NPM1 and anaplastic large cell lymphoma: ALK immunostainning of NPM-ALK-positive ALCL cases shows a characteristic cytoplasmic and nuclear distribution of the chimeric ALK protein that is due to hetero-oligomerization of NPM-ALK and normal NPM, a phosphoprotein that normally shuttles ribonucleoproteins between the cytoplasm and nucleus, but can aberrantly transport NPM-ALK to the nucleus [12]; whereas patients with the variant-ALK fusion proteins demonstrate cytoplasmic staining only [13,14].