ALK-positive large B-cell lymphoma: A study of six cases from an oncopathology center in North India.

Abstract: ALK-positive large B-cell lymphoma (ALK+ LBCL) is a rare neoplasm with an aggressive course and poor therapeutic response to the standard R-CHOP regimen. Owing to its negativity for usual B- and T-cell markers and immunopositivity for epithelial markers, it can be easily misdiagnosed if it is not contemplated. To study the clinicopathological parameters of cases of ALK+ LBCL diagnosed at our institution. A retrospective observational study of ALK+ LBCL was conducted at a tertiary cancer center of North India with cases diagnosed over a period of 3 years. Six cases of ALK+ LBCL were identified. The clinical findings at presentation included mean age of 38.8 years, male-to-female ratio of 5:1, extranodal presentation (1/6 cases), concurrent extranodal and nodal involvement (3/6), nodal presentation (2/6), high serum LDH (5/5), and bone marrow involvement (1/5). Histomorphology of diffuse (100%), alveolar/nested (16.6%), and sinusoidal pattern (1 case upon relapse) and immunoblastic and plasmablastic morphology (100%) and immunopositivity in all cases for ALK-1 protein (100%), CD138 (100%), MUM1 (100%), LCA (100%) along with negativity for EBER-ISH/EBV-LMP1 immunohistochemistry clinched the diagnosis. Fluorescence in situ hybridization analysis for ALK gene rearrangement was detected in 4/4 cases. Four patients received chemotherapy demonstrating relapse in 2 cases: residual disease and no response in one case each, along with death in 2 cases. A high degree of diagnostic suspicion is required for accurate recognition of ALK+ LBCL. Awareness of its histology, immunohistochemistry, and cytogenetics is pivotal for precise identification of this rare entity.