Diagnostic pitfalls in a cystic ectopic intrathyroidal parathyroid adenoma mimicking a nodular goiter

Abstract

Rationale: Cystic parathyroid adenomas are rare and seldom arise in ectopically located glands which may be found within the carotid sheath, mediastinum, thymus, or thyroid grand. They cannot be detected consistently by any imaging methods. Unusual symptoms may bring about certain pitfalls and difficulties for the diagnosis of primary hyperparathyroidism (PHPT) caused by cystic parathyroid adenomas. Until now, there are no specific guidelines on the management of cystic ectopic intrathyroidal parathyroid adenoma (ETPA). Patient concerns: An 82-year-old male musician presented abrupt thyroid enlargement, hoarseness, and trachea compression when he was playing the clarinet. Thyroid and renal function tests were normal. Serum-free calcium and parathyroid hormone (PTH) were in high concentration. Thyroid ultrasonography (US) detected a giant and cystic nodule within right thyroid lobe, which is the very image of cystic nodular goiter. Parathyroid US was negative. The cystic nodule had a decreasing radioactive uptake of Technetium-99m-methoxyisobutylisonitrile ( 99m Tc-MIBI). At patient's request, the invasive fine-needle aspiration (FNA) was not conducted. Diagnoses: The patient was initially diagnosed as cystic nodular goiter and inconclusive PHPT. Interventions: Enucleation of solitary cystic intrathyroidal nodule was conducted. Outcomes: The cystic nodule strongly resembled a nodular goiter grossly, but it was proved cystic ETPA by histopathology. Postoperative follow-ups found that serum-free calcium and PTH decreased sharply into normal range, and hoarseness and trachea displacement were obviously improved. Lessons: The diagnosis of cystic ETPA is easily overlooked for its rarity. Diagnostic pitfalls, including atypical symptoms, inconclusive imaging manifestation, and unidentified gross specimen, are highlighted. They make the diagnosis of PHPT caused by cystic ETPA challenging. Patients would rather choose surgical excision directly than invasive FNA. Acute hemorrhage of the preexisting ETPA may account for the cystic degeneration.

Intrathyroidal parathyroid adenoma mimicking thyroid cancer

“…Even so, they are difficult to be distinguished from thyroid nodules, which may exhibit similar morphology [3,9]. On functional imaging with 99m Tc sestamibi scan, both thyroid nodules and PAs may be visualized and therefore, the presence of tracer accumulation is not always indicative of a PA. Cystic PAs however are further complicated by the lack of tracer accumulation as seen in our case and other reports [7,10].…”

“…According to a previous large series, intrathyroidal PAs account for 1% of all PAs [5]. Cystic intrathyroidal PAs are even rarer, with a few cases described in the literature so far [6][7][8]. The rarity of this entity makes the pre-operative diagnosis elusive.…”

Primary Hyperparathyroidism Secondary to a Sestamibi-Negative Cystic Parathyroid Adenoma

“…PHPT secondary to functional cystic parathyroid adenomas can pose challenges to clinicians, not only because they are rare, but also as negative sestamibi scans may erroneously increase suspicion for a thyroid etiology of functional parathyroid cysts. One case of a cystic parathyroid adenoma was initially diagnosed as a cystic nodular goiter and inconclusive PHPT as the patient declined FNA [ 6 ]. There are multiple treatment options for cystic parathyroid adenomas.…”

Simultaneous intrathyroidal parathyroid adenomas and multifocal papillary thyroid carcinoma in a patient with kidney transplantation: a case report

“…Focal uptake in the right superior thyroid nodule on SPECT/CT is consistent with IPA due to persistent hyperparathyroidism after kidney transplantation. Some studies report that the combination of ultrasonography and 99m TcO 4 -sestamibi SPECT can accurately locate IPA [8–10, 23–27].…”

“…Ultrasonography can help localize parathyroid disease and assess concomitant thyroid disease. However, ultrasonography has difficulty diagnosing intrathyroidal parathyroid adenoma (IPA) and particularly struggles in the differential diagnosis of thyroid nodules, IPA and papillary thyroid carcinoma [8]. 99m TcO 4 -sestamibi single-photon emission computed tomography/computed tomography (SPECT/CT) has a high sensitivity (84%) and positive predictive value (95%) and especially improves upon the detection rate of ultrasonography for ectopic tissue, which is likely to be missed by ultrasonography [9].…”