Ultrasonically guided localization, tissue verification, and percutaneous treatment of parathyroid tumours

Abstract

The conventional treatment of patients with P-HPT is neck-surgery. A variety of imaging techniques has been used for localization of PT. These techniques are most conveniently divided into two categories: noninvasive imaging methods (US, CT, MR, thallium-technetium subtraction scintigraphy) and invasive localization procedures (imaging-guided biopsy/aspiration, parathyroid angiography, parathyroid venous sampling). Employing US it seems possible to localize about 2/3 of PT in patients with P-HPT before initial surgery. Most often, the PT appears as a rounded homogeneous mass with a lower echogenicity than that of the normal thyroid gland. However, the US characteristics may vary. False negative US findings are due to difficulties in detecting very small PT, and the inability to visualize PT localized in areas inaccessible to US. In patients with multinodular goitres the PT might be overlooked. False positive findings are mainly caused by misinterpretation of thyroid nodules as being enlarged parathyroid glands. In order to secure a reliable tissue diagnosis, US guided fine needle biopsies can be performed. Three different techniques were tested and found usable: aspiration biopsy either for PTH-measurement or cytological examination, and tissue biopsy for histological examination. When using aspiration biopsy for PTH-measurements, aspirates from both the suspected parathyroid tissue and from corresponding thyroid tissue are immunochemically analyzed for PTH concentration. A positive PTH-gradient-that is a higher PTH-concentration in the aspirates from the suspected PT-strongly indicates the presence of a PT. The usefulness of this technique may be hampered by accessibility and cost of the PTH-analysis. Cytological discrimination between parathyroid and thyroid cells might be difficult especially in specimens of low cellularity. Cytological examination of parathyroid cells is a method recently introduced in parallel with the possibilities of parathyroid visualization and percutaneous aspiration. Therefore, at present, reliable recognition of parathyroid cells can be expected only from cytologist with special interest and experience in parathyroid cytology. The histological appearance of parathyroid tissue is well known to most pathologists. The histological diagnosis of tissue samples obtained by US guided tissue biopsies is reliable. However, sufficient tissue for examination is obtained only in about half of the cases.(ABSTRACT TRUNCATED AT 400 WORDS)