Most cases of ALL also do not have identifiable immunologic surface markers. This slide shows sheep red blood cells forming rosettes around lymphoblasts, thus identifying them as T cells. Other immunologic techniques have been used to show that some cases of ALL are proliferations of bursal-derived lymphoblasts (B cells). However, about three fourths of all cases of ALL cannot be identified as either T- or B-lymphocyte cells, and consequently these blasts are called "null" cells. The immunologic and morphologic subclasses of ALL do not necessarily coincide; no morphologic feature is consistently associated with any immunologic marker (or lack of marker, for that matter).
Course Section: 07. Lymphocytic Leukemia: Acute and Chronic
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