Distribution of malignant lymphoid cells.

About two-thirds of tumours of adult human lymphoid tissue originate from B cells; one-fifth derive from T cells; one-eighth are undefinable, using markers currently available; and fewer than one in a 100 are truely histiocytic, showing markers associated with monocytes (Lukes et al., 1978). B cells can be demonstrated in suitable tissue sections since they possess either surface or intracytoplasmic immunoglobulin. Evidence of monoclonality can be deduced from the pattern of immunoglobulin light chain staining (Warnke and Levy, 1978). Techniques are not yet available to enable similarly detailed studies to be performed on human T cells in tissue sections where structural relationships can be defined. The emphasis in this paper consequently is on B cell malignancies.