Endocrine Abstracts

Introduction: The risk of malignancy in thyroid nodules is reported by the Bethesda system by performing fine needle aspiration biopsy (FNAB). Atypia of undetermined significance(AUS) or follicular lesion of undetermined significance(FLUS)(Bethesda 3) and suspicious for a follicular neoplasm (Bethesda 4) create uncertainty about treatment and follow-up. Molecular tests, ultrasonographic features of the nodules, and calcitonin level help us for this uncertainty. Here, we will present a patient whose FNAB cytology was Bethesda 3 and Bethesda 4.

Case: A 53-year-old female patient was admitted to our outpatient clinic after detecting a thyroid in neck ultrasound. She had familial Mediterranean fever, osteoporosis, and renal transplantation (5 years ago). In addition, the patient stated that she had been operated on the parathyroid gland while she was receiving dialysis treatment. There was no document related to parathyroid surgery. In laboratory tests, thyroid function tests, calcitonin, calcium levels were normal. 25-OH vitamin D, parathormone level, creatinine, eGFR were 14 ng/ml, 152 pg/ml, 1.51 mg/dl, 39 ml/minute respectively. Secondary hyperparathyroidism due to vitamin D deficiency was considered. On thyroid ultrasound, a hypoechoic nodule that containing cystic degeneration areas was observed adjacent to inferior carotid artery in the right lobe. The dimensions of nodüle were 9.7x11.4x13.7 mm. FNAB was reported as Bethesda 3. The second FNAB cytology was also reported as Bethesda 4. Molecular testing could not be performed in our hospital. The microscopy of FNAB revealed “some of the cells were small, round, monotonous nuclei with pale cyanophilic cytoplasm with unclear borders”. No uptake suggestive of parathyroid lesion was observed in parathyroid scintigraphy. Third FNAB cytology was nondiagnostic; Parathormone washout was 525 pg/ml. Due to the high suspicion of parathyroid lesion, fourth FNAB and diluted PTH washout were performed. Fourth FNAB cytology was Bethesda 3, diluted parathormone level was 103871 pg/ml. The lesion was evaluated as intrathyroidal lesion (adenoma or parathyroid seeding due to surgery). Follow-up was planned for the patient.

Conclusion: In parathyroid lesions evaluated as thyroid nodules, FNAB cytology and microscopy give us an idea in terms of intrathyroidal parathyroid lesion. Parathyroid scintigraphy also does not always show uptake. In this situation, PTH washout can be done. If the ultrason features, FNAB microscopy and PTH washout are inconsistent, diluted PTH washout may provide accurate results due to possible hook effect. In addition, intrathyroidal parathyroid seeding should also be kept in mind in patients who have undergone parathyroid surgery for tertiary hyperparathyroidism.