Parathyroid gland - Parathyroid adenoma

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Parathyroid gland

Neoplasms

Parathyroid adenoma

Reviewer: Monika Roychowdhury, M.D. (see Reviewers page)
Revised: 17 February 2013, last major update January 2013
Copyright: (c) 2003-2013, PathologyOutlines.com, Inc.

General
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● Usually monoclonal, but hyperplastic glands may also be monoclonal
● Difficult to diagnose - best criterion is lack of hypercalcemia for 5 years after excision
● Remaining glands usually normal in size or shrunken due to feedback inhibition from elevated serum calcium (presence of microscopically normal second gland strongly suggests that parathyroid lesion is an adenoma); 10% of patients show minimal hyperplasia in remaining glands

Epidemiology
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● Demographics: 75% women, usually in 30’s, solitary lesions, functionally active, clonal

Clinical features
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● May deform esophagus or trachea
● 10% in mediastinum, behind thyroid gland, within thyroid gland (Mod Pathol 1989;2:652), or other abnormal sites
● Double adenomas very rare (< 1%, Arch Pathol Lab Med 2001;125:178)
● Mitotic activity does not predict behavior (Am J Clin Pathol 1981;75:345)

Case reports
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● 42 year old man with back pain (Arch Pathol Lab Med 2002;126:1541)
● 48 year old man with 11 year history of chronic renal insufficiency (Ann Thorac Cardiovasc Surg. 2012 Nov 30. [Epub ahead of print])
● 67 year old woman with primary hyperparathyroidism (Arch Pathol Lab Med 1996;120:883)
● 67 year old woman with papillary adenoma (Arch Pathol Lab Med 1996;120:883)
● 68 year old woman with primary hyperparathyroidism (Int J Surg Case Rep 2013;4:105)
● Rare ectopic parathyroid adenomas near/in esophagus (Arch Pathol Lab Med 1978;102:242)
● Case with papillae formation (Arch Pathol Lab Med 1988;112:99)

Clinical images
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Various images of parathyroid gland and adenoma

Gross description
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● Solitary, 0.5 to 5.0 g, well circumscribed tan nodule with delicate capsule
● May undergo cystic change or hemorrhage
● May have rim of normal tissue

Gross images
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Various images

Figure C: red-brown mass within the cystic lesion

Various images contributed by Dr. Mona Kandil, Menoufiya University, Egypt

Right: parathyroid adenoma; left: thymoma

Micro description
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● Encapsulated, cellular, homogenous lesions, rarely papillary, composed of chief cells with some oxyphil cells in delicate capillary network
● Microfollicles resembling those in thyroid are common
● May see rim of compressed normal tissue if adenoma is very large
● Adipose tissue is rare (Am J Surg Pathol 1988;12:282)
● Minimal mitotic activity
● May see clusters of bizarre nuclei (also seen in other benign endocrine tumors)
● Large tumors often display hemorrhage, cholesterol clefts, fibrosis
● Usually no capsular invasion, no vascular invasion, no invasion of adjacent tissue

Micro images
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Figure B: FNA shows elongated nuclei and nuclear groove; D: histologic section

Adenoma with rim of normal parathyroid tissue and small benign parathyroid cyst

Rim of normal parathyroid tissue admixed with adipose tissue cells compressed to lower edge of adenoma

Various images contributed by Dr. Mona Kandil, Menoufiya University, Egypt

Positive stains
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● Parathyroid hormone, glycogen, keratin, cyclin D1 (40%, Mod Pathol 1999;12:412), neurofilament, renal cell carcinoma marker (Am J Surg Pathol 2001;25:1485)

Negative stains
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● TTF-1 (Am J Surg Pathol 2001;25:815)

Electron microscopy description
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● Long cytoplasmic processes (microvilli) extending into wide intercellular spaces are associated with high serum calcium (17.5 mg/dl) vs. relatively straight plasmalemma with interdigitations and narrow intercellular spaces, associated with moderately elevated calcium (mean 12.4 mg/dl)
● High serum calcium case also had numerous nuclear pores and annulate lamellae but inconspicuous Golgi apparatus (Hum Pathol 1985;16:511)

Molecular description
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● Loss of heterozygosity in 1p (Mod Pathol 2001;14:273)

Differential diagnosis
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● Papillary adenomas resemble papillary carcinoma of thyroid (Arch Pathol Lab Med 1996;120:883)

End of Parathyroid gland > Neoplasms > Parathyroid adenoma

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