Thyroid Research and Practice

CASE REPORT
Year
: 2020  |  Volume : 17  |  Issue : 2  |  Page : 86--88

Intrathyroidal parathyroid adenoma: A perplexing entity


Mohit Gupta1, Deepak Khandelwal2, Vivek Aggarwal3, Nishikant Avinash Damle4, Monika Garg5,  
1 Department of Colorectal Surgery, Bedford NHS Trust, Bedford, UK
2 Department of Endocrinology and Diabetes, Maharaja Agrasen Hospital, New Delhi, India
3 Department of Endocrine Surgery, Maharaja Agrasen Hospital, New Delhi, India
4 Department of Nuclear Medicine, All India Institute of Medical Sciences (AIIMS), New Delhi, India
5 Department of Radiology, Maharaja Agrasen Hospital, New Delhi, India

Correspondence Address:
Dr. Deepak Khandelwal
Department of Endocrinology and Diabetes, Maharaja Agrasen Hospital, Punjabi Bagh, New Delhi
India

Abstract

Intrathyroidal parathyroid adenoma (IPA) can be a cause of failed cervical exploration for primary hyperparathyroidism (PHPT). There is a lot of controversy regarding the correct approach and extent of exploration in such cases. Herein, we report the case of a 37-year-old female who was managed for PHPT with right-sided IPA after correlating preoperative ultrasonography and99mTc-sestamibi scan. A high index of suspicion, preoperative identification, and planning is very important to avoid unnecessary dissection and failure to remove the diseased gland in such cases.



How to cite this article:
Gupta M, Khandelwal D, Aggarwal V, Damle NA, Garg M. Intrathyroidal parathyroid adenoma: A perplexing entity.Thyroid Res Pract 2020;17:86-88


How to cite this URL:
Gupta M, Khandelwal D, Aggarwal V, Damle NA, Garg M. Intrathyroidal parathyroid adenoma: A perplexing entity. Thyroid Res Pract [serial online] 2020 [cited 2020 Dec 2 ];17:86-88
Available from: https://www.thetrp.net/text.asp?2020/17/2/86/289996


Full Text



 Introduction



Although uncommon, an intrathyroidal parathyroid adenoma (IPA) can be an important cause of surgical failure in patients with primary hyperparathyroidism (PHPT).[1] First described by Lahey in the year 1926, an intrathyroidal parathyroid gland (true intrathyroidal parathyroid gland) is a normal or abnormal parathyroid gland, situated totally within the thyroid, surrounded on all aspects by thyroid parenchyma and with no capsule.[2] This entity must be clearly distinguished from the subcapsular/intracapsular parathyroid gland and those glands located in crevices in the thyroid. There is a lot of controversy regarding the correct approach and extent of exploration in cases where an IPA is suspected. The extent ranges from carrying out a bilateral neck exploration along with thymus exploration, to undertaking a partial or complete thyroid lobectomy and even thyroidectomy and enucleation.[3],[4],[5] Herein, we report a case of PHPT resulting from IPA managed at our center.

 Case Report



A 37-year-old woman presented for the evaluation of recurrent renal stones for the last 5 years. On investigations, she was detected to have hypercalcemia (multiple reports ranging between 12 and 14 mg/dl; normal range 8.8–10.8 mg/dl). She denied any bony symptoms, dyspepsia, or proximal muscle weakness. There was no palpable abnormal mass/nodule in the region of the neck. Her intact parathyroid hormone (iPTH) level was 245 pg/ml (normal 15–65 pg/ml), and 25(OH) vitamin D was 31 ng/ml (normal range 30–100 ng/ml). Her thyroid function test was within normal limits. A presumptive biochemical diagnosis of PHPT was made, and she underwent ultrasonography (USG) of the neck for localization of parathyroid adenoma, which revealed a solid hypoechoic lesion of 1.5 cm × 1.5 cm located within the right lobe of the thyroid inferiorly [Figure 1]. No other enlarged/abnormal parathyroid glands could be seen.99m Tc-sestamibi scan was done which revealed an abnormal enhanced uptake in the region of the inferior part of the right lobe of the thyroid [Figure 2]. After correlating the USG report along with the abnormal uptake in the sestamibi scan, a diagnosis of intrathyroid parathyroid adenoma was considered. After detailed discussion and consent with the patient and family, decision was taken for exploration with a possibility of right thyroid lobectomy.{Figure 1}{Figure 2}

The right lower parathyroid gland could not be found anywhere even after detailed exploration including exploration of the thyrothymic ligament. The right lobe of the thyroid was removed based on preoperative imaging after safeguarding the right superior parathyroid gland which appeared normal on inspection. The right thyroid lobe was cut open ex vivo in order to avoid spillage. A large 1.6 cm × 1.5 cm × 1.3 cm, oval-shaped lesion completely encased within the thyroid gland was found correlating with the USG and sestamibi scan, and this was confirmed using frozen section [Figure 3]. We opted not to explore the other side of the thymus in order to avoid unnecessary dissection. Serum iPTH and calcium levels became normal postoperatively.{Figure 3}

 Discussion



IPAs are the second most common cause of persistent hyperparathyroidism, after intrathymic adenomas.[6] True IPA occurred in only 0.7% of 10,000 primary cases, whereas another 1.2% were closely adherent to or partially within the thyroid substance.[7] IPA occurs in predictable locations within the thyroid gland, with the vast majority occurring in the lower lateral quadrant and a small percentage near the recurrent nerve and superior pole.[4],[7] The parathyroid gland occurs as an intrathyroidal variety when it becomes trapped within the thyroid as the lateral and medial lobes fuse. Although this is the common mechanism for both superior and inferior glands, the latter (derived from the 3rd branchial pouch) are pulled by the thymus during its descent, and because of migrating a longer distance, they have an increased chance of becoming entrapped during the fusion of the thyroid lobes.[8] Most useful investigations in the localization of IPA are USG and99m Tc-sestamibi scans.[9] According to a case series consisting of 53 patients with intrathyroidal parathyroid, sestamibi and USG correctly identified the adenoma in 35 (70%) and 11 (61%) cases, respectively.[10]

In USG, the main diagnostic difficulty lies in distinguishing IPA from thyroid nodules. The proposed USG criteria for identifying a parathyroid adenoma include solid composition, profound hypoechogenicity, and presence of a feeding polar vessel.[11],[12],[13] In a retrospective review, the sensitivity and specificity for differentiating an IPA from a thyroid nodule were 78% and 86%, respectively.[14] In sestamibi scan, likely error in diagnosis is because of errors in interpretation rather than errors in the scan itself.[15] Newer imaging modalities such as18 F-choline photon emission tomography/computed tomography can be very helpful in such cases, although this was not done in our case.[16]

Exhaustive literature review fails to provide enough evidence of a set protocol/extent of surgery for suspected IPA in general.[1],[4],[17] Goodman et al. believed that lobectomies are often performed indiscriminately in search of a missing parathyroid and are typically unsuccessful. As per their group, the missing gland can be found by careful dissection of the loose tissue surrounding the thyroid, thyroidectomy, or meticulous exploration of the lateral inferior lobe.[4] In our case, we opted for right thyroid lobectomy rather than indulging in thyroidectomy and enucleation based on other experiences to minimize the possibility of overlooking an IPA and avoid spillage (rupture of the capsule and parathyromatosis).[5],[17]

 Conclusion



The clinical pearls in a case of IPA are summarized in [Table 1]. IPA should be considered an important cause of PHPT. USG performed by an experienced sonologist and a correctly interpreted99m Tc-sestamibi scan are useful adjuncts to identify IPA preoperatively. Exhaustive literature review fails to provide enough evidence of a set protocol/extent of surgery for suspected IPA in general. However, preoperative identification and planning is of utmost importance to avoid unnecessary dissection. Thymectomy and bilateral neck exploration is not always necessary. Approach for every case should be individualized.{Table 1}

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient has given her consent for her images and other clinical information to be reported in the journal. The patient understands that her name and initial will not be published, and due efforts will be made to conceal identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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