PB1826 COMPOSITE LYMPHOMA CONTAINING MANTLE CELL AND PERIPHERAL T‐CELL LYMPHOMA, NOT OTHERWISE SPECIFIED: A REPORT OF 2 CASES TREATED WITH UP‐FRONT AUTOLOGOUS STEM CELL TRANSPLANTATION.
Authors: González‐Gascón Y Marín I. , Menarguez J. , Kwon M. , Burdaspal A. , Martinez‐Laperche C. , Castro Y. , Infante M.S. , Diez‐Martín J.L. , Hernández Rivas J.A. 
Published: June 2019

Background:Composite lymphomas are a rare entity defined by the presence of two different lymphomas in the same patient and in the same organ.Aims:To describe two cases of composite lymphoma comprising mantle‐cell lymphoma (MCL) and peripheral T‐cell lymphoma, not otherwise specified (PTCL, NOS), a very rare association which has only been reported twice in the literature.Methods:Retrospective review of two clinical cases.Results:Case 1: A 64‐year‐old woman presented with B symptoms, massive splenomegaly and systemic lymphadenopathy. Immunohistochemical studies of a lymph node biopsy suggested the presence of two lymphomas, a predominant component of a PTCL, NOS and an in situ mantle cell neoplasia. Fluorescence in situ hybridization (FISH) performed on the paraffin embedded tissue sections confirmed the presence of t(11;14), and a TCRα rearrangement. A monoclonal peak was detected in the IGH PCR analysis. PCR for TCRγ chain also showed a monoclonal peak. The bone marrow biopsy showed a scant infiltration of T‐cells compatible with that seen in the lymph node, with the same TCR rearrangement, suggesting PTCL, NOS infiltration. The patient received six cycles of Rituximab‐CHOP achieving a complete response, and was consolidated with an ASCT. She remained in complete remission for five years, when she relapsed with pancytopenia. Bone marrow biopsy in this moment showed a nodular and interstitial infiltration by small lymphocytes consisting of 40% of total cellularity. Identical IGH gene rearrangement to the one present at the moment of diagnosis, in addition to t(11;14) (FISH) were detected, suggesting a late relapse of the MCL component. Relapse was limited to the bone marrow and the patient started treatment with Ibrutinib achieving a partial response. Recently, Ibrutinib has been discontinued due to different grade 3 infectious complications and the patient remains in partial response without active treatment. Case 2: A 45‐year‐old man presented with an enlarged right tonsil. There were no palpable lymph nodes or B symptoms associated. Image studies confirmed right tonsillar hyperplasia without other findings, and an excisional biopsy was performed to clarify the diagnosis. Contrary to case 1, the biopsy suggested a predominant infiltration of a classical MCL, and an atypical proliferation of T‐cells. Both PCR of IGH and TCR‐γ genes showed the presence of clonal populations. FISH showed CCND1/IGH and TCRα rearrangements. Bone marrow involvement by MCL was confirmed by biopsy. A diagnosis of composite lymphoma (PTCL, NOS and MCL) was stablished. The patient received 3 cycles of Rituximab‐Hyper‐CVAD regimen achieving complete remission. An ASCT was performed to consolidate the response without significant complications. Four years later, he remains free of disease with no later side effects.Summary/Conclusion:The diagnosis of composite lymphomas is challenging and requires a multidisciplinary approach including cytological, immunohistoquemical, cytogenetic and molecular techniques. Treatment aimed to target the most aggressive component of the composite lymphoma is mandatory to achieve a successful result.