SQUA MO US-CELLED CANCER. 303 



stage of development, its general structure is distinctly gland- 

 ular, consisting of tubular or rounded gland-like spaces or 

 alveoli lined with cylindrical epithelium. It is distinguished 

 from simple adenoma, however, which it greatly resembles, 

 by the irregular arrangement of the marginal epithelium, by 

 the masses of epithelial cells which often completely fill the 

 lumen of the alveoli, especially in the older parts of the 



FIG. 132. 



Medullary carcinoma of the mammary gland (Hansemann). The stroma of the 

 tumor is here reduced to a minimal amount of areolar tissue containing the 

 vascular supply of the growth. 



tumor, and by epithelial cells which have broken through the 

 basement-membrane and infiltrated the connective-tissue 

 stroma between the alveoli. 



Squamous-celled cancer, or epithelioma, arises from surfaces 

 covered by stratified squamous epithelium, as from the skin, 

 oesophagus, larynx, lips, etc. The proliferating epithelial 

 cells show the characteristic tendency noted in all cancers to 

 extend beyond normal limits and infiltrate adjacent tissues. 

 The tumor is found to be composed of masses of flat epithelial 

 cells grouped in conical or irregularly shaped processes or 

 columns of variable length and breadth, simple or branching, 

 and separated from one another by a scanty connective-tissue 

 stroma. At many places in the deeper parts of the tumor, as 



