Large non‐functioning parathyroid cysts: our institutional experience of a rare entity and a possible pitfall in thyroid cytology

Abstract

Large non-functioning parathyroid cysts: our institutional experience of a rare entity and a possible pitfall in thyroid cytology Objective: Large non-functioning parathyroid cysts represent a rare entity with a benign clinical course. They may be misdiagnosed as thyroid cystic neoplasms on fine needle aspiration cytology (FNAC), resulting in inappropriate surgical treatment. We evaluated our institutional experience in the diagnosis of large parathyroid cystic lesions underlining all the differential diagnoses and pitfalls. Methods: In the period between 1998 and 2012, we reported the cytology of eight large (>2.5 cm) parathyroid cystic lesions (all female patients) with histological control. The aspirations were performed with a 25-gauge needle with ultrasonographic guidance. The aspirated material was processed with liquid-based cytology (LBC). All the patients had normal serum parathyroid hormone (PTH) and calcium. Results: The cytological samples showed a fluid watery component without colloid and few or absent epithelial cells. The resulting negativity for thyroglobulin and positivity for PTH, carried out on the cystic fluids, suggested parathyroid lesions rather than either thyroid cystic lesions (including follicular thyroid neoplasm) or cystic malignant lesions. All the patients underwent surgery without complications. Conclusions: To the best of our knowledge, this is one of the largest series with cytohistological evaluation of large parathyroid cysts. The incidence of large parathyroid cysts remains controversial as most patients are asymptomatic. FNAC may be performed with conclusive results in the majority of cystic cases. The detection of PTH and calcium on the cystic liquid is likely to achieve a correct cytological diagnosis, allowing adequate treatment and ruling out a more frequent thyroid lesion.

Pitfalls in the cytological assessment of thyroid nodules

“…Ciliated cells, lymphocytes, squames, colloid, keratin are the components helping in the differential diagnosis (5,6). Colorless or water-clear fluid mostly suggest parathyroid cysts, the others as well as thyroid cysts/ pseudocysts are characterized by yellowish to brown cyst contents (5,8). The biochemical analysis of the cyst fluid has great value in differentiating parathyroid cysts from the others (5,8).…”

“…Colorless or water-clear fluid mostly suggest parathyroid cysts, the others as well as thyroid cysts/ pseudocysts are characterized by yellowish to brown cyst contents (5,8). The biochemical analysis of the cyst fluid has great value in differentiating parathyroid cysts from the others (5,8). PTC associated with thyroglossal duct cyst is very rare but may cause a real challenge.…”

Parathyroid cyst- missed diagnosis or a misdiagnosis: A case report

“…One theory proposes that these cysts result from a vestigeal remnant of the third or fourth branchial cleft or from the persistent Kursteiner canals. 13 Other theory proposes that it results from the infarction and degeneration of a parathyroid adenoma or due to coalescence of multiple small cysts present in the parathyroid gland. 12 A thorough head and neck examination along with a FNAC and USG can be helpful in arriving at a diagnosis.…”

Cytomorphologic features distinguishing Bethesda category IV thyroid lesions from parathyroid

“…[45181920] Serum PTH level or hypercalcemia can be used for suspicion of hyperparathyroidism; however, it is not useful in cases of nonfunctioning parathyroid lesions. [21] More recent studies have described the varying appearance of parathyroid on cytology and the common diagnostic pitfalls. [12131416] While cytological features of parathyroid tissue FNA have been reported, the criteria specifically distinguishing parathyroid tissue from Beth-IV thyroid lesions have not been previously reported to the best of our knowledge.…”