336 



TUMORS. 



Epithelial tumors always contain, in addition to the more or less 

 characteristic cellular elements, a connective-tissue stroma which gives 

 them support and carries the vessels (Fig. 182). This stroma may be 

 sparse or abundant, may contain few or many cells, is sometimes ar- 

 ranged in irregular fascicles or bands, and very frequently forms the 

 walls of well-defined, variously shaped spaces or cavities called alveoli, 

 in which the epithelial cells lie. The epithelial cells, in most cases, lie 

 along the walls of the alveoli without an intimate connection with them. 

 They are, moreover, packed together without more intercellular substance 

 than the usual cementing material common to epithelial cell masses. In 



FIG. 183. ADENOMA OF THE MAMMA. 



this lack of fibrillar intercellular substance within the alveoli, and in the 

 loose relationship between the cells and the alveolar walls, lie in many 

 cases the chief morphological distinctions between certain carcinomata 

 and alveolar sarcomata. 



In certain of the epithelial tumors there is a reproduction of typical 

 gland tissue of various kinds, depending upon the seat and conditions of 

 growth of the tumor. Such tumors are called adenomata (Fig. 183). A 

 simple hypertrophy of a gland, or an increase in its size by excessive 

 growth of its interstitial tissue, does not constitute an adenoma. There 

 must be an actual new formation of more or less typical gland tissue. 

 This is not always or frequently of exactly the same character as the 

 gland tissue in which it originates, and always exhibits a certain lack of 

 conformity to the type in structure and mode of growth. The alveoli 

 and ducts usually have a lumen and sometimes a membrana propria, but 

 the cells may differ in shape from one another and from those of the 

 gland from which they spring. 



Epithelial tumors in which there is no close conformity to a glandu- 

 lar type, but an independent and atypical growth of epithelial cells in 

 the meshes of an old or new-formed connective-tissue stroma, are called 

 carcinomata (Fig. 182). 



It will readily be seen that there must be a border region between 



