Vascular invasion in bronchogenic carcinoma.

Most studies dealing with routes of spread of malignant tumours have been concerned primarily with dissemination by way of the lymphatic system. This emphasis has been placed correctly, for it is primarily in dealing with lymphatic spread that any surgical or radiotherapeutic approach toward control of cancer can be successful. It has also been recognized for a long time that malignant emboli may be disseminated by way of the blood stream. Efforts to study this route of spread have not been particularly rewarding, for any pathological examination must be limited to efforts at determining sites at which malignant cells may have reached the blood stream. Bronchogenic carcinoma has particular opportunities for widespread dissemination as a result of its ready access to the systemic circulation. Relatively few studies have been reported on the incidence of vascular invasion in surgically resected specimens of bronchogenic carcinoma, although many observers have noted the frequency with which tumours have been found within vessels in necropsy material (Adler, 1912; Barnard and Elliott, 1930; Fried, 1927; Grove and Kramer, 1926; Simons, 1937; Simpson, 1929; Weller, 1929). In 1951 Aylwin reported a number of observations on the frequency of venous involvement in surgically resected specimens of bronchogenic carcinoma. He studied 58 resected carcinomas, using as the criterion of vascular invasion the perrheation by malignant cells through all coats of the vessel at least as far as the intima. He found that 40% of the specimens showed malignant cells in contact with blood returning to the heart and that 80% of the patients whose specimens exhibited such microscopic findings died with widespread vascular deposits. He presented two cases in which massive malignant emboli resulted in death shortly after operation. Indirect evidence of venous and arterial invasion has been obtained by angiocardiography in the pre-operative evaluation of patients with bronchogenic carcinoma. Complete occlusion of a pulmonary artery as seen by angiocardiography has been reported by Wiklund (1951), and distortion of arterial patterns consistent with compression or invasion has been reported in various angiocardiographic studies (Dotter, Steinberg, and Holman, 1950; Keil, Voelker, and Schissel, 1950; Slesser, Britt, and Freer, 1954).