Purpose. Due to the primary mediastinal seminoma rarity and the absence of cases with it complete surgical removal description in world literature, according to our data, we would like to bring to your attention the following observation of the patient.

Materials and methods. A 45 years old patient with a mediastinal mass. In one of the oncologic clinics, after transsternal puncture, tuberculosis was morphologically diagnosed. On admission to our clinic, a giant tumor of the anterior mediastinum was visualized with multislice computed tomography (MSCT). It was located from the subclavian vein to the level of VII ribs. The diagnosis on admission was intrathoracic lymph nodes tuberculosis, but it raised doubts. Due to the presence of vena cava syndrome, it was decided to conduct a medical diagnostic surgery as a matter of urgency. From the right lateral thoracotomy giant formation weighing 1500gwasremoved. It compressed heart, mediastinum vessels and trachea.

Results. On the basis of a combination of histological and immunohistochemical signs, a typical seminoma was diagnosed. Postoperatively, the patient received 3 courses of chemotherapy from 9 prescribed (refusal of treatment). 9 years after surgery, the patient is healthy, working, without recurrence. Radiological diagnostic methods application does not allow definitively diagnosing the mediastinum seminoma, since in this case it is impossible to differentiate it from tumors of a different etiology. A histomorphological study with transthoracic biopsy is considered to be the “goldstandard” of diagnosis, however, even with this method, diagnostic errors are possible. In our case, we performed surgery without re-biopsy due to the rapid deterioration of the patient's condition.

Conclusion. In our opinion, the right lateral access is the most successful for removing giant mediastinal tumors, from which manipulations in the left pleural cavity through the anterior mediastinum are also possible.