Week 4: pathology of parathyroid glands

Question 1

normal parathyroid glands

Answer 1

~5mm in diameter

• inferior are from 3rd pharyngeal arch and migrate with the thymus in embryology
• superior two are from 4th pharyngeal arch

Question 2

Cell types of parathyroid glands

Answer 2

1. Chief cells: main functional cell
2. Oxyphil cells: larger, with numerous mitochondria. granular appearance
3. water-clear cells: cytoplasm appears to by empty by H and E (glycogen)
4. transitional cells: evidence that water clear and oxyphil cells are from chief cells
5. Adipocytes: increases with age and are diminished in hyperplasia

Question 3

Genesis of parathyroid glands

Answer 3

• congenital absence
• chromosome 22
• DiGeorge syndrome: agenesis of parathyroids and thymus
• CATCH22: cleft palate, appearance, thymus/immunology deficiency, calcium salt low, heart defect

Question 4

Ectopic parathyroid

Answer 4

• inferior parathyroids may migrate with thymus and be found in the lower neck on in the mediastinum with the thymus
• glands could also be within thyroid, in carotid bifurcation, pericardial cavity

Question 5

Parathyroid cysts

Answer 5

small tubules that are associated with parathyroids that persist can develop cysts
-aspirate clear fluid vs thyroid cyst which would have blood/colloid in cyst

Question 6

Primary hyperplasia of parathyroid glands

Answer 6

• all four glands are enlarged
• cause: adenoma, primary hyperPTH, MEN syndromes
• microscopic: hyperplasia usually involves chief cells. Lobulated appearance. Diminished fat cells

Question 7

Secondary hyperplasia of parathyroid glands

Answer 7

• all four gland enlarged
• gross: paler than brown hue in primary hyperplasia
• causes: chronic renal disease most common, hypocalcemia, hyperphosphatemia, Vitamin D deficiency
• can occur as a compensatory enlargement of parathyroids in conditions that tend to lower blood Ca or raise phosphorus

Question 8

Tertiary hyperparathyroidsm

Answer 8

• development of autonomous parathyroid hyper function in a person with secondary hyperPTH, not under influence of Ca
• gland continues to hyper function even after stimulus is removed
• cause: adenomas, carcinomas
• pathogenesis obscure

Question 9

Parathyroid adenoma

Answer 9

• most common cause of primary hyperPTH (80-90%)
• single enlarged gland
• microscopic: rim of residual parathyroid tissue around adenoma
• predominant cells: chief cells or water-clear cells or mixture
• fat cells not really present in adenoma
• can do Sestamibi scan

Question 10

Parathyroid carcinoma

Answer 10

• rare
• difficult to diagnose: palpable mass in neck, extreme high serum calcium higher than 15mg/dl, difficult resection
• infiltrative growth
• high mitotic rate
• vascular invasion, capsular invasion, metastasis
• trabecular growth, thick fibrous septae

Question 11

Manifestations of hyperPTH

Answer 11

• Calcification of kidneys, soft tissues, renal stones
• Peptic ulcer disease
• Pancreatitis
• Osteitis fibrosa cystica (Brown tumor of bone)

Question 12

Bone lesions in hyperPTH

Answer 12

• skull: salt and pepper apperance
• vertebrae: demineralization. Look like Rugger-jersey
• digits: erosion, resorption
• spine fractures: compression fracture, kyphosis
• bone: soap bubble appearance-osteitis fibrosa cystica- with cystic and hemorrhagic spaces and hemosiderin deposition that gives it brown appearance

Question 13

osteitis fibrosa cystica

Answer 13

• resorption of bone, replacement of marrow spaces and resorbed bone by fibrous tissue, and attempts at repair with rows of osteoblasts covering newly deposited layers
• multinucleated giant cells
• hemorrhage
• hemosiderophages

Question 14

hypercalcemia of malignancy

Answer 14

• squamous cell carcinoma: releases PTHrP
• renal cell carcinoma
• ovarian tumors
• bladder tumors