Endocrine Abstracts (2006) 11 P803

Parathyroid hormone determination in fine needle aspirates (PTH-FNAB) allows the differentiation between thyroid and parathyroid lesions

V Triggiani, E Guastamacchia, F Resta, C Sabba’ & E Tafaro

University of Bari, Bari, Italy.

Parathyroid lesions are often occasionally discovered during thyroid ultrasound evaluation (incidentalomas); in other cases there is a previous diagnosis of hyperparathyroidism. In many cases it is difficult or even impossible to distinguish these lesions from those of thyroid origin, because they often share common ultrasound features. Scintiscan and cytology are also frequently inadequate. The aim of this study is to evaluate the contribute of PTH determination in the aspirates. 46 patients (37 female and 9 male, age 54.1±12.6, range 24–83 yrs) out of 1,870 consecutive patients with neck nodular lesions submitted to FNAB in three years by the same physician (first author) were suspected to have one or more nodule(s) of parathyroid origin. The ultrasound examination of the neck of these patients, in fact, showed one or more nodules placed in the posterior aspect of thyroid lobes. Furthermore, 13 of these patients showed a laboratory findings suggestive for primary hyperparathyroidism, 6 of which with clinical evidence. The nodules were submitted to ultrasound-guided-FNAB. For 55 lesions suspected to be of parathyroid pertinence, the needle used to perform the aspirate was then washed using 1 ml of normal saline and PTH determination (immunoradiometric assay) on the fluid obtained was done. In case of cystic lesions, PTH determination was performed directly in the liquid aspirated.

Results: The shape of the nodules suspected to be of parathyroid pertinence was round in 24 cases and oval in 31 cases. The echo-pattern was hypoechoic in 43 (78%) cases, isoechoic in 3 cases, cystic in 8 cases and mixed in 1 case. The range of volume was 0.7–33.4 ml. In 6 cases a water-clear liquid was obtained from the aspiration of cystic nodules, suggesting a parathyroid origin. In these cases the cytological examination lead to a non-diagnostic result due to the scant number of cells. The aspiration of solid lesions gave sufficient material but cytology did not lead to a clear distinction. The results of PTH determination in the needle washings ranged from 6.7 to 16640 pg/ml. 16 patients underwent surgical intervention: histological examination of the 23 lesions submitted to PTH-FNAB showed 7 thyroid nodules, 11 parathyroid adenomas and 5 hyperplasic parathyroid lesions. In one case the lesions aspirated (low PTH in the aspirates) resulted thyroid nodules at histology, but a parathyroid adenoma in ectopic location was found. There was a strong positive correlation (P<0.0005) between high levels of PTH-FNAB (more than 190 pg/ml) and the histological finding of parathyroid lesions. PTH-FNAB was also high in 4 out of 6 water-clear liquid containing cysts.

Conclusions: PTH-FNAB can be considered the gold standard for verification of parathyroid tissue.

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