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Parathyroid gland

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IntroductionEdit

Parathyroid glands or portions thereof are removed surgically in patients with hyperparathyroidism. Sometimes the removal is subtotal (e.g., “10% of right lower parathyroid”); in these cases the surgeon is trying to avoid a total parathyroidectomy in case s/he has not found the adenoma. Alternatively, s/he may be saving some to implant in the patient’s arm.

The questions to be answered in primary hyperparathyroidism are:

  • Is this parathyroid tissue?
  • Does it have features of hyperfunction? (Increased cellularity, decreased intracellular fat, rim of normal parathyroid.) These occur in both adenomas and hyperplasia.
  • Is this lesion involving one gland or multiple glands?

The question to be answered in secondary hyperparathyroidism is:

  • Is the tissue sent from all four regions of suspected parathyroid tissue truly parathyroid?

Occasionally parathyroid tissue is removed incidentally in the course of an operation for some other neck disease; in these cases, identification of the tissue as parathyroid is required as well as laterality and site.


Fresh HandlingEdit

  1. Usually, frozen section will be requested.
  2. Measure the specimen and weigh it on the microgram balance.
  3. If specimen is large, may need to bisect. Describe bisection, and whether a rim of "normal" parathyroid is grossly seen.
  4. Freeze entire specimen if small.
  5. If too large to be frozen without bisecting, you can submit half of the specimen. (If it is an adenoma, there will be adenoma in both halves.)
  6. A small portion of the remaining specimen can be taken for tissue banking.
  7. Cut five frozen levels. Two are stained by H&E, one is stained by toluidine blue, and two are sent to the histology lab for oil red O staining.

Toluidine Blue StainingEdit

  1. Fix frozen section in methanol. (Fixation is essentially instantaneous.)
  2. One minute in toluidine blue solution.
  3. Dip once or twice in water to destain.
  4. Cover with a coverslip without mounting medium. (The medium is nonpolar so it will cloud up if it comes into contact with water.)


Grossing InEdit

  1. Submit in toto.
  2. Try to find the hilum grossly, since that is where the rim of normal parathyroid is often found in patients with adenomas. Submit so that the hilum will be seen in the section.
  3. If the specimen weighs >5.0 grams, consult your attending.


Review and SignoutEdit

Uniquely, parathyroid diagnoses are not usually stated outright for each specimen; the diagnosis line for these specimens is descriptive and the case is interpreted as a whole in the comment. Sample diagnostic lines:

  • “Normocellular parathyroid with retained intracellular fat”: Probably normal parathyroid.
  • “Hypercellular parathyroid with decreased/absent intracellular fat”: Probably a parathyroid adenoma. These specimens often have a rim of normal parathyroid in them.
  • “Normocellular parathyroid with decreased intracellular fat” or ”Hypercellular parathyroid with retained intracellular fat”: Ambiguous scenarios that may or may not represent an adenoma.

Use the clinical picture, histology, and intraoperative PTH levels to figure out what is happening with the patient.

Common scenarios:

  • Primary hyperparathyroidism with single adenoma
    • All of the specimens are normal except for one that is large and looks like an adenoma. After the adenoma was removed, the intraoperative PTH fell by at least 50% and reached the normal range.
  • Primary hyperparathyroidism with multi-gland disease
    • There is a specimen that is large and looks like an adenoma, but the PTH did not fall into the normal range after it was removed. A subsequent specimen also looks like an adenoma and the PTH did reach the normal range after it was removed. Write a note that explains the situation. This scenario is usually due to gland hyperplasia, since double adenomas are rare (~3% in tertiary care setting).
  • Secondary hyperparathyroidism
    • The patient has end-stage renal disease and possibly renal osteodystrophy. Four enlarged hypercellular glands that can show diffuse or nodular proliferation are submitted. There is no rim (vs adenomas, which do show a rim), even though one of the glands may be markedly enlarged and show fibrosis. Write a note stating that the findings would be consistent with secondary hyperparathyroidism.
    • Note: Carcinomas arising in a background of hyperplasia due to renal disease are reportable!
  • Parathyroid carcinoma
    • These are rare but do occur. Look for invasion into soft tissue and surrounding structures, vascular invasion, thick fibrous bands and mitotic activity.
    • Parafibromin stain (lost in parathyroid carcinoma) may be helpful to make this diagnosis.


ReferencesEdit

Intraoperative PTH monitoring: Fraker DL, Harsono H, Lewis R. World J. Surg. 33(11) 2256–65 (2009).


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