Unlike NPM1-ALK, other ALK fusion proteins (e.g., TPM3-ALK, ATIC-ALK, CLTC-ALK and TFGS/L-ALK) do not localise within the nucleus; 15–25% of ALK positive ALCL do not exhibit immunohistochemical (IHC) staining patterns of ALK in the nucleus with expression restricted instead to the cytoplasm [18]. This evidence concerns the gene NPM1 and anaplastic large cell lymphoma.