Session: SAT 199-223-Disorders of Bone & Calcium Homeostasis: Case Reports
Poster Board SAT-200
We report on a case of unsuspected parathyroid lesion whose two FNA resembled thyroid lesions.
A 31-year-old man presented with a right neck mass. Palpation of the thyroid glands showed a 3-cm nodule in the right lobe and FNA was performed. The cytology was reported as “intrathyroidal lymphoidal hyperplasia”. After observation for 5 years, the size of nodule was enlarged. Repeated FNA was done with result of Hurthle cell lesion. Surgeon decided to perform right lobectomy. His preoperative laboratory investigations revealed normal thyroid function tests, elevated serum calcium of 13.5 mg/dL (reference range, 8.5-10.1 mg/dL), and increased parathyroid hormone (PTH) level of 1,859 pg/mL (reference range, 15-65 pg/mL). Then he was referred to endocrinologists. On ultrasound examination, a 2.8-cm heterogenous hypervascular mass was found inferior to right lobe of thyroid gland. MIBI scan showed increased uptake corresponding to ultrasound findings. Careful systemic history taking revealed that he had been suffered from chronic knee pain for 7 years. Therefore, parathyroid carcinoma was suspected, and then the en bloc resection was performed. The pathology result was parathyroid carcinoma. Immunohistochemical (IHC) staining of tumor cells revealed positive immunoreactivity for PTH but negative for thyroglobulin. In addition, patient had ossifying fibroma at the right mandible since he was 10 years old. The genetic analyses were done in patient’s blood and parathyroid tissue and found somatic frameshift mutation of CDC73 gene in exon1 (c.70delG) caused premature stop codon in amino acid 26 (p.Glu24Lysfs*2). The final diagnosis was parathyroid carcinoma with hyperparathyroidism-jaw tumor syndrome. FNA cytology of parathyroid can mimic thyroid lesion. The oxyphil cells and chief cells present in the parathyroid resembled Hurthle cells and lymphocytes respectively. PTH assay in FNA is also useful in differentiating parathyroid from thyroid tissue.
It is difficult to distinguish parathyroid lesions from thyroid lesions based on solely FNA cytomorphologic diagnosis because of their morphologic similarities.Therefore, it is important to consider and relate the whole information from careful clinical history taking, laboratory, imaging studies, and FNA. PTH assay in FNA specimen and IHC staining can definitely distinguish between parathyroid and thyroid lesions.
Nothing to Disclose: SK, PS, NC, OT, PS, RA, CS
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