ALK-positive large B-cell lymphoma presenting in the nasal cavity with CLTC::ALK fusion: a case report of alectinib-integrated therapy followed by autologous hematopoietic stem cell transplantation.

Anaplastic lymphoma kinase-positive large B-cell lymphoma (ALK+ LBCL) is a rare and aggressive lymphoma for which no standard frontline treatment has been established. Presentation in the nasal cavity is particularly uncommon. We report the case of a 39-year-old man who presented with progressive left-sided nasal obstruction, epistaxis, and bilateral cervical lymphadenopathy. Imaging revealed a left sinonasal/nasopharyngeal mass, bilateral cervical lymphadenopathy, diffuse skeletal hypermetabolism, markedly elevated lactate dehydrogenase, and focal bone marrow involvement. Histopathologic examination showed a plasmablastic neoplasm with strong granular cytoplasmic ALK expression. The tumor cells were positive for CD138, MUM1, EMA, and kappa light chain, but negative for CD20, CD19, CD79a, CD3, CD30, CD56, and EBER. Fluorescence in situ hybridization confirmed ALK rearrangement, and RNA sequencing together with RT-PCR identified a CLTC::ALK fusion (CLTC exon 31::ALK exon 20). The patient was diagnosed with Ann Arbor stage IVB ALK+ LBCL. Disease progression after initial CVAD chemotherapy and persistent disease after CVAD-E prompted the addition of alectinib from cycle 3, with complete metabolic response on PET-CT after cycle 4. Consolidation with Hyper-CVAD plus concurrent alectinib was followed by autologous hematopoietic stem cell transplantation (auto-HSCT) and post-transplant alectinib maintenance. The patient remains in complete remission 10 months after diagnosis. This case illustrates the diagnostic value of integrated morphologic and molecular assessment in CD20-negative plasmablastic lymphoid neoplasms and suggests that incorporating ALK inhibition into multimodal therapy may be a reasonable strategy for selected patients with ALK+ LBCL.