Relapsed anaplastic lymphoma kinase-positive large B-cell lymphoma expressed cluster of differentiation 4 and cytokeratin: An initially misdiagnosed case corrected by immunoglobulin κ locus gene rearrangement detection.

Anaplastic lymphoma kinase (ALK)-positive large B-cell lymphoma (LBCL) is a rare lymphoma subtype. The present study investigated a refractory nodal ALK-positive LBCL case in a 28-year-old Chinese male. It was initially misdiagnosed as ALK-positive anaplastic large cell lymphoma; however, the patient's lesions relapsed and spread widely following a short remission for chemotherapy and the patient succumbed to the disease 3 months' post-autologous stem cell transplantation; thus, a revision was performed. Histologically, the tumor cells exhibited a characteristic immunoblastic morphology with marked cellular pleomorphism. All lesions shared the same immunoprofiles, including granular cytoplasmic ALK staining patterns and a lack of cell lineage-associated markers, with the exception of cluster of differentiation (CD)45 and CD4. CD30 expression was revealed to be negative and CD138 staining was observed to be positive, additionally, cytokeratin was expressed aberrantly in a relapsed tumor biopsy. Fluorescence hybridization studies demonstrated breakage and extra copies of the gene in ≥30% of cells. Final clarification was provided by the detection of immunoglobulin κ locus () gene rearrangement in clonality studies [but notimmunoglobulin heavy locus () and immunoglobulin λ locus () genes]. This aggressive entity requires distinct modalities of standard treatment, and may be ignored owing to its rarity in routine pathology laboratories. BIOMED-2 polymerase chain reaction assays, including for , and genes, are essential for the detection of gene rearrangement.