Use of pre-operative Tc99m-Sestamibi scintigraphy and intraoperative parathyroid hormone monitoring to eliminate neck exploration in mediastinal parathyroid adenocarcinoma

Mediastinal parathyroid carcinoma: a case report and review of the literature

BACKGROUND

Parathyroid carcinoma (PC) is an uncommon cause of primary hyperparathyroidism (PHPT) and particularly rare in the mediastinum. Herein, we present a case of mediastinal PC and conduct a related literature review.

CASE PRESENTATION

We described a case of a 50-year-old female patient with PHPT due to mediastinal PC. She was initially admitted to a local hospital in her hometown with hypercalcemia and high blood concentrations of PTH (parathyroid hormone). The patient underwent neck parathyroidectomy and pathological examination suggested parathyroid adenoma. Although the overproduction of serum calcium and PTH declined after the surgery, calcium and PTH increased again one month later, so the patient was transferred to our hospital. A 99^mTc-sestamibi scan revealed an ectopic finding in the mediastinum, which was also indicated on the CT image. After removing the mediastinal mass, the metabolism of calcium and PTH quickly reverted to normal and the pathologic features of the mass were consistent with PC. By reviewing the related literature, we noticed that only scattered reports were published before 1982, and those were not included in the present review due to their differences with current radiological examination and treatment methods. After excluding outdated studies, we summarized and analyzed 20 reports of isolated mediastinal PC and concluded that. Parathyroidectomy remains the only curative treatment for the disease. Furthermore, the success of treatment directly depends on accurate preoperative localization.

CONCLUSION

With this study, we emphasize the importance of accurate preoperative diagnosis of mediastinal PC and improve clinicians' understanding of the disease.

Mediastinal Parathyroid Cancer

Parathyroid cancer (PC) is rare, but its pre-operative recognition is important to choose appropriate access strategies and achieve oncological clearance. This study characterizes features of mediastinal parathyroid cancer (MPC) and explores criteria aiding in the pre-operative recognition of malignancy. We assembled data from 502 patients with mediastinal parathyroid neoplasms (MPNs) from a systematic review of the literature 1968−2020 (n = 467) and our own patient cohort (n = 35). Thirty-two of the 502 MPNs (6.4%) exhibited malignancy. Only 23% of MPC patients underwent oncological surgery. Local persistence and early recurrence at a median delay of 24 months were frequent (45.8%), and associated with a 21.7-fold (95%CI 1.3−351.4; p = 0.03) higher risk of death due to disease. MPCs (n = 30) were significantly larger than cervical PC (n = 330), at 54 ± 36 mm vs. 35 ± 18 mm (χ2 = 20; p < 0.0001), and larger than mediastinal parathyroid adenomas (MPA; n = 226) at 22 ± 15 mm (χ2 = 33; p < 0.01). MPC occurred more commonly in males (60%; p < 0.01), with higher calcium (p < 0.01) and parathyroid hormone (PTH) levels (p < 0.01) than MPA. Mediastinal lesions larger than 3.0 cm and associated with a corrected calcium ≥ 3.0 mM are associated with a more than 100-fold higher odds ratio of being malignant (OR 109.2; 95%CI 1.1−346; p < 0.05). The composite 3 + 3 criterion recognized 74% of all MPC with an accuracy of 83%. Inversely, no MPN presenting with a calcium < 3.0 mM and size < 3.0 cm was malignant. When faced with pHPT in mediastinal location, consideration of the 3 + 3 rule may trigger an oncological team approach based on simple, available criteria.

Intraoperative use of optical coherence tomography to differentiate normal and diseased thyroid and parathyroid tissues from lymph node and fat

The purpose of this study is twofold: (1) to determine the feasibility of optical coherence tomography (OCT) to differentiate normal and diseased tissue of the neck region intraoperatively and (2) to evaluate how accurately a cohort of test subjects can identify various tissue types when shown a sample set of OCT images. In this in vivo, prospective, single institutional study, an OCT imaging system (Niris, Imalux, Cleveland, OH) was used to image parathyroid, thyroid, lymph node, and fat tissue in 76 patients during neck surgery. Biopsies were performed for comparison of OCT images with histology in select cases (n = 20). Finally, a group of either surgeons or scientists familiar with OCT (n = 17) were shown a sample of OCT images and asked to identify the tissue. A total of 437 OCT images were analyzed, and characteristic features of each tissue type were identified. OCT demonstrated distinct differences in structural architecture and signal intensity that allows differentiation between thyroid and parathyroid tissues, lymph nodes, and fat. OCT images were also compared with histology with good correlation. There was no difference in correctly identifying OCT-imaged tissue type between surgeons and scientists. This study is the first in vivo OCT imaging study to evaluate both normal and diseased tissues that may be encountered during neck surgery. OCT has the potential to become a valuable intraoperative tool to differentiate diseased and normal thyroid tissue intraoperatively to obtain an "optical biopsy" in real time without fixation, staining, or tissue resection.

An unusual mediastinal parathyroid carcinoma coproducing PTH and PTHrP: A case report

Parathyroid carcinoma (PTCA) is a rare disease, and ectopic PTCA is particularly rare. Parathyroid hormone-related protein (PTHrP) expression in PTCA has not been previously described in the relevant literature to the best of our knowledge. The present study reports a unique case with a mediastinal parathyroid carcinoma producing parathyroid hormone (PTH) and PTHrP. A 53-year-old man presented with hyperparathyroidism symptoms, including fatigue, chest pain, dizziness, muscular soreness, polyuria, night sweats and renal stones. However, neck ultrasound revealed no significantly abnormal thyroid or parathyroid nodules. Tc99m methoxyisobutylisonitrile (Tc99m-MIBI) scintigraphy scanning indicated an ectopic mediastinal parathyroid adenoma. Histopathological examination revealed PTCA, and the tumor tissue was coproducing PTH and PTHrP. The patient underwent successful surgical operation. Serum calcium and PTH levels remained within normal ranges, and there was no tumor recurrence observed at a 3-year follow-up appointment. Although rare, ectopic parathyroid glands may lead to malignant disease. Clinical symptoms, biochemical tests, ultrasound and Tc99m-MIBI scintigraphy scanning may assist with the diagnosis of this disease. Hypersecretion of PTHrP and PTH contributed collaboratively to the pathogenesis of hypercalcemia due to PTCA. Complete surgical resection with microscopically negative margins is the recommended treatment for PTCA and offers the best chance of a cure.

Mediastinal parathyroid carcinoma presenting with severe skeletal manifestations

Parathyroid carcinoma is a rare malignancy, accounting for about 1% of primary hyperparathyroidism. We report the case of a 23-year-old man who presented with poorly united mid-shaft fracture of the left femur with severe hypercalcaemia in the setting of 99 mTc sestamibi-avid lesions in the mediastinal and thoracic vertebrae. The patient underwent surgery, and histopathology revealed a low-grade parathyroid carcinoma. After surgery, the patient developed severe hungry bone syndrome requiring intensive calcium, magnesium and active vitamin D supplementation. A review of the literature was undertaken with regards to mediastinal parathyroid carcinoma, management of refractory hypercalcaemia in this setting and hungry bone syndrome.