Pathology 2: Parathyroid Disorders Flashcards
What is the histology of the parathyroid gland?
Composed mostly of chief cells and oxyphil cells within an adipose stroma.
What do the chief cells look like on H&E stain?
On H&E staining, the chief cells range from light to dark pink and contain secretory granules of parathyroid hormone (PTH).
What do the oxyphil cells look like under the microscope?
Oxyphil cells are slightly larger than the chief cells, have acidophilic cytoplasm, and are tightly packed with mitochondria.
What controls the activity of the parathyroid gland?
Controlled by the level of calcium in the bloodstream.
How does the parathyroid effect calcium?
They decrease levels of free calcium, and stimulate the synthesis and secretion of PTH.
List the 4 effects of PTH?
1- Increase in renal tubular reabsorption of calcium.
2- Increase in urinary phosphate excretion.
3- Increase in the conversion of vitamin D to its active dihydroxy form in the kidneys.
4- Enhancement of osteoclastic activity.
What is the net result of the activities of the PTH?
Increase the level of free calcium, which inhibits further PTH secretion.
List the 3 forms of hyperthyroidism?
1- Primary hyperthyroidism.
2- Secondary hyperthyroidism.
3- Tertiary hyperthyroidism.
Primary hyperthyroidism is a disease of which group?
Disease of adults.
Primary hyperthyroidism is more common in which gender?
More common in women.
List the 3 types of parathyroid lesions causing hyperfunction?
1- Adenoma 75% to 80%.
2- Primary hyperplasia 10% to 15%.
3- Parathyroid carcinoma 1%.
List the 3 genetic syndromes associated with familial primary hyperthyroidism?
1- Multiple endocrine neoplasia - 1 (MEN-1).
2- Multiple endocrine neoplasia - 2 (MEN-2).
3- Familial hypocalciuric hypercalcemia.
List the 3 molecular defects that have a role in pathogenesis of sporadic adenomas?
1- Cyclin D1 gene inversions.
2- MEN1 mutations.
What is the morphology of parathyroid adenomas?
1- Solitary.
2- Averages 0.5 to 5 gm.
3- well-circumscribed, soft, tan to reddish-brown nodule.
4- Surrounded by delicate capsule.
5- The glands outside the adenoma are usually normal in size or shrunken.
6- It is composed of uniform, polugonal chief cells with small, centrally placed nuclei.
7- A rim of compressed, non-neoplastic parathyroid tissue at the edge of the adenoma.
8- Not uncommon to find bizarre and pleomorphic nuclei.
9- Adipose tissue is inconspicuous.
What is the pathogenesis of primary hyperplasia?
It may occur sporadically or as a component of MEN syndrome.
How many glands are involved in primary hyperplasia?
All four glands are involved (asymmetry).
What is the most common microscopic pattern in primary hyperplasia?
The most common microscopic pattern is that of chief cell hyperplasia (diffuse or multinodular).
What other microscopic findings are found in primary hyperplasia?
Stromal fat is not easily seen.
Parathyroid carcinomas usually enlarge how many glands?
One parathyroid gland.
What is the gross findings in parathyroid carcinomas?
Consists of gray-white, irregular masses that sometimes are >10 gm in weight.
What is the microscopic findings in parathyroid carcinomas?
Usually uniform, arranged in nodular or trabecular patterns, with a dense fibrous capsule.
A diagnosis of parathyroid carcinoma is based on what?
1- Invasion of surrounding tissues.
2- Metastasis.
What are the morphologic skeletal changes found in parathyroid carcinoma?
1- Osteoporosis:
- Osteitis fibrosa cystica:
- bone contains widely spaced, delicate trabeuclae.
- the cortex is thinned.
- the marrow contains ( a lot ) of fibrous tissue.
- there are foci of hemorrhage and cyst formation.
- Brown tumors:
- aggregates of osteoclasts, reactive giant cells, and hemorrhagic debris from masses.
What other morphologic changes in other organs are found in parathyroid carcinoma?
PTH-induced hypercalcemia favors the formation of urinary tract stones (nephrolithiasis) as well as calcification of the renal interstitial and tubules (nephrocalcinosis).
