TUMORS. 



305 



Spindle-Cell Sarcoma.— Tumurs of this variety are composed 

 of spindle-shaped cells. They are more firm and dense than the 

 round-cell sarcomata. These tumors are not rare, occurring 

 most frequently in connection with the skin or sul)cutaneous 

 tissue. Some of the resistant and incurable cases of fistulous 

 withers are spindle-celled sarcomata. A collar boil that did not 

 respond to treatment was found to be a spindle-cell sarcoma. 

 These tumors are common in the eyelids of horses and mules 

 and are sometimes quite resistant to surgical interference. The 



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Fig. 160. — Section from spindle cell Sarcoma of a mule's eyelid. 



cells vary from short, thick fusiform cells to elongated fibre-like 

 cells. Spindle cells are more matured than the cells of round- 

 cell sarcoma. Round cells liave no tendency to becinne spindle 

 cells, neither do spindle cells become either round cells or ma- 

 tured connective tissue cells. The cells in spindle-cell sarcomata 

 have no definite arrangement but extend in all directions. In 

 microscopic section some cells are cut transversely, others ob- 

 liquely, and still others longitudinally. Hence we find the 

 nucleus is centrally located, is usually spherical or oval in shape, 

 and is not as large in proportion to the size of the cell as that 

 of the round cells. Some have suggested a classification of this 



