Primary seminoma arising in the posterior mediastinum: a diagnostic challenge.

Primary mediastinal germ cell tumors are a rare finding, and one third of them are seminomas. Seminomas are found in the anterior mediastinum, whereas they are extremely rare within the posterior compartment. Most clinicians would not consider a primary seminoma in the differential diagnosis of a posterior mediastinal mass, as only two cases have been reported in literature. Here we present the case of a 57-year-old male with a primary seminoma arising in the left posterior mediastinum. He was asymptomatic and the mass was an incidental finding. Positron emission tomography (PET) revealed a small area with an avid tracer uptake. Transthoracic needle aspiration led to a non-diagnostic result. Due to the strong suspect of malignancy, a surgical excision was chosen to obtain a diagnosis. He underwent complete excision, and pathology report demonstrated a mediastinal seminoma. Subsequent further staging did not reveal any other location of the disease. Given the complete excision of the primary tumor, active surveillance was the treatment of choice. The patient is free of disease 48 months after diagnosis.