Subclassification in acute lymphoblastic leukaemia: acid phosphatase reaction and immunological markers in relation to clinical features. A comparative study of 44 patients.

A prospective, comparative study of cytochemical and immunological markers and clinical features was undertaken in 44 patients with ALL (children and adults). 12 patients (27%) had T-ALL, 1 patient (2%) B-ALL and 31 patients (71%) (non-T, non-B)-All. E-rosetting lymphoblasts ranged from 35 to 96% (median: 61), highest when AET-treated SRBC were used as indicator cells. All 12 E-rosette positive cases were strongly acid phosphatase (AcP)-positive, showing a homogeneous pattern of distinct granular AcP-activity in more than 85% of the lymphoblasts (median: 96%) significantly different from the median of 26% granulated blasts found in (non-T, non-B)-ALL cases. Counting blasts with granular AcP-activity proved to be both easier than using a scoring system for the AcP-reaction and more efficient in terms of discriminating ability between the subgroups. Significant clinical and haematological features characterizing the T- and AcP-positive cases included: (1) Predominance of young adult men, (2) presence of a mediastinal mass, (3) involvement of skin and serous membranes, (4) only slightly affected haemoglobin concentration at presentation, (5) difficulty in obtaining complete remission, (6) shorter duration of first complete remission and (7) shorter survival rate. It is confirmed that AcP-staining of lymphoblasts is an easy, reproducible and inexpensive method for identifying the T-cell variety of ALL.