High‐grade B cell lymphoma, unclassifiable, with blastoid features: an unusual morphological subgroup associated frequently with BCL2 and/or MYC gene rearrangements and a poor prognosis

Kanagal‐Shamanna R, Medeiros L J, Lu G, Wang S A, Manning J T, Lin P, Penn G M, Young K H, You M J, Vega F, Bassett R & Miranda R N (2012) Histopathology 61, 945–954 High‐grade B cell lymphoma, unclassifiable, with blastoid features: an unusual morphological subgroup associated frequently with BCL2 and/or MYC gene rearrangements and a poor prognosis Aims: A subset of B cell lymphomas with blastoid features do not fit either as B lymphoblastic lymphoma/leukaemia or blastoid mantle cell lymphoma. Their classification is challenging, even with complete clinicopathological and genetic information. At a haematopathology workshop, experts had suggested the term ‘high‐grade B cell lymphoma, unclassifiable, with blastoid features’, and recommended further studies. Methods and results: We describe the clinicopathological, immunophenotypic and cytogenetic findings of 24 high‐grade B cell lymphomas, unclassifiable, with blastoid features. Fifteen patients presented de novo and seven patients had a history of lymphoma. Twenty patients (83%) presented with nodal disease. All tumours expressed pan‐B cell antigens and 17 (89%) of 19 tumours assessed had a germinal centre B cell immunophenotype. Ten (63%) of 16 tumours assessed by fluorescence in‐situ hybridization (FISH) had MYC rearrangement, 13 of 18 (72%) carried IGH ‐ BCL2 and nine of 15 (60%) had both (double‐hit lymphoma). The median overall survival was 1.1 years. Using 2008 World Health Organization criteria, 15 cases were classified as B cell lymphoma, unclassifiable, with features intermediate between diffuse large B cell lymphoma (DLBCL) and Burkitt lymphoma, and nine as DLBCL, small centroblastic variant. Conclusion: High‐grade B cell lymphomas, unclassifiable, with blastoid features are clinically aggressive with poor survival. Most neoplasms have a germinal centre B cell phenotype. MYC rearrangements and IGH‐BCL2 are common, and ∼60% are double‐hit lymphomas.