2l8 



BIOLOGY OF THE LABORATORY MOUSE 



MYELOBLAST PROMYELOCYTE 



seen in the C57 black, C57 brown and C57 leaden stocks. There are occa- 

 sional reports in the literature on reticulum cell tumors and references to 

 cases in mice resembhng Hodgkin's disease (15, 26). J. Furth states that 

 most human neoplasms of the histiocytes have been described as reticulum 

 cell sarcoma or reticulosis, leukemic and aleukemic, but since the relation of 



histiocytes to reticulum fibers and to reticular 

 libroblast-like cells of blood forming organs is 

 obscure, this terminology is not desirable. He 

 suggests the use of the term histiocytoma or 

 monocytoma to cover these tumors in the blood 

 forming organs. 



Monocytoma. — Monocytes may form tumors 

 in the liver and spleen and infiltrate these and other 

 tissues. The liver becomes enormously enlarged 

 and mottled with minute irregular gray -white 

 masses of tumor cells, hemorrhagic areas and 

 yellowish-gray necrotic foci. The spleen and 

 lymph nodes may or may not be enlarged grossly. 

 Microscopically the spleen usually shows small 

 foci of tumor cells, hemorrhage and necrosis. 

 Occasionally the lungs show large or small areas 

 of hemorrhage with yellowish-gray foci of tumor 

 cells. Death usually results from internal 

 hemorrhage starting from the lesions in the 

 liver. 



There are leukemic and aleukemic forms of 

 this tumor. The cells are the large monocyte type 

 with oval, bean-shaped or irregularly lobed, 

 eccentric nuclei. Considerable non-granular 

 basophilic cytoplasm is present. Infiltration of 

 the liver is diffuse with frequent formation of small 

 tumor nodules. MaHgnant cells are seen within the blood vessels of the 

 liver, sometimes nearly occluding them. The spleen may show the same 

 type of tumor cells and blood vessel involvement. Lymph nodes may or 

 may not be involved. When involvement occurs, it is around the nodules. 

 Mitoses are somewhat numerous. The tumor cells have some phagocytic 

 ability. A condition exactly like Hodgkin's disease has not been found in 

 mice, but there are certain similarities between monocytoma and Hodgkin's 

 disease (15). 



POLYMORPHONUCLEAR 



LEUKOCYTE 

 Fig. 118. — Diagram 

 showing the development 

 of granular leucocytes 

 from the immature myelo- 

 blast to the fully formed 

 polymorphonuclear leuko- 

 cyte. Note the changes 

 in number and size of the 

 granules. {Redrawn from 

 Barnes and Sisman.) 



