“…It is evident from our results and previous investigations that neither the clinical picture nor the radiographic findings can confirm whether a substernal tumour is benign or malignant (Key, 1954;Videbaek and Thomsen, 1959;Daniel, Diveley, Edwards, and Chamberlain, 1960;Kalter, Liebermann, and Pauzner, 1964;Sawyers and Foster, 1968;Shields, 1969;Fontanelle et al, 1971). Any patient with a tumour of the thymic region must therefore be subjected to operation without delay.…”