ALK-positive Large B-Cell Lymphoma With Multiple Epithelial Antigen Expression and PABPC1::ALK Fusion A Novel Molecular Alteration

Anaplastic lymphoma kinase (ALK)-positive large B-cell lymphoma (LBCL) is a very rare type of LBCL with an aggressive clinical course and poor prognosis. This diagnosis can be challenging given the varied morphology (immunoblastic, plasmablastic, or anaplastic), frequent lack of B-cell antigens, and especially in cases with expression of epithelial antigens. Here, we report a case of ALK-positive LBCL with unusual expression of 4 epithelial-associated markers (AE1/AE3, CK8/18, EMA, and GATA3) and novel poly(A) binding protein cytoplasmic 1 (PABPC1)::ALK fusion which has not been previously reported in this entity. This case also emphasizes the use of comprehensive immunophenotyping that includes multiple lineage-specific antibodies when faced with a malignancy without a clear differentiation to avoid misdiagnosis. This case only achieved partial response to combination chemotherapy, radiation, and ALK inhibitor regimens, and furthers our understanding of this uncommon lymphoma.

Automated summary

ALK-positive large B-cell lymphoma (LBCL) is a rare and aggressive type of LBCL with poor prognosis. This case report highlights a unique expression of epithelial-associated markers and a novel PABPC1::ALK fusion gene in ALK-positive LBCL. It also emphasizes the importance of comprehensive immunophenotyping to avoid misdiagnosis and contributes to the understanding of this uncommon lymphoma.