Mediastinal malignant lymphoma difficult to diagnose: a patient report.

We report a 58-year-old man who suffered from shortness of breath on exertion with wheezing. A chest enhanced computed tomography (CT) scan showed an irregular tumor in the middle mediastinum involving the right main pulmonary artery, vena cava superior and right main bronchus. Transbronchial lung biopsy and endobronchial ultrasound-guided transbronchial needle aspiration yielded no evidence for a pathological diagnosis of malignancy. We employed mediastinoscopy, which led to a diagnosis of lymphoid reactive change. 18F-fluorodeoxyglucose-positron emission tomography (FDG-PET) scan revealed a high FDG uptake in the tumor lesion. Because the CT scan and FDG-PET findings led to a marked suspicion of malignancy, we decided to attempt biopsy by a video-assisted thoracoscopic surgery (VATS) approach. Flow cytometry showed a monoclonal pattern, and the final diagnosis was mediastinal follicular lymphoma both pathologically and immunohistologically. The patient achieved a complete remission by following chemotherapy. Low-grade malignancy type of lymphoma such as follicular lymphoma that generally contains small-cell components often presents a diagnostic challenge and the VATS approach was effective for the diagnosis of such type of mediastinal lymphoma.