Mediastinal tumors: why, when, and how to biopsy?

The finding of a mediastinal mass often poses a diagnostic challenge for clinicians. A correct diagnosis on the nature of a mediastinal tumor is important prior to initiating any treatment. Therefore, good knowledge is needed on mediastinal anatomy and its different compartments as well as on the differential diagnosis of a wide variety of benign and malignant mediastinal lesions. A complete history of the symptoms and a full clinical examination together with imaging and laboratory tests can guide the clinician towards a final diagnosis at presentation. Pretreatment tissue biopsy of a mediastinal tumor is not always required in case the clinical diagnosis is highly probable based on the above findings and when the tumor looks well encapsulated and of non-invasive nature amenable to upfront complete surgical resection as judged by the thoracic surgeon. Tissue diagnosis is recommended for a clinically and radiographically for cancer suspected, locally advanced or unresectable mediastinal mass in order to confirm the diagnosis and to guide induction therapy or definitive systemic treatment. An ultrasound or computed tomography (CT)-guided core needle biopsy may result in sufficient tissue for definitive cytopathological diagnosis. Otherwise, a minimally invasive procedure by video-assisted thoracoscopy (VATS) or robot-assisted thoracoscopy (RATS) or occasionally an open surgical biopsy may be necessary to obtain more tissue for pathological examination and molecular testing. Depending on the location of the mediastinal mass in any of the mediastinal compartments, various surgical approaches can be chosen to biopsy. A frozen section is helpful to check the quality of the biopsy but is less effective for a precise diagnosis. The definitive pathological report needs to be awaited prior to initiating any treatment except in case of a life-threatening condition such as critical airway compression or superior vena cava syndrome.