Two-color NPM-ALK FISH of t(2; 5)-positive (A) and -negative (B,C) NHL samples. (A) Interphase nuclei prepared from the bone marrow of a t(2; 5)-positive NHL case (accession number 931737) showing adjacent translocation-containing and normal nuclei. (B) Metaphase chromosome preparation from a t(2; 5)-negative NHL illustrating the lack of pairing of green and red signals in an aneuploid tumor. (C) Interphase nuclei prepared from the same tumor as shown in (B) showing the presence of multiple chromosomes 2 and 5 but the absence of the der(5) produced by the t(2; 5). This case (accession number 921332) was initially thought to be t(2; 5)-positive based on classical cytogenetic analysis that revealed an abnormality of distal 2p.