Histologic, immunophenotypic, and molecular cytogenetic findings. An example of hematoxylin and eosin (A) and ALK1 (B) staining performed in case 3 showing, respectively, a massive proliferation of plasmablast-like cells and a granular cytoplasmic localization of ALK. FICTION with LSI ALK and ALK1 (blue) (C), or anti-IgA (blue) (case 1) (D), and anti-IgG (case 2) (E). Metaphase FISH with ALK P1 (1111H1) (green) and BAC 758H9 (CLTC) (red) in case 1 (F) and case 2 (G). Arrowhead and arrow indicate the der(2) and der(17), respectively. Inset in panel F: WCP2 (green) and WCP17 (red). Note 1F2O1G FISH signals in case 1 (C-D) pointing the ALK gene rearrangement in ALK1⁺/IgA⁺ cells. Extra red signal possibly reflects an additional copy of the der(17) chromosome. Original magnifications: × 200 (A-B); × 630 (C-G).