|Year : 2021 | Volume
| Issue : 2 | Page : 118-121
A case of predominantly chief cell parathyroid adenoma showing early washout of 99mTc MIBI detected by single-photon emission computerized tomography-computed tomography (SPECT-CT)
KB Sricharan1, Rayudu Amrutha Lakshmi1, VS Krishna Mohan1, Gali Sai Chandana2, Ranadheer Manthri Gupta1, Mutheeswaraiah Yootla3, Tekchand Kalawat1
1 Department of Nuclear Medicine, Sri Venkateswara Institute of Medical Sciences, Tirupati, Andhra Pradesh, India
2 Department of Pathology, Sri Venkateswara Institute of Medical Sciences, Tirupati, Andhra Pradesh, India
3 Department of Surgery, Sri Venkateswara Institute of Medical Sciences, Tirupati, Andhra Pradesh, India
|Date of Submission||30-Oct-2019|
|Date of Decision||22-Feb-2020|
|Date of Acceptance||18-Jul-2020|
|Date of Web Publication||17-Jul-2021|
Professor and HOD, Department of Nuclear Medicine, Sri Venkateswara Institute of Medical Sciences, Tirupati 517 501, Andhra Pradesh
Source of Support: None, Conflict of Interest: None
Parathyroid adenoma is a major clinical manifestation of primary hyperparathyroidism, which is usually diagnosed with invasive methods. In most of the cases delayed washout of radio tracer is appreciated on routine parathyroid scintigraphy. Exceptionally in some cases, early washout of tracer is seen which results in false negative parathyroid scintigraphy due to various factors such as expression of p glycoprotein, expression of multidrug resistant protein 1, small glands and presence of chief cells. We present a the case of a patient with parathyroid adenoma showed fast tracer clearance on delayed images but anatomically localized by the additional images using single-photon emission computed tomography-computed tomography (SPECT-CT). The anatomically localized structure further characterized by histopathological examination with presence of abundant chief cells, the cause of poor tracer retention and fast clearance in delayed images. Knowledge about differential presence of chief cells and oxyphilic cells in various parathyroid adenomas must be considered by nuclear physician to avoid false negative parathyroid adenoma.
Keywords: 99mTechnetium methoxyisobutylisonitrile (99mTc MIBI) parathyroid scintigraphy, early washout parathyroid adenoma, parathyroid chief cells, single-photon emission computerized tomography-computed tomography
|How to cite this article:|
Sricharan K B, Lakshmi RA, Krishna Mohan V S, Chandana GS, Gupta RM, Yootla M, Kalawat T. A case of predominantly chief cell parathyroid adenoma showing early washout of 99mTc MIBI detected by single-photon emission computerized tomography-computed tomography (SPECT-CT). J Clin Sci Res 2021;10:118-21
|How to cite this URL:|
Sricharan K B, Lakshmi RA, Krishna Mohan V S, Chandana GS, Gupta RM, Yootla M, Kalawat T. A case of predominantly chief cell parathyroid adenoma showing early washout of 99mTc MIBI detected by single-photon emission computerized tomography-computed tomography (SPECT-CT). J Clin Sci Res [serial online] 2021 [cited 2021 Aug 3];10:118-21. Available from: https://www.jcsr.co.in/text.asp?2021/10/2/118/321693
| IntroductioN|| |
Primary hyperparathyroidism (PHPT) is a disorder characterised by autonomous production of parathyroid hormone (PTH), which is classically characterised as high abnormal PTH in association with high or even normal calcium. The incidence of PHPT is approximately 28 cases per 100,000 individuals in the general population. The incidence is highest between 50 and 60 years of age, affecting 2–3 times more commonly in females. The vast majority of cases (90%–95%) are sporadic.
Patients with PHPT usually present with non-specific symptoms such as fatigue, pain and weakness as well as polydipsia, polyuria, nephrolithiasis, constipation, anorexia, nausea and vomiting. Evaluation consists of radiographic studies and subsequent surgical exploration. In non-invasive methods, 99mTc MIBI SPECT-CT is one of the imaging modalities available for accurate localisation of parathyroid adenomas with anatomical landmarks, which has been used in minimising the invasiveness of surgery of both non-ectopic and ectopic adenomas. Here, we report a case of early washout parathyroid adenoma on SPECT-CT.
| Case Report|| |
A 44-year-old male presented with pain abdomen with a history of recurrent renal calculi. The patient had no fever, vomiting, dysuria and clinically palpable neck swellings. The patient underwent routine serological investigations which showed serum calcium level of 12.7 mg/dL (normal range: 8.00–10.50 mg/dL), phosphorous level of 2.1 mg/dL (normal range: 2.50–4.80 mg/dL) and 25 Vitamin D level of 40.5 ng/mL (normal range: 30.00–100.00 ng/mL). In view of the raised serum calcium and decreased serum phosphorous levels, measurement of serum PTH levels was advised, and the value came to be 307.3 pg/mL (normal range: 12.00–88.00 pg/mL). Ultrasound neck showed hypoechoic hypervascular lesion measuring 1.3 cm × 1.4 cm, inferior to the lower pole of the right lobe of the thyroid gland.
Further, the patient was referred to the department of nuclear medicine to confirm parathyroid adenoma in view of increased serum PTH and calcium levels and decreased phosphorous levels. The patient underwent dual-phase parathyroid scintigraphy using 99mTc MIBI. Planar images of the neck and chest in the anterior, right anterior oblique, left anterior oblique, right posterior oblique and left posterior oblique were acquired in a 256 × 256 matrix at 15 Min (early) and 90 Min (delayed), as shown in [Figure 1], following the iv injection of 800 MBq 99mTc MIBI using a dual-head gamma camera. The initial images acquired at 15 Min showed diffuse increased tracer uptake in the thyroid gland along with an intense focal area of tracer concentration at the right inferior pole of thyroid. During delayed image acquired at 90 Min, there was no radiotracer localisation in the focal uptake site as seen in early images. The lesion was suspected to be a parathyroid adenoma based on the high uptake in the early scan, albeit one which did not retain the radiotracer long enough.
|Figure 1: 99mTc MIBI dual-phase, parathyroid scintigraphy images initial 15 Min (upper row) anterior (a), left anterior oblique (b) and right anterior oblique (c) showing increased tracer uptake in thyroid parenchyma with a small focal uptake site (right inferior parathyroid adenoma) just below the thyroid right lobe lower pole. Delayed, 90 Min images (lower row), anterior (d); left anterior oblique (e) and right anterior oblique (f) showing, instead of retention of radiotracer in parathyroid adenoma, washout along with thyroid parenchyma Arrow points to the right lower pole of thyroid gland|
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The SPECT-CT imaging [Figure 2] of the same part revealed a hypodense lesion in the CT component at the same place where there was an increased uptake, thereby strongly providing evidence to corroborate the suspicion of adenoma. Later, the patient underwent right inferior parathyroidectomy. Intraoperative PTHs levels decreased from 307.3 pg/mL (pre-operative state) to 32.5 pg/mL (after 20 Min, postoperatively). Histopathological examination (HPE) of the specimen [Figure 3] was consistent with predominantly chief cells, confirming parathyroid adenoma.
|Figure 2: Computed tomography scan, coronal (a), sagittal (b), single-photon emission computed tomography/computed tomography coronal (c) and sagittal (d) showing well-defined margins and globular shape of right inferior parathyroid adenoma, measuring 2.0 cm × 1.4 cm × 1.0 cm (white arrow) corresponding to early tracer washout|
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|Figure 3: Microphotograph of the parathyroid gland showing a capsulated lesion composed of large polygonal cells (chief cells) with clear cytoplasm and a centrally placed nucleus. Adjacent rim of normal parathyroid tissue seen (Haematoxylin and eosin, 200). Inset shows chief cells with clear cell morphology (Haematoxylin and eosin, 400)|
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| Discussion|| |
Parathyroid adenoma is a part of a spectrum of parathyroid proliferative disorder that includes parathyroid hyperplasia, parathyroid adenoma and parathyroid carcinoma. Patients with PHPT typically present with elevated serum calcium levels and elevated serum PTH levels. Nearly 80%–85% of PHPT is caused by parathyroid adenoma, followed by primary parathyroid hyperplasia (15%) and parathyroid carcinoma (5%). Both invasive and non-invasive investigations are used in the evaluation of parathyroid adenoma. Non-invasive methods are neck ultrasonography, planar 99mTc MIBI dual-phase scintigraphy, 99mTc MIBI SPECT-CT, magnetic resonance imaging and positron emission tomography-CT.
99mTc MIBI dual-phase scintigraphy with or without additional images of SPECT-CT imaging is now a widely used technique for the detection and localisation of both ectopic and non-ectopic parathyroid adenomas., 99mTc MIBI molecules after iv injection can cross the cell membranes by passive diffusion, and get concentrated in the region of the mitochondria because of its lipophilic nature. Presence of mitochondrial-rich oxyphilic cells will show intense tracer concentration in parathyroid adenoma.
Various factors are reported, which results in false-negative parathyroid adenoma findings. The most common factors are size of the parathyroid gland, where detection of smaller glands is less likely than the larger glands. Other factors such as presence of abundant chief cell content, P-glycoprotein expression and multidrug resistance protein 1 expression will cause early washout of tracer from tumour cells., A positive scan associated with the presence of higher number of mitochondria-rich oxyphilic cells and negative scan associated with higher number of clear cells using subtraction technetium–thallium scanning. In our case, post-operative HPE showed has been reported predominantly chief cells with clear cytoplasm and a centrally placed nucleus. Abundant number of chief cells with relatively less mitochondria may be the reason for the early washout of tracer, as seen in this case. This case highlights the fallacies of 99mTc MIBI dual-phase scintigraphy in the detection of parathyroid adenoma. Clinical and radio-nuclear scan correlation with a high index of suspicion or alertness is important to not to miss these types of cases.
99mTc MIBI SPECT-CT is one of the most sensitive and specific investigations for localisation of parathyroid adenoma. Primary parathyroid adenoma with predominant oxyphilic cells on histology will show delayed washout of tracer, thereby detected on dual-phase parathyroid scan. However, in certain cases where chief cells are abundant with P-glycoprotein expression, planar imaging will show early washout of tracer, which results in false-negative scan. In these cases, SPECT-CT is more sensitive and specific in the diagnosis of early washout parathyroid adenoma, as seen in our case.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3]