Robotic Ectopic Thyroid Resection Presenting as an Anterior Mediastinal Mass

There is close to a consenus regarding the surgical management of anterior mediastinal masses for the great majority of cases. However, there is continuous debate regarding the surgical approach to achieve optimal results. Therefore, we present a robotic strategy to achieve complete resection of a huge anterior mediastinal mass in a rare presentation of ectopic thyroid tissue.

We present the case of a 51-year-old female who sought medical care due to symptoms of breathlessness and a retrosternal compression sensation during decubitus. She had no signs of muscle weakness, eyelid ptosis, or diplopia. The only medical record of note was a left thyroidectomy within the past 10 years due to a benign nodule, with normal hormonal function without need of exogenous reposition. After a mediastinal enlargement on the x-ray, we proceeded to a CT scan and an MRI that reported a heterogeneous lesion with intervening cystic degeneration, intense contrast enhancement, measuring 5, 6x4, 6x6, 3 cm, and intimate contact with the brachiocephalic vein.

A multidisciplinary board discussed the case and determined the need for surgical resection. The patient was submitted to robotic-assisted thoracoscopic surgery (RATS) using a Da Vinci Xi® surgical platform (Intuitive Surgical, Inc., Sunnyvale, CA) with three ports of 8mm for the robotic arms and one 15mm port for the assistant on a left-side approach.

The surgery began by opening the mediastinal pleura just above the phrenic nerve in a counterclockwise dissection, using a bipolar Maryland in the right hand. Due to the difficulty in identifying the innominate vein, we proceeded with an intravenous application of indocyanine green to use the Firefly™ function and properly localize the highlighted vein. After dissecting and isolating the innominate vein and controlling the internal mammary vein with a hemoclip, we proceeded with the surgical dissection of the tumor by using the pericardium as the posterior limit. Moving forward, the thymus was identified above the mass without any relationship with it, suggesting that it was a tumor of non-thymic origin. The complete tumor resection with the adjacent thymus tissue was completed uneventfully by the left robotic approach. The tumor was withdrawn from the chest cavity through a little enlargement (5 cm) of the accessory port without the need of a rib retractor.

The final anatomopathological result was ectopic thyroid tissue with no malignancy and adjacent thymic tissue with normal architecture for the age. The patient had a favorable recovery and was discharged on the 2nd post-operative day.

The ectopic thyroid is defined as any thyroid tissue not found on the anterolateral tracheal space of the 2nd to 4th tracheal rings. It is a rare condition, corresponding to less than 1% of all mediastinal masses (1, 2). More frequent in euthyroid females, it can be discovered in any location along the developing embryonic thyroid going through the foramen cecum to the habitual pre-tracheal location. The majority of patients are asymptomatic; however, some may present with compression-like symptoms when surgical resection is the standard treatment (3). The gradual and progressive robotic platform implementation for thoracic surgery is revolutionary with regard to the treatment of anterior mediastinal masses. The conversion rate is near to 0%, compared to 3-5% for the videothoracoscopic approach. Also, the rate of R0 resection and the long-term oncological results are comparable to open access by median sternotomy, with a shorter length of stay and better recovery (4, 5).

This case is a great example of a rare presentation of ectopic thyroid tissue. It demonstrates the safety and efficiency of the robotic platform in the treatment of big mediastinal masses.

References

1. Roh E, Hong ES, Ahn HY, Park S-Y, Yoon HI, Park KS, et al. A case of mediastinal ectopic thyroid presenting with a paratracheal mass. Korean J Intern Med. 2013;28(3):361.
2. Regal M, Kamel MM, Alyami H, AL-Osail EM. Mediastinal ectopic thyroid mass with normal thyroid function and location: Case report. Int J Surg Case Rep. 2018;52:5–7.
3. Guimarães MJA da C, Valente CMS, Santos L, Baganha MF. Tireoide ectópica no mediastino anterior. J Bras Pneumol. 2009 Apr;35(4):383–7.
4. Kang CH, Hwang Y, Lee HJ, Park IK, Kim YT. Robotic Thymectomy in Anterior Mediastinal Mass: Propensity Score Matching Study With Transsternal Thymectomy. Ann Thorac Surg. 2016 Sep;102(3):895–901.
5. Savitt MA, Gao G, Furnary AP, Swanson J, Gately HL, Handy JR. Application of Robotic-Assisted Techniques to the Surgical Evaluation and Treatment of the Anterior Mediastinum. Ann Thorac Surg. 2005 Feb;79(2):450–5.

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