TUMORS. 



311 



development, until they form very large, irregular, loose-textured tumors, 

 which often finally ulcerate. Such forms are seen in the mammary 

 gland, where they are sometimes mistaken for carcinomata. They are 

 called Intracanalicular Fibromata (see Fig. 463, page 707). 



It is often difficult to distinguish between genuine fibromata and in- 

 flammatory or other connective-tissue hyperplasias, such as elephantiasis ; 

 and perhaps the fuller knowledge of the future will show that the dis- 

 tinctions are not as definite as our classifications indicate. 



MYXOMA. 



MuOjia7tissue is essentially an embryonic tissue, for in the normal 

 adult it is present only in a very imperfect jiud atypical form in the 



FIG. 149. MYXOMA OF THE LARYNX. 

 Showing the diffuse staining of the mucin-containing stroma with haematoxylin. 



vitreous of the eye, and perhaps exceptionally in small amount about 

 the heart, kidneys, and medulla of bone. 



The myxomata are thus essentially embryonic-tissue tumors. These 

 tumors consist, in their most typical forms, of a homogeneous or finely 

 fibrillated, soft, gelatinous basement substance, in which are embedded a 

 variable number of spheroidal, fusiform, branching, and often anas- 

 tomosing cells (Fig. 149). They may contain few or many blood-vessels 

 and sometimes nerves. By the addition of acetic acid, muciu may be 

 precipitated from the basement substance. In sections it is usually 

 stained with hsematoxyliu. The very soft forms which contain compara- 

 tively few cells and much translucent basement substance are called 

 Myxoma gelatinosum or M. molle. The presence of many cells renders 

 them more consistent and gives them a whiter and more opaque appear- 

 ance ; such forms are called M. medullare. 



Pure myxomata are not commojjj,. The myxomata are very apt to be 

 combined with fibrillar connective tissue as fibro-myxoma ; or with fat 



