Atypical presentation of a cystic parathyroid adenoma: Acute airway compromise secondary to intratumoral apoplexy - A case report

INTRODUCTION

Primary hyperparathyroidism is the common presentation of parathyroid adenomas. Parathyroid adenomas weighing >3.5 g and having a size of more than 2 cm are termed as giant parathyroid adenomas. Most adenomas are asymptomatic; however, giant adenomas can cause anatomical symptoms which can manifest as dysphagia, odynophagia, and dyspnea. Hemorrhage into a giant parathyroid adenoma is a rare presentation that can be life threatening due to acute airway compromise.^[1]

CASE REPORT

A 56-year-old female who has been a known diabetic for 8 years and hypothyroidism for 6 years, on medication, presented to the hospital with acute onset of breathlessness and stridor. She also has a history of anterior neck swelling for 2 years. Complete blood count and serum electrolytes were normal. Serum creatinine was 0.6 mg/dL. Serum calcium was 8.7 mg/dL and phosphorus was 2.8 mg/dL, free triiodothyronine - 2.7 pg/mL; Free Thyroxine - 1.32 ng/mL, and TSH – 3.7 µU/mL. The patient underwent non-contrast computed tomography neck and thorax on December 8, 2022. CT revealed multiloculated soft-tissue attenuation lesion with hemorrhage in post-cricoid region with extension into superior mediastinum. Fibro-optic laryngoscopy was performed on the same day and was normal.

The patient was planned for emergency bronchoscopy and tracheal stenting, but due to severe distress with glasgow coma scale score (GCS) drop, she was intubated and shifted to magnetic resonance imaging (MRI).

The patient underwent a contrast-enhanced MRI neck on December 9, 2022. MR images showed a well-defined multiloculated cystic lesion with blood-fluid levels in the lower neck in the post-cricoid region. The lesion was predominantly in the midline with right para-pharyngeal extension. The lesion was extending inferiorly to the superior mediastinum. Craniocaudally, the lesion extends from C4 to the D2 level. Mediolaterally, the lesion is seen between the carotid arteries posterior to the laryngeal airway; a small component of the lesion extends into the right lateral aspect of the neck, splaying the thyroid cartilage and jugular vein and lies immediately deep to sternocleidomastoid [Figure 1]. The lesion abuts the posterior wall of the trachea and esophagus and causes the displacement of the laryngeal airway anteriorly and to the left. The lesion is inseparable from the posterior aspect of the right lobe of the thyroid and esophagus. Posteriorly, the lesion abuts the anterior vertebral margin without any significant indentation. The lesion shows T1 intermediate and T2 hyperintense signals. Based on the patient’s age, imaging characteristics, and clinical history, the possibilities of venous-lymphatic malformation and esophageal duplication cyst with internal hemorrhage were considered as top differentials.

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Figure 1:

Axial T2-weighted (a and b) and fat-saturated images (c) of lower neck and upper mediastinum reveals a multiloculated T2 hyperintense lesion with blood-fluid levels which is posterior to the right lobe of thyroid and extending to superior mediastinum. T2 fat sat sagittal (d and e) and coronal (f and g) images shows the craniocaudal extent of the lesion with clear demonstration of the internal hemorrhage. T1 post-contrast axial (h) and sagittal (i) sections show peripheral rim of enhancement and clear demonstration of the relationship to the right lobe of thyroid.

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The patient underwent surgery and an excision biopsy of the cyst wall on December 10, 2022. The patient was discharged in stable condition on the 5^th postoperative day. In a histopathological and immunohistochemical examination of the surgical specimen, a cystic parathyroid adenoma with extensive hemorrhage was diagnosed [Figure 2].

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Figure 2:

(a) ×10 H and E shows multiple cystic space with hemorrhage lined by attenuated epithelium and on the left shows nest of parathyroid chief cells. (b) ×10 immunohistochemistry with pancytokeratin highlights epithelium lining cystic spaces. H and E: Hematoxylin and eosin.

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DISCUSSION

Cystic parathyroid adenomas account for a small proportion - 1–4% of all parathyroid adenomas.^[2] Parathyroid cystic adenomas are traditionally classified as functioning and non-functioning and may represent up to 5% of cystic tumors in the anterior region of the neck. Approximately, 90% of these are classified as nonfunctioning cystic lesions found in individuals with normal calcium concentrations.

Cystic parathyroid adenomas are associated with large lesions, high-serum levels of intact parathyroid hormone and calcium, a high risk of hypercalcemic crisis, and low accuracy of preoperative localization examinations. Current standard modalities for imaging parathyroid lesions include ultrasound, Tc99m-sestamibi, 4-dimensional CT, and MRI.^[3] The preoperative diagnosis of cystic parathyroid adenomas remains challenging. Combined ultrasound and Sestamibi scan has high diagnostic accuracy for solid adenomas, but the accuracy is low for cystic lesions.^[4]

Spontaneous parathyroid hemorrhage is a rare but potentially life-threatening complication of parathyroid disease. The possibility of hemorrhage in parathyroid lesions should be considered in anyone presenting with retropharyngeal or mediastinal hemorrhage, mainly if there is a documented history of hyperparathyroidism.

Nylen et al. proposed the classification of parathyroid apoplexy into

• Type I: Adenoma with necrosis without hemorrhage

• Type II: Adenoma with intracapsular hemorrhage and necrosis

• Type III: Adenoma with extracapsular hemorrhage.^[5]

Clinical presentations also vary in each group. The patient may be asymptomatic or experience gastrointestinal discomfort, cervical pain, tetany, and convulsions in adenoma with intracapsular hemorrhage.^[6] Acute pain, dysphagia, dysphonia, hoarseness, stridor, hypercalcemic crisis, widened mediastinum, visible hematoma, or ecchymosis may occur in patients with extracapsular hemorrhage. The definite treatment of parathyroid adenoma is surgical exploration.^[7]

DIFFERENTIAL DIAGNOSIS

1. Venolymphatic malformation.

2. Esophageal duplication cyst with internal hemorrhage.

CONCLUSION

Emergency intervention and neck exploration may be required in cases of airway compromise. In the literature, there is evidence that hemorrhage into the lesion leads to spontaneous remission of hyperparathyroidism. This phenomenon is referred to as auto parathyroidectomy/parathyroid apoplexy. The normal calcium levels in our case can be attributed to either non-functioning adenoma/phenomenon of auto parathyroidectomy.

TEACHING POINTS

1. Parathyroid apoplexy should be considered in any patient with spontaneous cervical hemorrhage which aids in pre-operative planning and avoidance of unnecessary delay in diagnosis and treatment.

2. Initial evaluation of patients with spontaneous cervical hemorrhage should include imaging, serum calcium, and PTH assay.

MCQs

1. What are the standard modalities for imaging parathyroid lesions

   1. Ultrasound

   2. Tc99m-sestamibi

   3. 4-dimensional CT

   4. MRI

   5. All of the above

   Answer Key: e

2. Which is the sensitive radiological modality in detecting solid parathyroid adenomas?

   1. Ultrasound and CECT

   2. CECT and CE MRI

   3. USG and MIBI scan

   4. MRI and MIBI scan

   Answer Key: c

3. Nylen classification of parathyroid apoplexy consists of

   1. 3 Types

   2. 4 Types

   3. 5 Types

   4. 6 Types

   Answer Key: a