Ultrastructure of human parathyroid cells in health and disease

Abstract

Parathyroid glands (n = 271) removed from 130 patients were examined by light and electron microscopy. A standardized method of tissue processing was employed and morphometry was performed. The aim of the paper is to provide a description of the human parathyroid chief cell ultrastructure in health and disease, with quantitative evaluation of structures involved in secretion of parathyroid hormone in a large case series, and to discuss their role in current diagnostic histopathology. The patients were euparathyroid (n = 10), or affected by primary (n = 97), secondary (n = 8), or tertiary (n = 15) hyperparathyroidism. In normal glands, solid parenchyma was composed of chief cells, large clear cells, transitional-oxyphil cells, and oxyphil cells. Chief cell hyperplasia, pseudo-adenomatous hyperplasia, adenoma, water-clear cell hyperplasia, and carcinoma were the most usual forms of parathyroid disease responsible for primary hyperparathyroidism. In chief cell hyperplasia, all the parathyroid glands were enlarged and the chief cells were in an active state of hormone secretion, with a large Golgi complex, abundant rough endoplasmic reticulum (RER), small lipid droplets, and tortuous plasma membrane. In pseudo-adenomatous hyperplasia, one gland was enlarged and the others displayed a normal size; however, electron microscopic examination and morphometric analysis showed that all the glands had active cells. Adenomas displayed a pattern similar to those of pseudo-adenomatous hyperplasia, with one gland enlarged and the others of normal size. However, ultrastructural examination and morphometry showed that the normal-size glands were hypo-active. Water-clear cell hyperplasia showed cells filled with cytoplasmic vacuoles. In these cells, structures with intermediate features between secretory granules and vacuoles were visible. Nucleo-cytoplasmic atypias were frequently visible in parathyroid carcinoma cells. In secondary and tertiary hyperplasia, active chief cells were regularly mixed with oxyphil or transitional-oxyphil cells. The tertiary hyperplasia was characterized by RER-associated structures that were not found in the normal or other pathological conditions. These results demonstrate that electron microscopy and morphometry represent useful tools in parathyroid histopathology.

An Update on the Structure of the Parathyroid Gland

“…Oxyphil cells have been shown histochemically to have a higher oxidative and hydrolytic enzyme activity than chief cells associated with the marked increase in mitochondria. Transitional oxyphil cells between the chief cells and oxyphil cells are observed in the parathyroid gland [5,6,31]. Both transitional and oxyphil cells are not altered in response to either short-term hypocalcemia or hypercalcemia in animals, but they may be increased in response to long-term stimulation of human parathyroid glands.…”

Functional and genetic studies of isolated cells from parathyroid tumors reveal the complex pathogenesis of parathyroid neoplasia

“…Based upon size and morphology, P3 cells were provisionally identified as peripheral blood lymphocytes. P4 cells displayed highly interdigitated plasma membranes, sparse mitochondria, and prominent intracellular secretory granules, all features of parathyroid chief cells (18). P5 cells were large and contained round nuclei, moderate peripheral chromatin condensation, and numerous mitochondria densely packed throughout the cytoplasm.…”

Morphology of Healthy Human Parathyroid Glands in Cytologic Smears

“…These cell types are described in histologic, light microscopic and electron microscopic preparations of normal glands with normal morphology and function. [11][12][13][14] Moreover, data on the morphology of the 4 cell types in smears of healthy HPGs and a comparison with the morphology of the same parenchymal cells in histologic sections are also absent.…”

“…These morphologic cell types are described for light microscopic, histologic and electron microscopic preparations of normal HPGs. [11][12][13][14] Also, cytologic-histologic correlation of the cell types in healthy HPGs, as well as systematic morphometric analysis of the nuclei of these cells in smears, is missing. Further, the ratio of representation of different cell types in smears of the glands without altered function has not been established.…”