mediastinal mass

A mediastinal mass is an abnormal lump growing in the central compartment of the chest. Because that corridor is so crowded with vital organs, even a modest growth can make trouble by pushing on its neighbors — and where in the mediastinum it sits gives the strongest first clue to what it is.

Location guides the differential diagnosis. Masses toward the front commonly include thymus tumors (thymoma), lymphoma, germ-cell tumors and a substernal thyroid — the classic teaching aid of thymoma, teratoma, thyroid and 'terrible' lymphoma. The middle compartment tends toward enlarged lymph nodes, cysts and vascular causes, while the back often holds nerve-derived tumors. Many masses are silent and found incidentally; others cause cough, chest pain, or symptoms from pressure on the airway, esophagus or the large veins.

Working one up means characterizing it with imaging — usually CT, sometimes MRI or PET — and frequently obtaining tissue, since treatment differs enormously between, say, a benign cyst, a lymphoma and a thymoma. Biopsy may be done with a needle, through a bronchoscope using ultrasound, or surgically, with the route chosen to reach the lesion safely and get a confident diagnosis.