The thymus is a small fatty gland just behind the breastbone, in front of the heart and between the edges of both lungs. It is the home of part of the developing immune system in infancy and childhood but is not important in adults.  Usually as we get older it shrinks and is mainly replaced with fat, but sometimes it is involved in various diseases.

Benign Thymic Diseases

Sometimes it develops pockets of fluid called thymic cysts, which can press on the heart or lungs and which can become infected. Surgery is usually recommended to remove these cysts or if bacterial infection spreads to the gland.
In the rare condition called myasthenia gravis, the thymus is involved in an auto-immune condition where antibodies damage the link between the nerves and muscles, leading to fatigue and muscle weakness. When the condition is difficult to control with medication, surgery can be performed to remove the thymus and often improves the condition. In addition, around 20% (1 in 5) of patients with myasthenia may develop a thymoma, a growth or tumour in the gland, which again would be a recommendation for surgical removal.

Thymic Tumours

Benign Thymoma: This rare but benign growth can develop on its own but is more common in patients with myasthenia gravis. It does not usually cause problems unless it is large enough to press on the heart or lungs. It is usually discovered as an incidental finding when people have a chest scan for other problems like Covid.

Thymic Teratoma: This rare tumour is usually benign but can have malignant components. Cells grow and duplicate tissues of many different organ types from around the body, such as fat, hair, skin, thyroid, sometimes even teeth!

Thymic Carcinoma: These are rare cancers of several types that arise in the cells of the thymus gland. In general, these are similar to the range of types of lung cancers although they are not from the lung. It is possible for them to spread around the chest or the rest of the body and they can grow rapidly to invade the lungs and vessels and other nearby tissues.

Treatment of Thymic Tumours

If there is any doubt about the diagnosis of a mass in the chest, several types of scans – CT, PET or MRI may be recommended. A guided biopsy may be needed to rule out diseases like lymphoma that do not need surgery. However, surgical removal is usually recommended for any thymic tumour that is able to be removed safely. Even in benign tumours, malignancy (cancer) can develop if they are left for a long time and cannot be excluded on a small biopsy. Also, as they grow, pressure on the heart or lungs may cause symptoms such as breathing problems or chest pain. In large benign thymoma or with thymic carcinoma, chemotherapy and radiotherapy may be given after the surgery to control the disease.  In cases of advanced thymic carcinoma where surgery may be difficult to remove all the disease, chemotherapy and radiotherapy may be given first, to shrink the tumour and surgery performed afterwards.

Surgery – Thymectomy

When the thymus is small and for benign tumours that are not attached to the heart or vessels, surgery can be performed via minimal access or thoracoscopic / VATS techniques. The recovery is normally quick, with the usual in-patient stay of 2-3 days and back to work at two weeks. However, where the tumour is larger or to ensure the malignant tumour is removed as completely as possible, an open operation by sternotomy or a thoracotomy may be required. The in-hospital stay is usually around 5 days and it will be 4-6 weeks before most activities such as work or driving can be restarted.
King’s College Hospital, Dubai Hills, is one of the few centres in the UAE with surgeons who have wide experience of performing minimal access (thoracoscopic) thymic surgery.