Structure of Lymphocytic Series of Cells in Relation to Disease 275 



lymphomas of the lymphoblastic cell type (Fig. 19-12 and Table 19-1), it is 

 rare indeed if hematopoietic RE cells of a malignant nature are not readily 

 discernible in the imprints of affected nodes, spleen, or other organs in- 

 volved. 



LYMPHOBLASTS, NONLEUKEMIC 



In reactive heterologous lymphocytopoiesis studied in imprinted material 

 stained like blood smears, the resultant of the transformation of the inactive 

 reticulum cell to a blood-forming reticulum cell is a nonleukemic lympho- 

 blast. The term "nonleukemic lymphoblast" is used here because the lym- 

 phoblast described and depicted in most textbooks of hematology is a 

 leukemic lymphoblast as found in the blood of the acute lymphocytic 

 leukemias. The nonleukemic lymphoblast (left immature cell of Fig. 19-1 1) 

 of the lymphocyte-forming tissues at first shares in the abundant cytoplasm of 

 its precursors, but it gradually presents only a moderate band of varying 

 shades of pale to dark-blue color. Azurophilic granules are usually absent. 

 The nuclear pattern is surprisingly similar to that of the blood-forming 

 reticular cell nucleus with an irregular network of light-violet stipples or 

 particles of chromatin sharply set off from colorless interstices, themselves 

 irregular, angular, and unequal in size. The nucleoli, which are always 

 present, may be masked by the chromatin or as many as five nucleoli may 

 be found, usually however, one or two pale-blue, round nucleoli are present. 

 The nuclear membrane is thin, thinner in fact than the nuclear membranes 

 of the cells preceding or succeeding it in lymphocytopoiesis (Table 19-1). By 

 reason of its larger size and reticular nuclear pattern, the lymphoblast of 

 reactive lymphocytic tissues could be aptly designated a reticular lympho- 

 blast. 



LYMPHOBLASTS, LEUKEMIC AND 

 LYMPHOSARCOMATOUS 



In contrast to the cell described above, the leukemic lymphoblasts of 

 the acute lymphocytic leukemias are usually smaller and possess a nuclear 

 pattern indistinguishable by ordinary staining methods from the myelo- 

 blast or stem cell of the marrow elements. In this nuclear pattern, well 

 illustrated in any textbook of hematology, the chromatin is arranged in 

 fine strands or stipples with very regular but small interstices of colorless 

 parachromatin in which are embedded none or from one to five pale-blue, 

 round, or oval nucleoli. It is paradoxical that the leukemic lymphoblast 

 usually presents a neater, finer, more orderly chromatin arrangement than 

 its normal counterpart. 



At times the lymphoblasts of lymphocytic leukemia structurally resemble 



