272 TJie Lymphocyte and Lymphocytic Tissue 



the chromatin pieces become smaller and finer, and the resulting cell at this 

 stage manifests its blood-cell-forming propensities. The poorly delimited, 

 irregularly outlined nucleoli usually remain small in the nonleukemic 

 transformations (Figs. 19-7, 19-8) but may become unduly prominent (Fig. 

 19-9) when the heterologous change is leukemic in nature. The hemato- 

 poietic reticulum cell has been descriptively labeled "hemohistiocyte" 

 by Ferrata. 23 



Fig. 19-9. Hematopoietic reticulum cells that were also leukemic. 

 Bone marrow of so-called acute monocytic leukemia. Leishman stain. 

 (X 1100) 



LEUKEMIC BLOOD-FORMING RETICULUM CELLS 



Ewald 20 first described a leukemic process centered at the hematopoietic 

 RE cell stage, and Downey 1 " followed with excellent descriptions of the 

 blood-forming RE cell in leukemic and nonleukemic environments. If the 

 leukemic process consists of an overgrowth of leukemic hematopoietic RE 

 cells without further differentiation toward any or the blood cell lines, then 

 Ewald's and Downey's descriptive term "leukemic reticuloendotheliosis" ap- 

 plies, although the term "reticulum cell leukemia" is equally as descriptive 

 and is more informative of the true nature of the condition than Aschoff's 

 suggestion 1 of "histiocytic leukemia." The Italian designation of hemo- 

 histioblastic leukemia is a good descriptive term emphasizing that the leu- 

 kemic process is centered between the tissue cell and the stem cells of the 

 blood. Less fortunate is the term "monocytic leukemia" which has become 



