Parathyroid glands
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The parathyroid glands are an endocrine organ that is important in calcium regulation. They often make an appearance in the context of thyroid surgery.
Clinical
Hyperparathyroidism
Classification
- Primary.
- Secondary.
- Tertiary.
Hypercalcemia DDx
Mnemonic GRIMED:[1]
- Granulomatous disease (tuberculosis, sarcoidosis).
- Renal disease.
- Immobility.
- Malignancy (esp. squamous cell carcinoma, plasmacytoma).
- Endocrine (primary hyperparathyroidism, tertiary hyperparathyroidism, familial hypocalciuric hypercalcemia (FHH)).
- Drugs (thiazides ... others).
Note:
- Hyperparathyroidism and FHH are assoc. with an increased PTH.[2]
- Other causes are assoc. with a decreased PTH.
Primary hyperparathyroidism
Cause:[3]
- Parathyroid adenoma ~90%.
- Parathyroid hyperplasia ~10%.
- Parathyroid carcinoma ~1%.
Familial causes of primary hyperparathyroidism:
- MEN 1.
- MEN 2.
- Familial hypocalciuric hypercalcemia.
- Autosomal dominant.
- CASR (calcium sensing receptor) gene defect.[4]
Hypoparathyroidism
- Rare vis-à-vis hyperparathyroidism.
- Classically iatrogenic, i.e. the surgeon removing 'em.[2]
Other causes:[5]
- Autoimmune hypoparathyroidism.
- Autosomal dominat hypoparathyroidism.
- Familial isolated hypoparathyroidism.
- Congenital absence (DiGeorge syndrome).
Normal parathyroid glands
General
- Identification of normal can be tricky.
Gross
- No distinctive features - surgeons thus send 'em to pathologists.
Microscopic
Features:[6]
- Low power:
- May vaguely resemble lymphoid tissue - may have hyperchromatic cytoplasm.
- Does not have follicular centres like a lymph node.
- May form gland-like structure and vaguely resemble the thyroid at low power.
- Cytoplasm may be clear[7] - key feature.
- Surrounded by a thin fibrous capsule.
- May vaguely resemble lymphoid tissue - may have hyperchromatic cytoplasm.
- High power:
| Name | Staining (cytoplasm) | Quantity of cells | Cytoplasm (quantity) | Function |
| (parathyroid) chief cells | intense hyperchromatic to eosinophilic (see note) | abundant | moderate | manufacture PTH |
| oxyphil cells | moderate/light hyperchromatic to eosinophilic | rare | abundant | ? |
Notes:
- Cytoplasmic staining varies considerably on H&E preparations - it may vary from hyperchromatic[10] to clear to eosinophilic[11].
- Chief cells tend to stain more intensely than oxyphil cells.
Thyroid vs. parathyroid (see: parathyroid image):
- Parathyroid cytoplasm:
- Hyperchromatic.
Parathyroid vs. lymphoid tissue (see parathyroid image):
- Parathyroid:
- No germinal centres.
- Gland-like/follicular-like arrangement -- much smaller than normal follicles of
- Occasional cell with rim of clear cytoplasm (oxyphil?).
Images:
Specific entities
Parathyroid hyperplasia
General
- Chief cell hyperplasia - associated with MEN 1, MEN 2A.[12]
- Parathyroid hyperplasia - classically assoc. with renal failure.
- Classically all parathyroid glands are involved; however, some may be spared making it difficult to differentiate this from parathyroid adenoma.[13]
Microscopic
Features:[13]
- Similar to parathyroid adenoma.
- +/-Water-clear cells ("water-clear cell hyperplasia").
Parathyroid adenoma
General
MEN I:
- Parathyroid adenoma.
- Pancreatic neuroendocrine tumours.
- Pituitary adenoma.
MEN IIa/IIb (II/III):
- Parathyroid adenoma.
- Medullary thyroid carcinoma.
- Pheochromocytoma.
Image: Parathyroid adenoma (med.utah.edu).[14]
Microscopic
Chief cell adenoma
Features:[3]
- Chief cells:
- Small central nucleus.
- Moderate cytoplasm.
- +/-Scattered oxyphil cells:
- Large cells.
- Abundant cytoplasm.
Image:
Oxyphil adenoma
Features:[3]
- Oxyphil cells:
- Large cells.
- Abundant cytoplasm.
DDx:
- Hürthle cell adenoma of the thyroid gland.
Parathyroid carcinoma
General
- Extremely rare.
Microscopic
Features:[15]
- Histologically normal parathyroid cells.
- Cytologic features not reliable for diagnosis.
- Fibrous capsule.
- Invasion of surrounding tissue - key feature.
- +/-Metastasis - diagnostic feature.
Note:
- Diagnosis of parathyroid carcinoma is like that of malignant pheochromocytoma - cytology useless, tissue invasion and metastases are the key features.
Image:
See also
References
- ↑ TN06 Emerg.
- ↑ 2.0 2.1 Kumar, Vinay; Abbas, Abul K.; Fausto, Nelson; Aster, Jon (2009). Robbins and Cotran pathologic basis of disease (8th ed.). Elsevier Saunders. pp. 1129. ISBN 978-1416031215.
Cite error: Invalid
<ref>tag; name "Ref_PBoD8_1129" defined multiple times with different content - ↑ 3.0 3.1 3.2 Kumar, Vinay; Abbas, Abul K.; Fausto, Nelson; Aster, Jon (2009). Robbins and Cotran pathologic basis of disease (8th ed.). Elsevier Saunders. pp. 1127. ISBN 978-1416031215.
- ↑ Online 'Mendelian Inheritance in Man' (OMIM) 601199
- ↑ Kumar, Vinay; Abbas, Abul K.; Fausto, Nelson; Aster, Jon (2009). Robbins and Cotran pathologic basis of disease (8th ed.). Elsevier Saunders. pp. 1130. ISBN 978-1416031215.
- ↑ http://www.medicalhistology.us/twiki/pub/Main/ChapterFourteenSlides/b56b_parathyroid_40x_he_labeled.jpg
- ↑ http://pathology.mc.duke.edu/research/Histo_course/parathyroid2.jpg
- ↑ http://www.bu.edu/histology/p/15002loa.htm
- ↑ http://dictionary.reference.com/search?q=oxyphil%20cell
- ↑ http://www.deltagen.com/target/histologyatlas/atlas_files/endocrine/parathyroid_and_thyroid_glands_20x.jpg
- ↑ http://instruction.cvhs.okstate.edu/Histology/HistologyReference/hrendo.htm
- ↑ URL: http://www.pathconsultddx.com/pathCon/diagnosis?pii=S1559-8675%2806%2970475-2. Accessed on: 29 July 2010.
- ↑ 13.0 13.1 Kumar, Vinay; Abbas, Abul K.; Fausto, Nelson; Aster, Jon (2009). Robbins and Cotran pathologic basis of disease (8th ed.). Elsevier Saunders. pp. 1128. ISBN 978-1416031215.
- ↑ URL: http://library.med.utah.edu/WebPath/EXAM/IMGQUIZ/enfrm.html. Accessed on: 6 December 2010.
- ↑ Kumar, Vinay; Abbas, Abul K.; Fausto, Nelson; Aster, Jon (2009). Robbins and Cotran pathologic basis of disease (8th ed.). Elsevier Saunders. pp. 1128. ISBN 978-1416031215.
