Primary hyperparathyroidism is the clinical result of parathyroid adenoma or hyperplasia, rarely of carcinoma. Clinical, serologic, and radiologic data are unable to discriminate a single parathyroid adenoma from an enlarged hyperplastic gland. Morphologic features also overlap in adenoma and small hyperplastic gland. Studying immunohistochemical expression of fatty acid synthase (FAS), p53, Ki67 and bcl-2, we found that among 21 adenomas 19 (90.5%) were positive for FAS, 12 (57.2%) for Ki67, 11 (52.4%) for p53, and 16 (76.2%) for bcl-2; among 12 hyperplasias, 12 (100%) were positive for FAS, 6 (50%) for KI67, 8 (66.7%) for p53, and 8 (66.7%) for bcl-2. Statistical analysis showed that FAS was associated with parathormone (PTH) (P =.001), Ki67 (P =.01), and p53 (P =.01). Moreover, FAS was associated with hyperplastic (P =.0001) and adenomatous glands (P =.0001). Ki67 was associated with both adenomatous (P =.02) and hyperplastic glands (P =.005). P53 protein were associated only with hyperplastic glands (P =.01). The different occurrence of p53 in parathyroids adenoma and hyperplasia may enable a different management and follow-up of the patients with primary hyperparathyroidism, stratifing them into two groups. The first, with a "false" adenoma having a high risk of relapse, may necessitate exams like serum calcium levels, PTH concentrations, urinary calcium levels for 24 hours, kidney functional tests, and radiology and ultrasound every 3 to 6 months, whereas the second with "true" adenoma, at low risk of relapse, may be checked less frequently with serum calcium levels and PTH concentrations.
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