TUMORS OF THE STOMACH. 377 



When there is pyloric obstruction its capacity may be greatly 

 increased (Fig. 168); or much diminished if such a con- 

 dition exists at the cardia, or if there is a diffuse carcinoma- 

 tous infiltration of the walls of the organ (Fig. 169). If 

 the pylorus is not supported by adhesions, it may sink to the 

 pelvis. 



Metastases occur in one-half the cases ; the liver is in- 

 volved in over one-third of them. The neighboring lym- 

 phatic glands, especially those behind the lesser curvature of 

 the stomach, become converted into large cancerous nodules, 

 and the peritoneum is often involved by direct extension of 

 the tumor-formation. 



Histologically several varieties of the neoplasm are recog- 

 nized : 



Scirrhus is the most common, constituting about 75 per cent, 

 of the cases. There may be a ring-like contraction at the 

 pylorus, or a diffuse infiltration of the walls of the stomach 

 without any nodular prominences, which condition might be 

 confounded with a hyperplastic interstitial gastritis. Occa- 

 sionally small, flat nodules occur on the serous surface over 

 the region of the tumor. If the mucous membrane ulcerates, 

 which is rare, it is only superficial. Scirrhus is almost in- 

 variably situated at the pylorus. 



Encephaloid grows very rapidly, and forms large, soft, gray- 

 ish-white, irregular, papillomatous masses, which project into 

 the cavity of the stomach. It is so prone to undergo necrosis 

 that it generally presents at the autopsy as a bowl-shaped, 

 ulcerating depression, with irregular, ragged walls of varying 

 height and thickness, formed by the surrounding tumor-mass. 

 Perforation may result from extensive ulceration. 



Adeno-carcinoma in general appearance resembles encepha- 

 loid, and tends to undergo extensive ulceration in a similar 

 manner. 



Squamous-celled cancer affects the region of the cardia, tak- 

 ing its origin from the flat cells of the resophagus. 



Colloid carcinomata have a transparent jelly-like appear- 

 ance, due to the degenerative change they have undergone. 

 This degeneration may affect any form of cancer, but more 

 especially adeno-carcinoma. 



