What Is a Toxic Goiter?

Intrathoracic goiter is a simple goiter or thyroid tumor behind the sternum or mediastinum. Because it is not easily found behind the sternum or in the mediastinum, it brings certain difficulties to diagnosis and treatment. Intrathoracic goiter, like neck goiter, is a multiple nodular non-toxic benign thyroid tumor. Sometimes the benign and malignant tumors and the tumor and nodular hyperplasia are difficult to diagnose before surgery. Intrathoracic goiters account for 9% to 15% of thyroid diseases, with more women than men. The clinical manifestations are caused by the compression of the surrounding organs by the mass.

Basic Information

nickname

Falling intrathoracic goiter, primary or vagus intrathoracic goiter

English name

struma endothoracica

Visiting department

Thoracic Surgery

Multiple groups

More women than men, mostly over 40

Common causes

Caused by the thyroid tissue remaining in the mediastinum of the patient's embryo

Common symptoms

Hunchback, short neck, obesity, difficulty breathing, wheezing, difficulty swallowing, esophagus is softer than trachea, etc.

Causes of intrathoracic goiter

The intrathoracic goiter was originally a cervical goiter, located between the two deep fascias on the front of the neck, and was restricted by the anterior cervical muscles on both sides. Due to the effect of the thyroid's own gravity, it gradually dropped into the entrance of the thorax and was attracted by the negative pressure in the chest. Partial or complete fall of the normal or enlarged thyroid into the posterior sternum space, so it can also be called fall into the thorax. According to the degree of fall, it can be divided into partial type or complete type.

Intrathoracic goiter without any connection with surrounding tissues can also be called primary or vagus intrathoracic goiter. It is caused by the thyroid tissue remaining in the mediastinum of the patient during the embryonic period and develops into a thyroid tumor. Its blood supply comes from the chest. The internal blood vessels are mostly located in the middle and posterior mediastinum, and the lower mediastinum only accounts for 10% to 15%, and a few can approach the level of the diaphragm.

Clinical manifestations of intrathoracic goiter

Intrathoracic goiters account for 9% to 15% of thyroid disease and 5.3% of mediastinal tumors. There are more women than men, and the ratio of men to women is 1: 3 to 4, mostly over 40 years old.
Patients often have varying degrees of hump, short neck, obesity, and some patients have a history of thyroid surgery. Asymptomatic patients account for about 30%. The clinical manifestations are caused by masses that compress the surrounding organs. If the trachea is compressed, it causes breathing difficulties and wheezing; compression of the superior vena cava can cause superficial vena cava irritation of the upper chest and neck, and edema of the upper limbs; compression of the esophagus causes difficulty in swallowing. The esophagus is softer than the trachea. Even if the esophagus is compressed or displaced, it can still avoid the pressure of the tumor. The above symptoms rarely occur. The severity of the symptoms is related to the size and location of the mass.

Compression symptoms appear only when the intrathoracic goiter is simply enlarged, the posterior sternum space is narrow, and even if the tumor is small, symptoms can appear early.

Individual patients have acute dyspnea due to a mass embedded at the entrance of the thorax or spontaneous, traumatic bleeding. In severe cases, long-term compression of the trachea by the tumor causes softening and even suffocation. These symptoms can be exacerbated when lying on your back or moving your head to the affected side. If there is hoarseness and loss of voice, it is often caused by malignant tumors compressing the recurrent laryngeal nerve, and benign intrathoracic goiter is very rare to compress the recurrent laryngeal nerve. Horner syndrome is caused by the tumor descending to the posterior mediastinum and compressing the sympathetic nerve. It is rare. If accompanied by palpitation, shortness of breath, night sweats, high blood pressure, etc., hyperthyroidism is indicated.

Intrathoracic goiter can be partially or completely located in the thorax, and is divided into two types according to the source of its generation:

Retrosternal goiter

It is located in the anterior mediastinum and has a direct connection with the neck thyroid, also known as secondary retrosternal goiter. Its blood supply mainly comes from the inferior thyroid artery and its branches.

2. True intrathoracic goiter

Most are located in the visceral mediastinum. After entering the thoracic cavity, it is located inside and behind the large blood vessels and is close to the trachea. This type of intrathoracic goiter is only connected to the neck thyroid with blood vessels or fibrils. Its blood supply is derived from intrathoracic blood vessels and is rare.

Physical examination: Falling intrathoracic goiter can touch the enlarged thyroid in the neck and extend into the chest without touching the lower pole. Patients with previous history of thyroid surgery and complete retrosternal goiter have difficulty touching the lump in the neck. Physical examination should distinguish the relationship between cervical thyroid and intrathoracic thyroid, the relationship between tumors and swallowing activity, the condition of the lower boundary, and the extension of thyroid tumors into the chest.

Intrathoracic Goiter Examination

1. When combined with hyperthyroidism, serum T ₃ and T _{4 may} increase and TSH decrease.

2. Chest X-ray

(1) When the posterior sternum goiter is small, the mediastinal shadow does not widen, it can be seen that the density of the upper mediastinum is slightly higher, and the trachea can often be compressed. The existence of the tumor can be inferred by the curved impression of the trachea. After the tumor has enlarged, the upper mediastinal shadow can widen to one or both sides. If the tumor occurs in the right lobe, the mediastinal shadow protrudes to the right, and the larger one may protrude slightly to the left. If it occurs in the left lobe, when the tumor is small, the shadow protrudes to the left only. Protruding sideways. If the tumor occurs on both sides or the isthmus, the mediastinal shadows protrude to the sides. Because the aortic arch is relatively fixed and has a greater resistance to tumor pressure, the mediastinal shadows protrude mainly to the right, while the enlarged thyroid can compress the aortic arch to the lower left.

(2) When the goiter is large, it can compress the trachea to shift it to the opposite side and the back; if it is located behind the trachea, it compresses the trachea to shift it to the front and the opposite side. The curvature of the trachea is large, often extending all the way to the neck and ending at the throat. This phenomenon is strong evidence of goiter.

(3) The shadow of the posterior sternum goiter is connected with the soft tissue of the neck. On the radiograph or X-ray film, it can be seen that the tumor shadow of the upper mediastinum extends to the neck. Based on this, it can be distinguished from other mediastinal tumors. Because the mass is often closely connected to the trachea, there is an upward movement during swallowing. Without this movement, the possibility of this disease cannot be completely ruled out.

(4) The esophagus can be displaced to the left or right by compression. Occasionally, the tumor can be embedded between the esophagus and the trachea to widen the gap between them. If the esophageal mucosa is damaged, it is a malignant tumor.

(5) The edges of benign thyroid tumors may be slightly lobulated, and malignant tumors are wavy. The density of tumor shadows is uniform, sometimes calcified, lumpy or spotted, and arced at the edges. However, the presence or absence of calcification cannot be used to identify benign and malignant tumors. Malignant tumors can metastasize to the lungs or bones.

(6) The mediastinal inflatable angiography can make the thyroid tumor clear. The cross-sectional tomography examination shows that the mass is located in front of the aorta.

3.CT inspection

The typical manifestations are as follows: connected to the neck thyroid, located in the anterior tracheal space, and can also extend behind the trachea and esophagus; the boundary is clear; with a little, ring-shaped calcification; the mass is mostly a substantial shadow, Uneven density, accompanied by low-density areas that are not enhanced; accompanied by tracheal displacement, compression, esophageal compression, etc .; CT value is higher than surrounding muscle tissue. It is usually 50 to 70 HU, sometimes up to 110 to 300 HU, and the CT value of the cystic region is 15 to 35 HU.

4.B ultrasound, MRI and DSA

B ultrasound can determine whether the mass is cystic or solid. MRI can understand the relationship between the mass and surrounding large blood vessels, and exclude the possibility of hemangiomas. DSA understands the source of blood supply to the mass and the blood circulation of the mass itself.

5. Radionuclide

¹³¹ I examination can determine whether the mass is thyroid tissue, can also determine its size, location, or the presence of thermal nodules secondary to hyperthyroidism.

Intrathoracic Goiter Diagnosis

Intrathoracic goiters and tumors are more common in women. Diagnosis can be made based on medical history, clinical manifestations, and auxiliary examinations such as CT.

Differential diagnosis of intrathoracic goiter

Hemangiomas

If the intrathoracic goiter protrudes to the upper right, it should be distinguished from an anonymous aneurysm and zygomatic vein lobe; when it protrudes to the left mediastinum, it should be distinguished from aortic aneurysm. Anonymous aneurysm does not move upward when the patient swallows, and sometimes pulsations can be seen under perspective. Echocardiography checks that the pulse is synchronized with the aortic wave. Can cause rib damage, if necessary, angiography. Pulmonary texture can still be seen in the veins of the odd veins, and weird odd veins can be seen near the hilum, and the trachea is not compressed. If necessary, a tracheobronchiogram was performed. The aortic aneurysm often raises the aortic arch and shifts upwards; the retrosternal goiter causes the aortic arch to shift downwards to the left. The aortic aneurysm is accompanied by dilation of the other aorta and enlargement of the heart. If necessary, wave or aortic angiography can be performed. In addition, syphilis is more common in aortic aneurysms or anonymous aneurysms, and those with a positive Hua-Kang response should be considered aneurysms first.

2. Neurogenic tumors

Intrathoracic goiters should be distinguished from neurogenic tumors when they are located in the posterior superior mediastinum.

3. thymoma

Thymoma is located in the anterior mediastinum, but is located lower than the intrathoracic goiter. It is often associated with myasthenia gravis, simple red cell line hypoplasia, hypogammaglobulinemia and other associated tumor symptoms.

Intrathoracic Goiter Treatment

Intrathoracic goiters often have symptoms of compression, and some of them have secondary hyperthyroidism. Their malignant tendency is large. Once diagnosed, intrathoracic goiter and thyroid tumor resection should be performed as soon as possible. The surgical method varies depending on the location, depth, shape, size of the mass and its relationship with surrounding organs. For those with secondary hyperthyroidism, antihyperthyroidism should be treated before surgery.

Anesthesia choice

According to different surgical incisions: Cervical plexus anesthesia or local anesthesia is suitable for lower neck incision of neck and smaller tumor. The patient is awake during the operation, and can cooperate with swallowing and insufflation to make the tumor easy to lift and facilitate the operation. It can talk with the patient and prevent damage to the recurrent laryngeal nerve. General anesthesia is suitable for patients with large masses, deeper locations, completely inside the chest, and difficulty breathing. Preoperative X-ray films confirmed tracheal compression, displacement, and superior vena cava compression, with hyperthyroidism. During the operation, oxygen supply can be guaranteed, the airway can be kept unobstructed, and the stability of the respiratory and circulatory systems can be guaranteed.

2. Incision selection

According to the relationship between the tumor and the cervical thyroid, whether the tumor is partly or entirely located in the thorax, where the tumor is located in the mediastinum, and the tumor's invasion or compression of surrounding organs, the following incisions can be selected:

(1) Low neck collar incision is suitable for most of the falling intrathoracic goiters located in the posterior superior mediastinum of the sternum, which can be removed through this incision.

(2) Low-neck neck incision plus midline split of sternal bone Applicable to huge fall- throat goiter, which cannot be pulled out from the sternum entrance; fall-down goiter, lower position and partial blood supply Those from the chest; those with suspected malignant changes; those with a history of neck surgery who have difficulty with scar adhesion surgery; those with superior vena cava syndrome, or those with significant compression and deformation of the trachea who have wheezing.

(3) Chest incision Applicable to vagus intrathoracic goiter without a neck mass or with an unclear diagnosis; a posterolateral incision can be used for those whose thyroid mass is clearly located in the posterior mediastinum before surgery.

(4) Combined cervical and thoracic incision The indication is basically the same as that of thoracotomy, but it can reduce the damage to the lower thyroid artery and recurrent laryngeal nerve.

3. Common complications and prevention

(1) Injury of the recurrent laryngeal nerve during the operation. Any incision during the operation should be separated from the thyroid capsule. If you are performing cervical plexus anesthesia, you should talk to the patient during surgery to avoid recurrent laryngeal nerve injury.

(2) Postoperative tracheal compressive asphyxia due to hemorrhage . The stump of the thyroid should be overlapped with sutures during surgery. At the end of the surgery, a negative pressure suction was routinely placed in the wound to drain bleeding from the wound in time, and it was easy to observe whether there was active bleeding.

(3) Trachea collapse or stenosis Large fall-down intrathoracic goiter long-term compression of the trachea can make the trachea prolonged and deformed. When it is found that the trachea wall is softened during surgery, it should be sutured with the anterior cervical muscle group to prevent Postoperative trachea collapsed or narrowed. If symptoms of acute respiratory obstruction occur, a tracheotomy should be performed immediately to ensure that the airway is unobstructed.

4. Postoperative adjuvant therapy

Intrathoracic thyroid malignancies are not completely removed. Residual lesions should be marked. Postoperative radiotherapy should be performed. The amount of radiotherapy should be 55 to 65 Gy. Intrathoracic goiter is the same as cervical goiter. After complete bilateral resection, thyroid hormone tablets must be taken for a long time. If it is a malignant thyroid tumor, thyroid hormone tablets should also be taken after surgery. The effect is good.

Prognosis of intrathoracic goiter

If the intrathoracic goiter is a benign lesion, the effect of surgical resection is good, and the chance of recurrence after surgery is small; if it is malignant, the main factors affecting the prognosis are: complete resection, pathological nature and type of tumor. Those who can be completely removed by surgery have a good prognosis, with a 5-year survival rate of 64.7% and a 10-year survival rate of 46.7%. Papillary adenocarcinoma has a good prognosis, with no significant difference in 5-year and 10-year survival rates; those with incomplete surgical resection have a high chance of recurrence and metastasis after surgery, and the prognosis is still good after supplemental radiotherapy, and a few patients can survive for a long time.