Thymoma: the silent tumor hidden behind the sternum

In the vast and complex landscape of thoracic tumors, there exists a neoplasm as rare as it is intriguing, due to its silent nature and its connection with an often-overlooked organ: the thymus. «Thymoma is a rare tumor that arises from the thymus, a small gland located in the upper part of the thorax behind the sternum», says Francesco Guerrera, thoracic surgeon at Molinette Hospital in Turin, who has been treating thoracic tumors for years, from lung cancer and pleural mesothelioma to rarer neoplasms such as thymoma.

The doctor continues: «The thymus is an organ that plays an important role in the development of the immune system, especially in children and young people. With age, this organ naturally tends to shrink, but in some cases it can give rise to tumors, including thymomas».

Thymoma can remain completely asymptomatic for a long time, and it is precisely this that often makes it an incidental finding, discovered during a thorax X-ray or CT scan performed for unrelated reasons. Moreover, the silent nature of thymoma is what makes it particularly insidious. In fact, in many cases, patients reach a diagnosis without having experienced any symptoms.
Only when the mass grows and compresses nearby structures can it cause thorax pain, persistent cough, or breathing difficulties. «Sometimes, thymoma can be associated with immune system disorders, such as Myasthenia Gravis, an autoimmune neuromuscular disease», Guerrera notes.

Unknown causes and diagnosis

Although it is more common in adulthood, thymoma is not linked to smoking or other lifestyle factors. Its causes remain largely unknown, and no environmental or genetic risk factors have been clearly identified. «Thymoma is a tumor that mainly affects adults between the ages of forty and seventy, with no marked difference between men and women», the doctor continues.

Suspicion usually arises from an imaging study of the thorax that reveals a mass in the anterior mediastinum.

«That is, in the upper thorax behind the sternum, located between the lungs. Typically, further investigations are carried out, such as a contrast-enhanced CT scan, possibly a biopsy, and a global assessment of the patient’s health – says Guerrera -. In more complex cases, ancillary tests may be required, such as MRI, PET, or echocardiography. In some cases, however, the definitive diagnosis is only made after surgery. The timeframe may vary, but generally the aim is to reach a conclusion within a few weeks».

Minimally invasive surgery and a multidisciplinary approach to thymoma

The main treatment is often surgery. «When the thymoma is operable, the procedure consists in its complete removal, and today we can do this using minimally invasive or robotic techniques that combine great precision with a significant reduction in surgical trauma – Guerrera comments -. In more advanced cases, where the tumor extends to other structures, it may be necessary to combine surgery with radiotherapy or chemotherapy, either before, after, or even both before and after the operation».

In the case of rare tumors, the therapeutic pathway is personalised and discussed within a multidisciplinary team. Depending on clinical needs, thoracic surgeons, oncologists, radiotherapists or radiation oncologists may be involved, along with other specialists such as radiologists, nuclear medicine physicians, or pulmonologists.

Thymoma is a tumor that, by its nature, tends to grow slowly in most cases. Consequently, if it is diagnosed early and completely removed at an initial stage, the chances of avoiding recurrence can be very high.

«As with every oncological disease, time is a crucial factor. The sooner a thymoma is detected, the better the chances of effective treatment», Guerrera concludes.