ACUTE PROMYELOCYTIC LEUKEMIA - MORPHOLOGICAL AND CLINICAL-FEATURES

Background and Methods. Acute promyelocytic leukemia (APL) is not a mo rphologically homogeneous entity: to verify whether there is any relat ionship between this heterogeneity and other biological and clinical a spects, we studied 43 cases of APL with morphological, cytochemical, c ytogenetic and immunological methods. Results. Three morphological cat egories were present: a classic hypergranular type (30 cases), a micro granular type (6 cases) and a form with basophilic granules (M3b) that stained metachromatically with toluidine blue (7 cases). In all these groups there were cases with cytochemical features of both myeloid an d monocytic type (alpha-naphthyl-acetate esterase positive). No immuno logical and cytogenetic differences were observed; the morphological v ariant with basophilic granules was more frequent in females; age dist ribution was not related to the morphological subtype; organomegaly wa s extremely rare in M3b. A low white blood cell count was constant in M3b, whereas no differences were observed in hemoglobin and platelet v alues. Severity of bleeding was worst in the group with toluidine blue metachromasia; this and the microgranular type had poor prognosis. Co nclusions. Our study confirms the importance of identifying different cytologic categories in APL. In particular we focused our attention on a new variant with basophilic granules.