TUMORS. 517 



Attention has recently been drawn to tumors which, in addition to well- 

 developed fibrous connective tissue, contain tracts or alveoli filled with finely 

 granular polyhedral nucleated plastids, resembling the endothelia of blood- 

 vessels. Tumors of this structure are termed endothelioma, and, as a matter 

 of course, are of a benign character. I have seen such formations in a 

 sebaceous adeno-fibroma of the scalp, in a lipo-fibroma of the skin of the face, 

 and in a tumor of the choroid the size of a sugar-pea. Endothelia are in their 

 structure identical with the medullary corpuscles, representing the stage of 

 indifference from which connective tissue and its derivations arise. In the 

 first instance, the endothelial tracts were like blood-vessels, but without per- 

 foration ; such tracts were also observed in the angioma of the skin of the 

 forehead of a child, illustrated in Fig. 209. In the second case, fat-globules 

 were found in the midst of the endothelia, and the conception was admissible 

 that fat originated from the endothelia, there representing an intermediate 

 stage. In the third case, alveoli were present, closely resembling cancer 

 nests. The differential diagnosis in such a case rests upon the regular arrange- 

 ment of the alveoli ; the lobular structure of the tumor ; the fully developed 

 fibrous connective-tissue frame, which is of a nearly uniform width and scantily 

 supplied with blood-vessels ; the fine granulation of the plastids and their pale, 

 finely granular nuclei. In such cases a positive differentiation between endo- 

 thelioma and epithelioma (cancer) seems difficult, if not impossible ; though the 

 clinical course of the benign endothelioma is altogether different from cancer. 



8. MYOMA. MUSCLE TUMOR. 



Tumors composed exclusively of striated muscles do not 

 occur ; striped muscle-fibers are constituents of tumors, appear- 

 ing occasionally in the testis and the ovary, which also contain 

 remnants of other tissues, such as cartilage, bone, teeth, and 

 hairs. These are the so-called " dermoid cysts" teratoid and 

 combination tumors. On the contrary, tumors composed of 

 smooth muscle-fibers are of frequent occurrence, always com- 

 bined, however, with fibrous connective tissue, constituting, 

 therefore, myo-fibroma or fibro-myoma. The organ which is the 

 most frequent site of tumors of this sort is the uterus, in middle 

 and advanced age, especially in the colored races. 



Myo-fibroma of the uterus appears either beneath the mucous 

 layer, in the middle of the wall, or at the periphery of the uterus 

 (submucous, intraparietal, and subserous myo-fibroma), and in 

 almost every instance more or less smooth muscle-fibers are 

 found mixed with the connective tissue. The latter tissue carries 

 the blood-vessels, which vary greatly in amount and sometimes 

 are so abundant as to justify a diagnosis of angio-myoma. 

 Fibrous tumors of the ovaries which I have examined exhibited 

 the same features. A subserous myo-fibroma of the uterus, under 

 the microscope, gave the appearances illustrated in Fig. 213. 



