Parathyroid
Carcinoma
Epidemiology and Etiology:
- <1% of
primary hyperparathyroidism
- M=F
- All ages from early
childhood
- Risk factors:
- Secondary parathyroid
hyperplasia
- Neck irradiation
- Thought to arise de
novo rather than from pre-existing adenoma
Common Sites:
- Anwhere parathyroid
can be found
Gross features:
- solitary
- firm
- gray-white
- irregular
- adherent to
adjacent structures often
- sometimes exceed
10g
- palpable neck mass
(75%) (unusual in adenomas)
- necrosis
(occasionally)
- mets:
- cervical and
mediastinal lymph nodes
- lungs
- bone (distinguish
from benign “brown tumours” of severe hyperparathyroidism and ossifyuing
fibromas of hyperparathyroidism-jaw tumour syndrome)
- liver
Histologic features:
- invasion of
surrounding tissues or metastasis (ONLY DIAGNOSTIC CRITERIA)
- lymphovascular
invasion is unequivocal (within capsule or outside lesion only)
- perineural space
invasion
- capsular
penetration with growth into adjacent tissues
- note that
parathyroid hyperplasia can “invade” surrounding tissues
- mets
- note seeding from
an intraoperatively ruptured adenoma or hyperplastic gland occasionally
causes implatns mimicking malignant growth
- triad of high risk
of malignancy (if all 3 are present):
- coagulative
necrosis is worrisome
- variable mitotic
activity (not helpful) – but > 5 mitoses per 50 HPF is worrisome
- macronucleoli are
worrisome
- uniform cells
resembling normal parathyroid cells
- may be
predominantly chief cells (usually) or predominantly oxyphil cells
- arranged in nodular
or trabecular patterns
- nuclear
pleomorphism is not helpful
Immunophenotype:
Marker:
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Sensitivity:
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Specificity:
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Molecular features:
- HRPT2 mutations
- cytogenetics:
- 13q loss has been
reported
- rarely 11q loss
(MEN1 gene) (frequently lost in adenoma)
- familial (some):
- hyperparathyroidism-jaw
tumour syndrome
- (inactivating HRPT2
mutation)
- NOT thought to be
associated with MEN 1
Other features:
- secretion of PTH
- severe
hypercalcemia often, with associated symptoms
- recurrent laryngeal
nerve palsy in a patient with primary hyperparathyroidism
- palpable neck mass
(75%) (unusual in adenomas)
- 5y survival 40-85%
- 10y survival 50%
References:
- Robbins &
Cotran Pathologic Basis of Disease (2005)
- WHO Tumours of
Endocrine Organs (2004)