Immunostaining for nucleophosmin in bone marrow trephine biopsy specimens in acute myeloid leukemias.

Abstract

Objective: To evaluate the technicalfeasibility of nucleophosmin (NPM) staining and the problems of interpretations by pathologists in an academic regional hospital in Italy.

Study design: Acute myeloid leukemia (AML) is a heterogeneous clonal disorder of hematopoietic progenitor cells that presents genetic abnormalities in several genes, including NPM. Mutations of the NPM gene occur in 35% of patients with AML with normal karyotype, causing cytoplasmic rather than nuclear localization of the protein. Because the NPM antibody recently became commercially available, we immunostained a series of diagnosed AML samples. We performed NPM immunostaining in 48 AML cases. NPM immunostaining was correlated with phenotypic and cytogenetic data.

Results: Reactivity for NPM was exclusively nuclear in 31 cases (64.6%) and nuclear and cytoplasmic in 17 cases (35.4%). The distribution of NPM cytoplasmic staining was more frequently observed in cases with monocytic differentiation and with normal karyotype or with minor cytogenetic abnormalities (p < 0.05).

Conclusion: NPM immunostaining is a feasible test, without problems of interpretation for pathologists, when the sections are optimally prepared and can be considered predictive of peculiar phenotypic and karyotype subtypes of AML, in addition to the well-known prognostic role.