The formation of a clot in a vessel is not an infrequent event during the later stages of cancer of the stomach. As a rule the veins are more often affected than the arteries, especially those of the lower extremities. Thrombosis of the common iliac, femoral, or saphenous veins was observed in 4.5 per cent, of our cases. The condition appears to be due partly to the general debility that exists towards the end of life, and partly to the feeble action of the heart which ensues from the wasting and degeneration of its tissues. It is especially frequent in cases where the growth occupies the posterior wall of the stomach and is accompanied by intense anaemia (latent cancer). The basilic or cephalic veins of the arm, or the internal jugulars (Bouveret), are occasionally obstructed, while in rare instances most of the superficial veins of both the upper and lower extremities may be affected (Osier).
Thrombosis of the veins within the abdomen or thorax is usually due to their direct invasion by the growth. For this reason the portal trunk is most often affected, although sometimes its splenic or mesenteric tributaries are also involved. Portal thrombosis was noted in 3 per cent, of our cases, but it is probable that this figure underrates the frequency with which it takes place. Suppurative inflammation of the vein has been observed (Legg). Less frequently the inferior vena cava is invaded by a growth of the posterior surface of the stomach, or the hepatic veins by a secondary tumour of the liver ; while in one of our cases a metastasis in the superior mediastinum led to thrombosis of the right innominate vein and its tributaries.
Thrombosis of arteries is comparatively rare, and is usually preceded by atheroma, unless the vessel is directly involved by the neoplasm. It has been observed to take place in the middle cerebral (Merklen, Flint), posterior tibial, and left subclavian (Langlet), as well as in the splenic, hepatic, colic, mesenteric, and renal trunks. In one case we found simultaneous occlusion of the splenic, right renal, and right posterior tibial arteries. Ante-mortem clots in the cavities of the heart and in the pulmonary artery are usually present when death has been preceded by coma.