methods. Hyperplasia types (nodular or diffuse) and parathyroid cell types, and the expression of proliferating cell nuclear antigen (PCNA) and Ki-67 in parathyroid tissue were investigated histopathologically and immunohistochemically in 94 parathyroid glands of 42 patients with hyperparathyroidism. Results and Discussion. 63 glands showed nodular hyperplasia and 16 diffuse hyperplasia in sHPT. Chief cells predominated across the whole series. Vacuolated chief cells most frequently accompanied chief cells in both nodular hyperplasia (28.6%) and adenomas (53%). The median ratio of PCNA LI (labelling index) was 30/10³ (min: 4-max: 720) cells in nodular hyperplasia, 16/10³ (min: 2-max: 180) cells in diffuse hyperplasia and 30/10³ (min: 10-max: 707) cells in adenomas (p>0.05). The highest PCNA LI according to all the cell types in the series was in chief cell and vacuolated chief cell combinations (53/10³, p=0.04). These findings suggest that parathyroid adenoma and nodular hyperplasia have histopathologically- and immunohistochemically-similar characteristics suggesting that both have aggressive cell proliferation. [ABSTRACT FROM AUTHOR]