What are thymoma and thymic carcinoma?

It is a rare tumor and is seen in approximately 1-1.5% of all cancers. Thymus tumors are tumors of the thymus gland located in front of the heart and great vessels behind the anterior mediastinum of the chest, behind the sternum.

Thymic tumors are a broad nomenclature, but thymoma and thymic carcinoma are the most common types that develop from differentiation of the thymic epithelium.

— Thymoma can be seen at any age from 8 months to 90 years, the average age of occurrence is between 40-60 years (Mean age is 53 years). The incidence in men and women is approximately equal.

— 95% of thymomas are located in the anterior mediastinum.

What symptoms can thymomas show?

—-Thymoma patients often do not show clinical symptoms.

—- Approximately 30% of patients are asymptomatic, while 30-44% show paraneoplastic disorders such as MG. —Local symptoms; pain, cough, hoarseness and dyspnea, superior vena cava (SVC) syndrome (swelling of the face, neck, and arms) are seen in some cases.

—- Other paraneoplastic syndromes in 2-5% of patients; They may be associated with these tumors, with pure red cell aplasia and hypgammaglobulinemia being the most common. The mechanism of onset of non-MG syndromes is still unclear. After MG, the most common are red cell aplasia and other immune diseases accompanied by hypogammaglobulinemia.

How are thymomas diagnosed and diagnosed?

— It usually occurs by chance and is detected during a control during another disease.

—The diagnosis of thymoma is usually made on the basis of symptoms and radiological imaging, if present.

— Detected earlier in patients with Myasthenia Gravis (MG)

— Radiologically: PA Lung and lateral X-ray, Thoracic tomography (CT), MRI, PET CT examinations are performed, but always tissue diagnosis is required.

— Invasive diagnostic methods: Fine-needle aspiration biopsy may be helpful in diagnosis, but it is insufficient to identify subtypes. Tru-cut biopsy can improve sensitivity and specificity and definitive diagnosis. Larger tissue samples can be obtained by anterior mediastinotomy, VATS, and mini-thoracotomy.

Cell type and staging in thymomas

— The histological classification of thymic tumors is one of the most controversial issues in pathology. These lesions are often encapsulated. However, some may show the same typical histological features as invasive thymomas and those that tend to recur.

— Recurrence and metastases are observed even in Stage I and every histological subtype, but it has been shown that recurrence is less in medullary and type A tumors. Therefore, histology should be paired with staging when assessing prognosis.

—Type A Thymoma refers to spindle cell and medullary thymoma. It is relatively rare compared to others and constitutes 4-19% of thymic tumors. It occurs in elderly patients and 20% of cases are associated with MG. It usually coincides with Masaoka Stage 1.

— Type AB Thymoma TYPE AB thymoma is a mixed tumor.

— Type B Thymoma Type B is divided into 3 subtypes. Type B1 thymoma; Type B2 thymoma; Type B3 thymomas (formerly classified as well-differentiated thymic carcinoma) contain medium-sized round or polygonal cells with predominantly mild atypia. These tumors are more aggressive than B1 and B2 thymoma. Metastasis and recurrence are not uncommon.

— Type C Thymoma Type C thymoma (previous thymic carcinoma) accounts for less than 10% of thymic tumors and is not usually associated with MG. Depending on the stage, grade, and histology, type C thymoma has a worse prognosis.

WHO classification system. Type A Spindle cell thymoma, medullary thymoma Type AB Mixed thymoma | Type B1 Lymphocyte rich thymoma, lymphocytic thymoma, cortex dominant thymoma Type B2 Cortical thymoma Type B3 Well differentiated thymic carcinoma, epithelial thymoma, squamoid thymoma Type C Thymic carcinoma (heterogeneous)

Staging

The staging system was originally used for thymoma first, but is now also used for thymic carcinoma. This classification system; It is a system based on local invasion, distant intrathoracic (inside the rib cage) and extrathoracic (outside the rib cage) metastases. Metastatic spread is relatively rare, predominantly intrathoracic. Extrathoracic and lymphogenous metastases are extremely rare, and it is unusual to be seen at the time of diagnosis.

KOGA Staging system

Koga modification of the Masaoka staging system

Stage 1 Macroscopically and microscopically completely encapsulated

Stage 2 A Microscopic transcapsular invasion

Stage 2 B Macroscopically, there is invasion of the surrounding mediastinal fatty tissue (no invasion into the mediastinal pleura)

Stage 3 Adjacent organ invasion

Stage 4 A Pleural or pericardial spread

Stage 4 B Lymphogenous or hematogenous metastases

TNM staging system

T1 Macroscopically completely encapsulated and no microscopic capsule invasion

T2 Macroscopic adhesion or invasion into surrounding fatty tissue or pleura, microscopic invasion into adjacent organs such as large vessels, pericardium, or lungs

T3 Invasion of adjacent organs such as large vessels, pericardium, and lungs

T4 Pleural or pericardial spread

N0 No lymph node metastases

N1 Metastasis to anterior mediastinal lymph nodes

N2 Intrathoracic lymph node metastasis outside the anterior mediastinal station

N3 Extrathoracic lymph node metastasis

MO No distant metastases

phase	T	N	M
Stage 1	T1	N0	M0
Stage 2	T2	N0	M0
Stage 3	T3	N0	M0
Stage 4a	T4	N0	M0
Stage 4b	Any T	N1-3	M0
	Any T	Any N	M1

Treatment success in thymoma tumors depends on what?

—The cell type of the tumor and the stage of the tumor are the most important prognostic factors for thymic tumors;

— Complete surgery is an important prognostic factor; Even in advanced stage patients, the risk of recurrence is lower after complete resection.

— Tumor size is another important prognostic factor

— Coexistence with MG was believed to be a poor prognostic factor. However, now the presence of MG is no longer considered a poor prognostic factor, and most recent studies have shown significantly better survival in the MG group. This is probably because more patients with MG are diagnosed at stages 1 and 2.

— Other thymoma-related syndromes that affect mortality and morbidity include dermatopolymyositis, inflammatory bowel disease, pernicious anemia, scleroderma, rheumatoid arthritis, and amyloidosis.

— Although lymph node involvement is a poor prognostic factor; This rare involvement is not an ideal marker for survival.

— Large vessel involvement (stage 3) is an independent prognostic factor

— Recurrence, that is, recurrence of the disease, is stated as a poor prognostic factor.

Surgical treatment in thymoma (thymus tumors)— Surgical approach techniques Open surgery (thoracotomy or sternotomy) Minimally invasive methods (Surgeries with small incisions)

Videothoracoscopic Surgery

Robotic surgery |

—Complete resection is the gold standard treatment for full cure. — Removal of the entire thymus tissue together with the surrounding mediastinal fatty tissue as a block is very important, especially for patients with MG.

Recurrent Tumors (Recurrent tumors)

— Intrathoracic recurrences; It can occur in the pericardium, pleura, mediastinum and lung parenchyma. 50-75% of relapsed patients are operable, complete resection is possible in 45-70% of cases.

—The 5-year survival rate is 72% in complete resection and 0.25% in incomplete resection. Up to 13 years disease-free after relapse surgery has been reported. A second recurrence after complete resection is seen in 16-25%, but at this stage the surgery should be interpreted as part of the multimodal approach.

Oncological treatment of thymomas

— Chemotherapy

Although the response of combination therapies is higher; The single agent regimen has also been shown to be effective in recurrent, metastatic and locally advanced diseases.

—Thymomas are sensitive to many drugs. With combined drug treatments, the mass can be reduced, it has been shown to provide palliation of symptoms.

— Radiotherapy

— Thymic tumors usually respond well to radiotherapy. For this reason, RT is often considered part of adjuvant therapy protocols.

— Stage 1 tumors do not require additional treatment after complete resection.

— Stage 2B lesions, especially B2, B3 and C tumors, have an increased risk of recurrence.

— Recurrence was 0% in those who received adjuvant RT, while this rate was 36.4% in those who did not receive RT.

— Strong evidence is shown of the need for postoperative RT in stages 3 and 4.

— Many studies have shown that recurrence does not develop after postoperative RT after complete resection.

— In stage III or IV disease with incomplete resection, adjuvant radiotherapy has shown that the residual recurrence rate is reduced.

— Neoadjuvant RT is rarely used, but it is mostly applied to perform RO resection in locally invasive cases.

Rekürren Tümörler (Nüks eden tümörler) — İntratorasik nüksler; perikard, plevra, mediastinum ve akciğer parankiminde ortaya çıkabilir. Nüks eden hastaların %50-75’i operabıldır, vakaların %45-70’inde komplet rezeksiyon mümkündür. —Komplet rezeksiyonda 5 yıllık sağ kalımı %72’ken inkomplet rezeksiyonda %0 25’tir . Nüks cerrahisi sonrasında hastalıksız 13 yıla kadar süre rapor edilmiştir . Komplet rezeksiyon sonrası ikinci rekürrens %16-25 oranında görülür, ancak bu aşamada ameliyat multimodal yaklaşımın bir parçası olarak yorumlanmalıdır.