CARCINOMA. 301 



Adenoma of the liver probably arises from the bile-ducts, as 

 its epithelial elements differ "in structure from the hepatic 

 cells. 



Carcinoma. 



A carcinoma, or cancer, is the malignant variety of the epi- 

 thelial-tissue group of tumors. The arrangement of the rap- 

 idly multiplying epithelial cells, of which the tumor is mainly 

 composed, with reference to the connective-tissue stroma is 

 atypical, peculiar to carcinoma not seen in any other tissue 

 in the body, though often suggestive of glandular structures. 

 The cells originate from surface or glandular epithelium ; 

 breaking through normal anatomical boundaries, they infiltrate 

 the surrounding connective tissue, which in its turn thus pro- 

 liferates, and thus their mutual interpenetration gives rise to 

 the microscopical structure which is always diagnostic of carci- 

 nomaepithelial cells in an alveolar stroma. The cells are very 

 apt to retain to a certain extent the characteristics of those 

 from which they originated : if from one of the glands of the 

 stomach, the new-formed cells also are cylindrical, and often 

 seem to attempt to reproduce glandular tissue i. e., there are 

 variously shaped spaces more or less regularly lined by epi- 

 thelium. If from the epidermis, the newly-formed squamous 

 cells may show the same tendency to cornification. 



The amount of the stroma varies ; if considerable, the 

 growth is hard scirrhous; if scanty, it is soft and brain-like 

 encephaloid; further, it is often quite cellular from the 

 presence of infiltrating leukocytes or newly-formed connective- 

 tissue cells. Metastasis occurs through the lymphatics, while 

 in sarcoma it occurs through the bloodvessels. The secon- 

 dary growths have the same general structure as the primary. 



Carcinoma occurs most frequently between the ages of 

 forty-five and sixty-five, and is found most frequently in the 

 uterus, gastro-intestinal tract, skin, mammary gland, ovary, 

 and occasionally in the liver, kidney, thyroid, and prostate 

 gland. It is quite liable to retrograde changes fatty and 

 colloid degeneration, necrosis, and ulceration. 



Several varieties are described according to the character 

 of the epithelial elements squamous, cylindrj^*. 

 which compose the tumor : 



LI BR ARY 



