Incidental Mediastinal Thyroid Cancer

A B S T R A C T

Cystic mediastinal masses are most commonly benign congenital lesions. Rarely, a cystic mediastinal mass will prove to be malignant. The patient, a 50-year-old woman who initially presented with uveitis, was incidentally found to have a right paratracheal opacity on chest X-ray (CXR). Chest computed tomography (CT) demonstrated a 5cm right paratracheal hypodense cystic mass. The patient underwent a right robotic-assisted thoracoscopic resection of the mediastinal mass. Final pathology revealed a 4.5cm mass consistent with metastatic papillary thyroid carcinoma (similar histology in 2 excised lymph nodes). The patient subsequently had a total thyroidectomy with central and right neck dissections.

Keywords

Mediastinal mass, thyroid cancer, thoracoscopy

Introduction

Cystic masses in the mediastinum are usually benign congenital lesions that represent as much as 30% of all mediastinal masses [1-3]. The differential diagnosis of mediastinal cysts includes esophageal duplication cysts, bronchogenic cysts, thymic cysts, pericardial cysts, enteric cysts, lymphangiomas, and even degenerated intrathoracic tumors [1-5]. Many patients will be asymptomatic from smaller mediastinal masses. As they grow, mediastinal masses typically cause local compressive symptoms such as dysphagia, dyspnea, or stridor. Here we present a case of an asymptomatic mediastinal cyst that was found to be metastatic papillary thyroid cancer (PTC).

Case Report

A 50-year-old woman presented with blurry vision and was diagnosed with uveitis. Her workup included a CXR which showed a right paratracheal opacity. Noncontrast-enhanced CT examination revealed a 5.0 x 4.0 x 4.9 cm right paratracheal hypodense mass that was not contiguous with the thyroid. The mass, which occupied the middle and posterior mediastinal compartments, began superiorly at the level of the thoracic inlet and displaced the esophagus to the left. Within the mass, areas of hyperdense debris, enhancing mural nodularity, and inferomedial curvilinear calcification were noted (Figure 1). The patient denied dyspnea, wheezing, chest pain, cough, hemoptysis, dysphagia, weight loss, or other symptoms referable to the mass.

Surgical resection was recommended. A right robotic-assisted thoracoscopic resection of the mediastinal mass was performed. Level 2R and level 3 lymph nodes were removed. The patient was discharged home on the first postoperative day without complications. The mediastinal cystic mass measured 4.5 x 3.5 x 1 cm. Histology confirmed metastatic PTC that was positive for ck7, TTF-1, thyroglobulin, and p63 (Figure 2). Level 2R and 3 lymph nodes showed similar findings. Approximately 6 weeks later, the patient underwent total thyroidectomy with central and right neck dissections. Pathology revealed multifocal PTC with metastases to right lateral level 2, 3, 4, and 5 lymph nodes as well as lymph nodes in the central compartment. There was extrathyroidal extension but no angioinvasion. The patient received postoperative radioactive iodine ablation, and she was started on thyroid hormone replacement therapy. The patient is doing well nine months post-operatively.

Discussion

The differential diagnosis for a cystic mediastinal mass depends on the compartment of the mass, patient presentation, and characteristics on imaging. Although PTC is the most common thyroid malignancy, its pathologic course includes early spread to local lymph nodes and rarely presents as a cystic mediastinal mass [6, 7]. Metastatic masses are usually solid, but up to 40% of affected nodes have the ability to centrally necrose and cavitate, forming a cystic lesion as seen in our case [7]. Previous case reports have documented the rare occurrence of PTC presenting as a symptomatic cystic mass in the mediastinum [7-9]. In our case, the patient presented with an asymptomatic mass found incidentally on CXR, consistent with a benign mediastinal cyst. Further workup yielded a diagnosis of PTC, lacking clinically evident thyroid or lymph node enlargement. Without a palpable lymph node, thyroid mass, or systemic manifestations of compression, a metastatic mass disguising itself as a cystic mediastinal lesion could easily lead to a delay in diagnosis. If not for the conscientious workup for uveitis, this patient’s thyroid carcinoma might have been missed, increasing the likelihood of overlooking anaplastic transformation [10].

Risk factors for PTC include ionizing radiation before the age of 20, Hashimoto’s thyroiditis, and familial adenomatous polyposis. PTC generally has a favorable prognosis with 98% 10-year survival. Favorable characteristics that portend a better outcome include younger age, female gender, and smaller tumor size. This case report highlights the value of accurate diagnostic imaging relative to mediastinal cysts. Histologic examination of an excised gross specimen is currently the standard for providing a specific diagnosis. However, diagnostic methods outside the standard should also be improved. Such optimization would improve decision-making regarding the evaluation and treatment of mediastinal masses. Currently, there is ongoing research on the accuracy of multidetector CT distinguishing between benign and malignant mediastinal masses [11]. In addition, new classifications of mediastinal compartments are being created to improve diagnostic accuracy [12]. Additional similar endeavors could help reduce the likelihood of falsely assuming the benignity of a mediastinal mass.

Conclusion

In this case, the asymptomatic presentation of PTC presenting as a cystic mediastinal mass highlights the importance of proper evaluation of these masses. Although most cystic mediastinal masses are benign, these lesions should not be overlooked. This case emphasizes the importance of optimizing diagnostic techniques outside histological examination as well as the importance of aggressive but appropriate surgical intervention. In this manner, one could reduce the chances of missing an atypical presentation of carcinoma.

Article Info

Article Type

Case Report

Publication history

Received: Mon 26, Aug 2019
Accepted: Tue 10, Sep 2019
Published: Tue 17, Sep 2019

Copyright

© 2023 Keith D. Mortman. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Hosting by Science Repository.
DOI: 10.31487/j.SCR.2019.04.13

Author Info

Keith D. Mortman Nicole Law Taraneh Hashemi-Zonouz

Corresponding Author

Keith D. Mortman
Division of Thoracic Surgery, Department of Surgery, The George Washington University Hospital, Washington, D.C.

Figures & Tables

Figure 1: Axial CT scan demonstrating 5.0 x 4.0 x 4.9cm right paratracheal cystic mass.

Figure 2: Thyroglobulin stain confirming thyoid origin (5x).

References

1. Oldham HN (1971) Mediastinal tumors and cysts. Ann Thorac Surg 11: 246-275. [Crossref]
2. Jeung MY, Gasser B, Gangi A, Bogorin A, Charneau D et al. (2002) Imaging of cystic masses of the mediastinum. Radiographics 22: 79-93. [Crossref]
3. Takeda S, Miyoshi S, Minami M, Ohta M, Masaoka A et al. Clinical spectrum of mediastinal cysts. Chest 124: 125-132. [Crossref]
4. Aydin Y, Araz O, Ozgokce M, Ince I, Alper F et al. (2015) Video-assisted thoracoscopic surgery of mediastinal cysts: Report of 13 cases. Indian J Surg 77: 236-9. [Crossref]
5. Martins C, Sousa P, Araújo T, Castro-Poças F, Pedroto I (2017) Mediastinal mass in a patient with colorectal cancer: A diagnostic challenge. GE Port J Gastroenterol 24: 193-197. [Crossref]
6. Wunderbaldinger P, Harisinghani MG, Hahn PF,  Daniels GH, Turetschek K et al. (2002) Cystic lymph node metastases in papillary thyroid carcinoma. Am J Roentgenol 178: 693-697. [Crossref]
7. Bhamidipati CM, Mukhopadhyay S, Feliu C, Patton B, Dexter E (2009) Cystic metastases of papillary thyroid carcinoma mimicking a primary mediastinal cyst. J Thorac Oncol 4: 105-106. [Crossref]
8. Suemitsu R, Takeo S, Hamatake M, Yamamoto T, Furuya K et al. (2010) Thyroid cancer with a cystic mediastinal tumor invading the right main bronchus. Ann Thorac Surg 89: 296-298. [Crossref]
9. Okumura M, Yasumitsu T, Kotake Y, Ohta M, Ohshima S et al. (1990) Three cases of occult thyroid cancer with mediastinal lymph node metastasis manifesting as a mediastinal cyst. Nihon Kyōbu Geka Gakkai Zasshi 38: 2307-2313. [Crossref]
10. Kim H, Park YW, Oh YH, Sim J, Ro JY et al. (2017) Anaplastic transformation of papillary thyroid carcinoma only seen in pleural metastasis: A case report with review of the literature. Head Neck Pathol 11: 162-167. [Crossref]
11. Pandey S, Jaipal U, Mannan N, Yadav R (2018) Diagnostic accuracy of multidetector computed tomography scan in mediastinal masses assuming histopathological findings as gold standard. Pol J Radiol 83: e234-e242. [Crossref]
12. Carter BW, Benveniste MF, Madan R, Godoy MC, de Groot PM et al. (2017) ITMIG classification of mediastinal compartments and multidisciplinary approach to mediastinal masses. Radiographics 37: 413-436 [Crossref]