April, 1917] Tumors in Dogs 181 



Fig. 4 is introduced from a spindle cell carcinoma occurring 

 in the thyroid gland of a horse. The elongated epithelial tumor 

 cells may be seen arranged in a kind of bundle formation so 

 that the resemblance to neoplastic connective tissue cells (a 

 sarcoma) is even more striking than in the canine specimens. 

 Areas can be found in which the carcinomatous cells appear to 

 be distinct from the sarcomatoid groups. If these strands of 

 spindle cells are followed, it is observed that the cells change 

 to spherical shape and then are arranged into more or less 

 definite tubules. So that, while these specimens, upon casual 

 examination appear to be adeno-sarcomas or sarco-carcinomas, 

 a more careful study makes it appear that there is only one 

 type of tumor cells present and that these are epithelial cells. 

 This is in agreement with the observation of Ewing ('16) that 

 epithelial tumors may from their inception appear like spindle 

 cell sarcomas as, in the spindle cell carcinoma of the thyroid. 

 It is becoming more and more apparent that many so-called 

 sarcomas of the organs are in reality spindle cell carcinomas." 

 A more decided lack of differentiation of the tumor cells in 

 both specimens and the presence of metastasis in the one 

 instance indicate that this is a more malignant type of cancer as 

 compared to those in Group 1. 



Group 3. Ten specimens are placed in this group w^hich 

 appear much the same as carcinoma seen in other organs and 

 as seen most frequently in the thyroid gland of man. A whole 

 lobe and often both lobes are involved in the growth. The 

 tumor substance is of a pearly white color except where it has 

 undergone necrosis or a hemorrhage has occurred into it. The 

 tumor is subdivided into smaller spheroid masses, measuring 

 1 to 5 cm. in diameter, by strands of fibrous tissue. The gross 

 sectional appearance and the extent of the involvement can be 

 seen in Fig. 9. 



The tumor cells vary in size, shape and arrangement. Six 

 of these specimens show a tendency to form tubules. The cells 

 are cuboidal for the most part. In certain tubules, however, 

 they are high columnar. An occasional tubule is well formed 

 and contains colloid. 



All stages of transition from the more nearly normal tubules 

 to strands of typical tumor cells, and further still, to masses of 

 cells with no definite arrangement, supported in a delicate 



