182 The Ohio Journal of Science [Vol. XVII, No. 6, 



stroma. These masses may be separated by bands of dense 

 connective tissue and thus given an alveolar arrangement. It 

 is in these masses, that the greatest variation is seen, both in 

 the same tumor and in different tumors. In seven of the spec- 

 imens, the cuboidal cell is the predominating one. Occasion- 

 ally a mass of large spherical cells with clear, lightly staining 

 cell bodies and small dark nuclei are encountered. In three of 

 the specimens, this same type of cell predominates so that these 

 specimens appear to be of the medullary type of carcinoma. 

 In many instances the blood vessels are filled with the growth. 

 In six of the cases, definite metastatic nodules are present in 

 the lungs (Fig. 10). Unfortunately, a search through the 

 marrow of the bones of each animal could not be made. Since 

 this is a frequent site for the secondary growth of thyroid 

 tumors, no doubt, instances of metastasis might have been 

 found. In the lungs presenting metastatic nodules, many of 

 the vessels are filled with tumor cells. One of these specimens 

 illustrates defense against the tumor cell which has found its 

 way into the circulatory system. That is, there is a prolifera- 

 tion of endothelium and an ingrowth of connective tissue in 

 and around the embolic mass of tumor cells to such an extent 

 that the tumor cells have been completely crowded out. (Figs. 

 5, 6, 7, S). These tumors are distinctly malignant. The 

 number of metastases indicates this as well as the histological 

 picture. 



Group 4. Another form of thyroid malignancy is illustrated 

 by a single specimen in our series. The greater part of this 

 tumor was not brought to the laboratory, but was used by 

 Drs. Scott and Dodd in an unsuccessful experiment in trans- 

 plantation. Our description of the specimen, therefore, rests 

 on the findings in four blocks of tissue embedded in celloidin. 

 The growth is composed of whitish nodules and cystic cavities 

 filled with the tumor growth. 



Microscopical examination reveals dilated gland lumina into 

 which extend many papillary growths of connective tissue cov- 

 ered with epithelial cells of columnar type. (Fig. 17). The 

 tendency to develop into a papuliferous growth is seen even in 

 the more solid nodules of the tumor. The papillary cyst- 

 adenoma is encountered occasionally in the human and is 

 usually placed in a class between benign and malignant growths. 



