TUMORS. 



325 



masses or as ulcerated surfaces and are rarely encapsulated. 

 Iheir consistency varies with the amount of connective tissue 

 stroma present. Their color is usually white or <?ray, althouo-h it 

 may be quite variable as a result of defeneration or necr^osis. 

 The quantity of blood depends upon the vascularity of the tissue 

 invaded. 



Microscopic sections of epitheliomata are usually very similar 

 to carcinomatous sections, indeed, it is sometimes impossible to 

 differentiate them from carcinomata. In the beginning of the 

 tumor formation, if sections are made perpendicular to the sur- 



■ MS 









,<S"i:«?; 



:.ff^y 









Pig. 17S. — Section or a peail i-.-ll Enitlielninia m1 ilir Sithnttiiiii "i li 1 I -\i.Lir-i>ia 

 dog, showing" pearl cells and coJunDis '>!' i]>itlii lial ceils. 



face, the ingrowing epitlielium will ])e ol)ser\-cd as columns of 

 cells. These cell columns extend int("i the areolar h-mph spaces 

 and -are then distributed the same as in carcinomata, the pre- 

 existing tissue stroma becoming the stroma of the tumor. The 

 presence of the epithelial cells or their katabolic products some- 

 times produces a chronic inflammation of the stroma. The pres- 

 sure produced from the thickened stroma upon the columns of 

 epithelial cells may result in the formation of "pearls." Epithe- 

 liomata containing the "pearls" are designated pearl-cell epithe- 

 liomata. 



