TUMORS. 



503 



The clinical diagnosis, in many instances, is possible when 

 there is a rapid growth and local multiplication ; often, however, 

 the tumor has all the appearances of a benign growth, while 

 microscopic examination reveals its malignant nature. An error 

 in diagnosis may occur owing to the circumstance that myeloma, 

 upon approaching the surface, as a rule does not cause ulcera- 

 tion of the skin, neither are the neighboring lymphatics enlarged 

 or painful. Sometimes myeloma appears in great numbers, almost 

 simultaneously in different parts of the body, and tumors, which 

 already have reached a certain size, may gradually disappear and 

 return again. Local recurrence after extirpation is a common 



FIG. 202. ALVEOLAR MYELOMA, FROM THE MESENTERY 

 OF A YOUNG MAN. 



F, frame composed of a delicate fibrous connective tissue, carrying blood-vessels, inclos- 

 ing alveoli ; the latter contain C, the spindle-, pear-, or irregularly shaped plastids. Mag- 

 nified 600 diameters. 



feature ; and so is multiplication, especially in the lungs, which 

 are sometimes found crowded with whitish, slightly vascularized, 

 tumors, the size of a poppy -seed, a hazel-nut, or a walnut. 

 The same may be found in the pleura and the peritoneum. Mel- 

 anotic myeloma selects the subcutaneous tissue, mostly of the 



