Parathyroid hormone assay in fine-needle aspirate is useful in differentiating inadvertently sampled parathyroid tissue from thyroid lesions

To assess the utility of chemical analysis for parathyroid hormone in the rinse (PTH-r) obtained via fine-needle aspiration (FNA) in the setting of inadvertently sampled parathyroid tissue or lesions (PTL) during "thyroid" or "neck" FNA, the authors review their experience at a large, tertiary care academic medical center. All cases of inadvertent sampling of PTL during "thyroid" or "neck" FNA were identified by computer search. The cytologic and histologic material was reviewed and pertinent clinical data including patient demographics, serum calcium, intact serum PTH (PTH-s), and intact PTH-r was recorded. The cytologic interpretations and histologic diagnoses were also recorded. Of 3,521 cases of total thyroid and neck FNA during the study 21 (0.59%) cases of histologically confirmed sampling of PTL were identified. In all 10 cases with PTH-r the level was markedly elevated (range 248-240,075 pg/mL) and in every case PTH-r/PTH-s was elevated (range 3.67-458.3). In all 10 cases with PTH-r the cytologic diagnosis was PTL or included PTL in the differential. In 4111 cases without PTL-r diagnoses of thyroid neoplasm or suspicious for thyroid neoplasm were rendered, each resulting in thyroidectomy. PTH-r has utility in differentiating PTL from thyroid lesions in the setting of inadvertent sampling of PTL during thyroid or neck FNA. Cellular specimens with features not typical for thyroid lesions should be triaged for PTL-r. Routine use of PTH-r will result in appropriate triage of patients to less aggressive excisional biopsies rather than unnecessary thyroidectomy.