99mTc-MIBI single photon emission computed tomography/computed tomography for the incidental detection of rare parathyroid carcinoma

Abstract

This study aimed to evaluate the characteristics of parathyroid carcinoma and to validate the diagnostic value of 99mTc-methoxyisobutylisonitrile (MIBI) single photon emission computed tomography/x-ray computed tomography (SPECT/CT) for differentiating between parathyroid carcinoma and hyperparathyroidism. Four consecutive patients with suspected primary hyperparathyroidism were enrolled in this study and underwent 99mTc-MIBI SPECT/CT, ultrasonography, enhanced CT, and MRI. Serum parathyroid hormone (PTH) and calcium were measured. All primary and recurrent lesions showed high focal uptake on 99mTc-MIBI image, whereas metastatic lymph nodes gave false negative results. The serum PTH was 165.14 ± 90.26 pmol/L, which declined rapidly after surgery. One patient with a persistently high PTH (147.5 pmol/L) after surgery presented with multiple lymphadenopathy in the neck. Higher expression of chromogranin A (CgA) further confirmed parathyroid carcinoma as a rare endocrine tumor. Parathyroid carcinoma is thus usually diagnosed incidentally based on nonspecific multiorgan symptoms of hypercalcemia and hyperparathyroidism. 99mTc-MIBI SPECT/CT may help to localize the parathyroid carcinoma, while MRI is valuable for detecting metastasis. Serum PTH and CgA serve as circulating biomarkers in parathyroid carcinoma, and raised levels of PTH and CgA together with locoregional lymphadenopathy may indicate parathyroid carcinoma. Further studies are needed.

Case series of diagnosis and surgery challenges in parathyroid carcinoma

“…Our study utilized neck US as part of the routine examination. Two of six PC cases were identified by neck US, while two patients who underwent MIBI scan yielded findings suggestive of PA. Localization may be aided by MIBI scan, but no sole imaging modality has been fully validated for the detection of PC [4] . Imaging must be performed in conjunction with biochemical profiles and histopathologic findings.…”

“…Recurrences usually occur within 2 to 3 years after the initial surgery, mostly within the regional operative field, and are reflected by marked hypercalcemia and hyperparathyroidism identified at follow-up [4] . Surgery is rarely curative in cases with distant metastases, although palliative debulking of the tumor mass may aid in controlling hypercalcemia [11] .…”

“…90 % of MEN1 patients found presented with hyperparathyroidism [2] . Primary hyperparathyroidism is usually characterized by hypercalcemia, which occurs due to excessive autonomous secretion of parathyroid hormone (PTH) and is three to four times more likely to be found in women aged 50 to 65 years [3] , [4] .…”

Mediastinal Parathyroid Cancer

“…A larger size of parathyroid lesions favors their detection by sestamibi scans (MIBI) [ 72 ], whilst PTH and calcium excess do not [ 73 ] and lymph nodes often remain unapparent on such scans [ 29 ]. A detailed examination in limited-size PC cohorts show that a combination of US with CT and MIBI or CT with MIBI achieves a higher accuracy in localization of PC [ 30 ], but do such tests not convincingly aid in the diagnosis of malignancy unless expert and, as yet, unconfirmed criteria are applied [ 31 ].…”

“…Potential malignancy is indicated by a syndromic context such as Hyperparathyroidism-Jaw Tumour Syndrome (HP-JTS) with CDC73 mutations [ 26 , 27 ]. Cross-sectional imaging [ 28 ] and MIBI SPECT-CT [ 29 , 30 , 31 ] have limited differentiating power. The contribution of FDG-PET CT is insufficiently explored [ 32 ], but F-18 fluorocholine PET/CT holds promise [ 33 , 34 , 35 ] and may detect lesions evading FDG-PET detection [ 33 ].…”