Large non-functioning substernal parathyroid cyst: A case report and review of the literature

Mediastinal parathyroid cyst: A case report and review of the literature

Mediastinal parathyroid cysts (MPCs) are extremely rare, benign lesions arising from the parathyroid glands and residing within the thoracic cavity. This study aims to advance understanding of MPC, emphasizing accurate diagnosis and management approaches for this rare condition. A 46-year-old woman presented with dysphagia for one week. Blood tests revealed elevated parathyroid hormone (PTH) (112.8 pg/mL) and normal serum calcium (9.54 mg/dL). Ultrasonography identified a large, well-defined cystic nodule measuring 46 × 30 × 25 mm, extending retro-sternally in the right upper third of the chest. A subsequent high-resolution computed tomography scan of the chest revealed a large space-occupying lesion (47 × 43 × 31 mm) in the superior mediastinum, near the esophagus, suggesting an esophageal duplication cyst or, less likely, a bronchogenic cyst. Video-assisted thoracoscopic surgery (VATS) was performed, and the entire cyst was excised, confirmed histologically as a mediastinal parathyroid cyst. Mediastinal involvement of PCs poses diagnostic challenges due to their rarity and diverse clinical presentations. Surgical excision is necessary for symptomatic cases, with VATS emerging as a favorable approach.

99mTc-methoxyisobutylisonitrile single-photon emission computed tomography/computed tomography parathyroid imaging in the diagnosis of functional parathyroid cysts: an initial experience

Background

Functional parathyroid cysts (FPCs) are rare and difficult to diagnose with noninvasive methods. The aim of this study was to evaluate the diagnostic value of 99mTc-methoxyisobutylisonitrile (99mTc-MIBI) single-photon emission computed tomography/computerized tomography (SPECT/CT) parathyroid imaging in the diagnosis of FPCs and to account for its performance.

Methods

The data from 10 patients with suspected parathyroid cysts (PCs) who underwent 99mTc-MIBI SPECT/CT parathyroid imaging between 2012 and 2022 were retrospectively evaluated. The diagnostic value of 99mTc-MIBI SPECT/CT parathyroid imaging for FPCs was analyzed.

Results

Surgical resection was performed in six cases and parathyroid puncture was performed in four cases. The sensitivity of 99mTc-MIBI SPECT/CT for FPCs was 100.0% (3/3), with a specificity of 100.0% (7/7) and an accuracy of 100.0% (10/10). The postoperative pathological findings in three cases of FPCs were parathyroid adenoma, parathyroid adenoma with hemorrhage, and parathyroid adenoma with cystic degeneration, respectively. The diagnostic accuracy of ultrasound and CT for PCs was only 22.22% (2/9) and 25.0% (1/4), respectively, and neither modality could indicate whether the cysts were functional or not.

Conclusions

99mTc-MIBI parathyroid SPECT/CT imaging has a high value in the diagnosis of FPCs in patients with suspected PCs, and an intense ring-shaped accumulation of radioactivity in the cyst wall on 99mTc-MIBI imaging suggests that the patient may have FPCs.