Thyroid tumefactions that grow in the mediastinum are defined as intrathoracic goitres (retrosternal and intrathoracic are terms used interchangeably in the published literature) when the mediastinal portion is more represented than the cervical one and they overrun the thoracic inlet by two fingers below, or by at least 4 cm [1,2]^[1][2]. The prevalence reported in the literature is highly variable (0.1–21%) with a 10% average; the incidence occurs in about 1/5000 people and, as in other endocrine diseases, is more common in females than in males (F:M = 4:1) [3,4]^[3][4]. Retrosternal goitre can be divided into two types: “plongeant”, when the parenchymal tissue is connected to the thyroid gland and shares the vascularization (95–98% of cases), and autonomous (2–5% of cases), when this connection is not present and may be considered a mediastinal neoformation ^[5].

“Goitre plongeant” is technically challenging for surgeons due to the difficulties of mediastinum surgery. The mediastinum is usually divided into an anteroposterior direction by two virtual frontal planes. The first one is tangent to the anterior surface of the pericardium and great vessels, and the second is tangent to the anterior surface of the vertebrae. The middle compartment contains all of the vital structures and is significant in the surgical management of retrosternal goitre.

The use of prophylaxis with iodised salt and a greater use of the surgical approach reduce the incidence of large-sized goitres, although they are still found because of the conservative treatment preferred by endocrinologists due to the disease’s benign and asymptomatic nature ^[6].

2. Discussion of Retrosternal Goitre

Substernal goitre can be a challenging disease due to the mediastinal extension that brings it into close contact with vital structures. The advancement of diagnostic tools, such as CT or MRI, led to an increase in cases operated on in our department. The first period of surgery, from 1997 to 2007, included 60 patients (22.7%), while the second period, 2008–2021, included 2044 patients (77.3%). According to the literature, the presence of symptomatic retrosternal goitre and possible dimensional increase in asymptomatic young patients are both indications for surgery [11,12]^[7][8]. The dimensional increase could compress the oesophagus, trachea, recurrent laryngeal nerves, and vessels, necessitating an emergency surgical procedure. Elective surgery serves a therapeutic and preventive purpose, preventing neoplasm degeneration. Radioactive iodine treatment cannot achieve control of the disease and can also result in an acute inflammatory process that exacerbates clinical compression, potentially threatening the patient’s airway [3,4]^[3][4]. The starting point of the surgical procedure is the asportation of the largest part of the mass. If just one lobe is involved and the other is normal, surgery should consist of a hemi-thyroidectomy, minimizing the risk of complications while relieving symptoms of concern. If the dissection of the goitre from the laryngeal nerve or the vascular plane is not well-defined, a small portion of thyroid tissue should be left to avoid damage. Roman et al. identified key reasons for special attention to be paid in the preoperative laryngeal examination: the presence of vocal cord paralysis (VCP) may be clinically evident in the absence of dysphonic changes, and the presence of VCP influences the patient’s consent and counselling on the risks of potential surgery [10]^[9]. The choice of the surgical approach in a retrosternal goitre is a debated topic. In the literature, several authors claim that an isolated cervicotomy can completely remove the intrathoracic thyroid tissue [13,14,15]^[10][11][12]. According to Sormaz et al., a CT-volume in the mediastinal portion of a thyroidal mass greater than 162 cm³ and a craniocaudal length below the thoracic inlet greater than 66 mm are significantly associated with the need for an extra-cervical approach [16]^[13]. Furthermore, Huins et al. performed a review that included 34 studies and developed a three-grade system based on the substernal extension of the thyroidal mass: the first grade above the aortic arch, the second grade at the level between the aortic arch and the pericardium, and the third grade extending below the right atrium. They concluded that the sternal split, or sternotomy, is safer for thyroid glands in the second and third grades. Simo et al. reported four significant anatomical landmarks to detect high-risk patients, including the involvement of the carina of the trachea, the arch of the aorta, the pleura of the lungs bilaterally, and the oesophagus [17]^[14]. Cervicotomy was the gold standard in our series, and surgical success was achieved in 96.6% of cases. WThe researchers also used it as the starting point to explore the goitre and its boundaries and to proceed with the dislocation of the mass using the connection between the thyroid lobe and the mediastinal portion. This is made feasible by the process of migration of the mediastinal portion, which maintains the vascularization shared with the cervical segment. Furthermore, weresearchers should mention that cervicotomy presented a lower rate of post-surgery complications than combined access (p-value < 0.01) and a shorter length of stay (p-value = n.s.). Some authors claim that bleeding is a life-threatening condition that is difficult to control only with cervical access [18]^[15].  Furthermore, most of this bleeding occurred within the first 8 h of surgery and was accompanied by coughing fits. It can lead to laryngeal oedema and potential airway obstruction, including death [17,18]^[14][15]. The success of the surgical strategy is based on some stratagems. First of all, the patient’s position should not be excessively hyper-extended to avoid the contraction of the neck’s ribbon-like muscles, thus causing a difficult dissection. The second important stratagem is to perform a broad and low cervicotomy (on the clavicular line), extending the distal opening of the linea alba to the retrosternal insertion of the pre-thyroid muscles, and their subsequent detachment from the sternocleidomastoid. If necessary, a partial or total section of the pre-thyroid muscles is a useful way to stretch the thyroid loggia and make space for the cleavage. After ligating and dissecting the middle vein (if any, and if accessible), and then the superior peduncle, the strict plane of the extracapsular dissection guarantees a gradual finger dissection. It is recommended that the inferior thyroid artery is ligated close to where it originates at the trunk as a preventive measure to ensure haemostatic control, or in the event that it interferes with the luxation of the sunken portion, and the digital identification of the recurrent laryngeal nerve, which is sometimes displaced posteromedially to the goitre and fused with the capsular plane. At the end, if possible, searching for the sub-isthmus trachea and follow it into the mediastinum to locate the goitre’s dissection plane, starting from the side that is less affected. Externalising the goitre with the index finger to pull the plongeant portion. If this blind manoeuvre is difficult to achieve, wresearchers consider it useless to only proceed with cervical access because it can cause a dangerous vascular lesion. WeThe researchers recommend using combined access or another type of access when it is impossible to reach the lower margin of the plongeant goitre with a digital dissection and when it is impossible to remove the mediastinal portion from the thoracic inlet or to separate it from the mediastinal structures due to an inflammatory or neoplastic process. A high degree of kyphosis, vein stasis due to the compression of the mediastinal vein, and emergency situations are all cases where combined access should be used [3,4]^[3][4]. Sternotomy enables the removal of the retrosternal goitre, which would otherwise be difficult to explore safely through cervicotomy due to the nature, shape, dimension, site, and boundaries with other mediastinal structures. In accordance with the literature, the gold standard of access in this situation is partial or total sternotomy that performed in 6 patients (Figure 31). The indications are goitre plongeants with large dimensions, those that are symptomatic, prevascular, or retrovascular on the left side, those that are difficult to remove, and those with neoplastic degeneration in the mediastinal portion [19,20]^[16][17]. Combined access in the form of thoracotomy and cervicotomy is rare (only two cases in our initial experience). Anterior thoracotomy is easy to perform, but it is difficult to obtain a view of the right recurrent laryngeal nerve. Thoracotomy is not recommended if the mediastinal portion is developed on the left side, due to the presence of the sovra-aortic vessels. Posterolateral thoracotomy prolongs surgical time due to the change in position. Indications include a large posterior goitre on the right side, with suspected malignant degeneration, and thoracic structural adhesions [21]^[18]. The primary target is the removal of mechanical obstacles and the prevention of future compressive symptoms, especially in young people [22]^[19]. This pathology should also be treated in a referral centre in order to ensure optimal results and low morbidity rates and complications; ability, experience, profile, availability of experienced personnel, and proper materials must not be underestimated [23]^[20]. The surgical team’s experience is another crucial factor in ensuring surgical success, despite the obstacles associated with the goitre’s dimension and location.