Abstract
A 46-year-old woman presented at Iwaki Kyoritsu General hospital with an approximately 3.0×2.0cm elastic, hard, movable right neck mass.
On admission, the serum intact parathyroid hormone (intact PTH) level measured by radioimmunoassay was 1, 092 pg/ml: about 15 times the upper limit of the normal range. Fine needle aspiration cytology was performed on the mass. The aspirated material showed cohesive clusters with papillary formation, intra-nuclear inclusion and nuclear groove, which were suggestive of thyroid papillary carcinoma. We made a preoperative diagnosis of suspected co-existent parathyroid adenoma and thyroid papillary carcinoma. Tumor resection and intraoperative rapid diagnosis were planned. At operation, a well-encapsulated and smooth surfaced tumor, measuring about 1.5×2.5×0.5cm, located on the right dorsal side of the upper lobe of the thyroid, was resected. Stamp cytology specimens showed small clusters of uniform sized cells with a small follicular arrangement, possessing round or oval nuclei and abundant granular cytoplasm. Frozen sections showed various sized follicles composed of ovoid cells, with eosinophilic cytoplasm, and absence of fat cells within the proliferation. These cellular and histological appearances were characteristic of parathyroid adenoma. She underwent additional right thyroidectomy. Histological examination of the resected thyroid revealed three small nodular lesions of thyroid papillary carcinoma in the upper lobe each measuring about 5mm in diameter.
Since parathyroid adenomas display diverse histologic appearances, fine-needle aspiration may rarely lead to a mistaken diagnosis of thyroid neoplasm in patients with parathyroid adenomas. On the other hand, between 5% and 12% of patients with parathyroid adenomas harbor a coexistent non-medullary thyroid carcinoma. This co-existence may also result in a discrepancy between the clinical impression and the aspiration cytology diagnosis.
This case merits reporting in that the diagnostic pitfalls in fine-needle aspiration cytology of parathyroid adenomas must be considered.
