Thymoma and thymic carcinomas are a type of cancer that affects the thymus, an organ located in between the breastbone and the heart. Thymus is a gland that functions to mature the T-cells which are the soldiers of the immune system and are very important to the body’s ability to adapt to and fight off new illnesses from various pathogens like bacteria, viruses and fungi.
Thymus gland is relatively large during infancy and reaches its full maturity around puberty after which the gland slowly involutes (becomes smaller in size).
In some people, the cells in the thymus gland can begin to grow abnormally and form tumours. These tumours can be a Thymoma or a Thymic Carcinoma.
Thymoma is a potentially malignant tumour of the thymus gland in which the cells bear resemblance to the original thymic cells. These grow slowly and rarely spread beyond the thymus gland. These tumours are further subdivided based on their cell characteristic ( which is known after biopsy or pathological examination of the removed tumour). So Thymoma can be further divided into Type A, AB, B1, B2 and B3 and C. Their aggressiveness increase in that order so Type A is least aggressive and Type C the most.
Thymic carcinoma on the other habd are composed of cells which are very different from thymic cells and are very aggressive and can spread to other body areas. In general thymic carcinoma is more difficult to treat than Thymoma.
Thymoma and thymic carcinoma may not cause early signs or symptoms.
• It may be detected incidentally during a routine chest x ray done for other reasons.
• A cough that doesn't go away.
• Chest pain.
• Trouble breathing
• Symptoms and Signs of Myasthenia gravis (click here to know more)
After a detailed history and physical examination the doctor may suggest certain tests to detect or confirm the presence of thymoma
A CT scan of the Chest
When a tumour of the Thymus gland that is Thymoma or Thymic Carcinoma is suspected a contrast enhanced CT scan of the Chest is usually the first investigation which will confirm the presence or absence of tumour.
Magnetic Resonance Imaging (MRI) of the chest may be required if there is doubt about the involvement of the underlying structures.
Whole Body PET Scan
In some cases a whole body PET scan may be required to rule out distant spread of the thymoma or thymic carcinoma beyond the confines of Thymus gland.
Routine blood investigations may be required to asses the patient’s fitness for undergoing treatment.
Apart from the routine investigations AChR-Antibody test may be ordered to look for myasthenia gravis
Certain other tests may be required to rule out conditions that may be associated with Thymoma like:
• Myasthenia gravis. (Click here to know more)
• Acquired pure red cell aplasia.
• Lupus erythematosus.
• Rheumatoid arthritis.
• Sjögren syndrome.
In stage I, cancer is found only within the thymus. All cancer cells are inside the capsule (sac) that surrounds the thymus.
Cancer has spread through the capsule and into the fat around the thymus or into the lining of the chest cavity.
Cancer has spread to nearby organs in the chest, including the lung, the sac around the heart, or large blood vessels that carry blood to the heart.
Stage IV is divided into stage IVA and stage IVB, depending on where the cancer has spread.
In stage IVA, cancer has spread widely around the lungs and heart.
In stage IVB, cancer has spread to the blood or lymph system.
Four types of standard treatment are used:
Thymomas are locally aggressive tumours and Surgery with complete removal of the tumour along with the thymus gland (Radical Thymectomy) wherever feasible is the best treatment ad offers the best chance for long term survival. So all patients with thymoma should be evaluated by surgeons who have lot of experience in operating on patients with thymoma. A common myth unfortunately prevalent in our country is that small thymomas are harmless tumours that can be left alone. This is not true and all thymomas no matter how small should be removed surgically in patient fit to undergo the procedure. That is because these are slow growing tumours and eventually will grow to large sizes and may involve adjacent structures as they grow making surgery difficult and more risky.
The surgery can be done by either open sternotomy (cutting through the breastbone) or by minimally invasive methods that include Video Assisted Thoracic Surgery (VATS) (Click here to know more) or by the state of art Surgical Robot (Robotic Thymectomy- Click here to know more). The advantage of minimally invasive techniques is that it avoids the cutting of the breast bone and therefore has lesser blood loss, lesser pain, earlier return to work and better cosmesis.
However not all tumours are amenable for minimally invasive surgery and patients need to be evaluated by an experienced surgical team for tailoring the best approach for an individual patient.
Some patients will require additional treatment with radiotherapy after surgical removal based on the characteristics of tumour found at surgery and the final stage of the tumour based on the final pathological report of the removed tumour. Even if the doctor removes all the cancer that can be seen at the time of the surgery, some patients may be given radiation therapy after surgery to kill any cancer cells that are left. Treatment given after the surgery, to lower the risk that the cancer will come back, is called adjuvant therapy.
Radiation therapy is a cancer treatment that uses high-energy x-rays or other types of radiation to kill cancer cells or keep them from growing. There are two types of radiation therapy. The way the radiation therapy is given depends on the type and stage of the cancer being treated. External radiation therapy is used to treat thymoma and thymic carcinoma either after surgery or for those patients as the primary treatment where an experienced surgical team deems the tumour unresectable.
Chemotherapy is a cancer treatment that uses drugs to stop the growth of cancer cells, either by killing the cells or by stopping them from dividing. The way the chemotherapy is given depends on the type and stage of the cancer being treated.Chemotherapy may be used to shrink the tumor before surgery or radiation therapy. This is called neoadjuvant chemotherapy.