ULTRASOUND-GUIDED FINE-NEEDLE ASPIRATION OF PARATHYROID LESIONS - A MORPHOLOGICAL AND IMMUNOCYTOCHEMICAL APPROACH

Ultrasound-guided (US) fine-needle aspiration (Fn;A) can successfully localize abnormal parathyroid tissue (PT) preoperatively in hyperparat hyroid patients. Samples from 12 patients with primary hyperparathyroi dism evaluated using this technique since 1990 at the National Institu tes of Health form the basis of this report. Eleven patients had under gone previous parathyroid surgery that failed to correct their hyperpa rathyroidism. Cytological evaluation and C-terminal (midmolecule) para thyroid hormone radioimmunoassay (PTH RIA) were performed on all sampl es. When sufficient material was available, immunocytochemical stains for chromogranin and thyroglobulin were performed. All cytological dia gnoses were made without knowledge of the PTH RIA results. Using a com bined approach of cytology and immunocytochemistry, six of 12 of the s amples (50%) were diagnosed as PT. Follow-up on these six patients was confirmatory. Four of 12 samples (33%) were identified as thyroid; on e of these patients had a PT adenoma identified in another location (t he remaining three patients await further localization studies). Two o f 12 samples (17%) could not be diagnosed because of insufficient cell ularity; in both patients PT lesions were found in other locations. Mo rphological features of PT in FNA include the presence of cellular tis sue fragments with epithelial cells arranged perivascularly around cap illary cores, an overall organoid or trabecular architecture, and freq uent microacini. Parathyroid tissue cells have round, fairly uniform n uclei measuring 6 to 8 mu m. Clusters of larger oxyphil cells may show considerable anisonucleosis. The absence of features of thyroid tissu e such as hemosiderin-laden macrophages, abundant colloid, and paravac uolar granules is significant. However, in cases of intrathyroidal PT, admired thyroid material included in the aspiration tract may be pres ent. Immunocytochemical stains for chromogranin, which is present in p arathyroid tissue but not thyroid follicular cells, were positive in s ix of six samples interpreted as PT by cytology. No thyroglobulin stai ning was observed in any of the four of six PT samples for which mater ial was available. C-terminal (midmolecule) PTH RIA correlated with cy tological diagnoses in 100% of samples. Parathyroid hormone levels ran ged from 1,300 to 262,000 pg/mL (normal blood level, 50 to 340 pg/mL) in the six samples diagnosed as PT by cytology. Parathyroid hormone RI A levels in the six non-PT samples were below normal blood values. The combined approach of cytology and immunocytochemistry provides high d iagnostic accuracy in the interpretation of US-guided FNA for preopera tive localization of parathyroid tissue. Copyright (C) 1995 by W.B. Sa unders Company