Structure of Lymphocytic Series of Cells in Relation to Disease 277 



designate leukemic manifestations of malignant lymphomas as leukemia at 

 that stage when the marrow or blood shows more than token evidence of 

 involvement by the affected cell type. 



PROLYMPHOCYTES 



In homologous lymphocyte formation, lymphoblasts form additional lym- 

 phoblasts by mitosis or transform into immature lymphocytes intermediate 



Fig. 19-13. Three prolymphocytes [top center) surrounded by small 

 and medium-sized adult lymphocytes from a lymph node in infectious 

 mononucleosis. Note the small lymphocyte (center) in mitosis. 

 Leishman stain, (x 1100) 



in differentiation between lymphoblasts and mature lymphocytes (Table 

 19-1). These intermediates are termed "prolymphocytes" (Figs. 19-13, 19-14, 

 19-15). They may be the size of smaller lymphoblasts or may approach the 

 size of the largest of the mature lymphocytes. The cell body usually con- 

 sists of a very narrow band although occasionally it is larger. It possesses 

 any degree of basophilia from pale to dark blue. The most important dis- 

 tinguishing feature of the prolymphocyte is the finding in some nuclear 

 areas of a fine network of chromatin strands still distinct from the colorless 

 parachromatin interstices. Such immature areas blend imperceptibly with 

 nuclear areas, showing indistinct, coarse, clumped chromatin masses (Fig. 

 19-13). In other words, the chromatin pattern of the prolymphocyte is too 

 coarse to qualify as lymphoblastic and too fine and insufficiently massed to 

 be designated as mature. Occasionally a nucleolus is unmasked, but this 



