392 HISTOLOGY OF THE MORBID PROCESSES. 



nosis in a case of carcinoma or epithelioma, that metastasis may 

 take place while the primary growth is still of very small size, 

 even before attention has been called to the existence of a tumor. 

 An examination of the peripheral portion of the growth will often 

 throw considerable light upon the probability that this has occurred, 

 by revealing an extension of epithelial cells into the lymphatics of 

 the surrounding tissues. Cases of speedy recurrence of such a 

 growth after operation are really cases in which tissues that have 

 thus been infiltrated have not been completely removed. 



Much has been written within late years advocating the theory 

 of a parasitic causation of carcinomata and epitheliomata. The 

 appearances which have led to this belief are probably due to 

 degenerative or morbid processes within the epithelial cells of the 

 tumor, and not to the presence of parasites ; but further study of 

 this subject may show that parasites have the power of causing 

 rejuvenescence of cells and an emancipation from the ordinary 

 restraints that regulate their development. 



4. Cystoma. Attention has been called to the cystic adenomata 

 of the mamma. Similar cysts may occur in other regions through 

 dilatation of cavities normally present in the tissues by some fluid, 

 usually of a serous character. It is best to exclude cystic growths 

 in which the cystic character is evidently a secondary feature of the 

 tumor, or where a cyst arises from the retention of a secretion or is 

 due to the accumulation of a fluid in a normal cavity, from the 

 group of tumors that are essentially cystic. Thus, for example, 

 simple hydrops folliculorum of the ovary should not be classed with 

 the cystic tumors of that organ. 



The ovary is the favorite site for cystic tumors of new formation, 

 which may contain only a single cavity (unilocular) or several cav- 

 ities (multilocular). Histologically, they may be grouped in three 

 divisions : 1, simple, in which the walls of the cyst are smooth and 

 covered with epithelium ; 2, papillary, in which there are ingrowths 

 from the walls of the cysts into their cavities, either simple or branch- 

 ing (Fig. 361) ; and, 3, dermoid, which contain structures simulating 

 the normal skin : hair, imperfectly developed teeth, or other highly 

 differentiated tissues, such as bone, etc. In the first two forms the 

 fluid in the cystic cavities may be serous, mucoid, or colloid ; fre- 

 quently it is different in the various cavities of the tumor. In der- 

 moid cysts there is often a greasy substance, similar to the sebum 

 of the skin, derived from sebaceous glands in the cutaneous struct- 



