A Novel del(20q) in Aggressive Nodal Marginal Zone Lymphoma

This is a case report of a previously undescribed 20q chromosomal deletion (del(20q)) in marginal zone lymphoma (MZL). A 54-year-old Caucasian male presented with an enlarging neck mass and multiple violaceous skin nodules over his chest. Biopsy of the neck mass and cervical lymph nodes revealed MZL. Cytogenetic evaluation of both lymph node and bone marrow tissue revealed del(20q). This was an unexpected finding, as del(20q) is associated with myelodysplastic syndromes and myeloproliferative neoplasms and rarely seen in diffuse large B-cell lymphoma, follicular lymphoma, and T-cell lymphoma, but has not previously been described in MZL. We describe the case presentation and histologic findings and discuss the significance of this novel finding.


Introduction
20q chromosomal deletion (del(20q)) is a well-described cytogenetic abnormality in myeloid neoplasms such as myelodysplastic syndrome (MDS), acute myeloid leukemia (AML), and the myeloproliferative neoplasms (MPN) [1]. Del(20q) is rare in lymphomas, but has been detected in cases of diffuse large B-cell lymphoma, follicular lymphoma, and T-cell lymphoma [1]. A literature search and the National Cancer Institute's Recurrent Chromosome Aberrations in Cancer Database failed to reveal any reported cases of del(20q) in marginal zone lymphoma (MZL) [2]. Here we present the first reported case of MZL with del(20q), detected by FISH in lymph node tissue and by karyotyping in involved bone marrow tissue.

Case Presentation
The patient is a 54-year-old Caucasian man with a slowly enlarging neck mass, accompanied by multiple violaceous skin nodules over his chest and neck and B symptoms. Physical exam revealed an 11 × 8 cm tender, erythematous right neck mass as well as multiple violaceous, mobile skin nodules on the neck and chest. Splenomegaly was not present. Also of note, the patient is hepatitis C virus positive, which is associated with MZL [3]. A CT of the neck revealed a large, poorly defined right neck mass measuring up to 9 cm as well as many enlarged cervical lymph nodes. An open biopsy was performed and a right posterior cervical lymph node and tissue from the deep neck mass were sent for histologic evaluation.
Microscopic examination showed almost complete effacement of the node (Figure 1(A)). Follicles were replaced by atypical monocytoid cells (Figures 1(B) and 1(C)), which stained positive for PAX-5, CD19, and CD20, but were negative for CD5 and cyclin D1. The effaced area had a MIB-1 labeling index of 10%. BCL-6 and CD23 were diffusely positive in remnant germinal centers which were replaced by atypical monocytoid cells, and these areas corresponded with a negative CD10. These morphologic and immunohistochemical (IHC) findings are characteristic of a nodal MZL [3,4].The tissue from the deep neck mass revealed similar histology but an area with larger, more hyperchromatic cells (Figures 1(D) and 1(E)) and a higher mitotic rate, with a MIB-1 labeling index of up to 70% (Figure 1(F)). The neoplastic lymphocytes invaded beyond the capsule into the surrounding muscle, consistent with an aggressive morphology [4]. Flow cytometry of the neck mass revealed a monoclonal B-cell population expressing kappa immunoglobulin light chains, CD19 and CD20.
Punch biopsy of one of the skin nodules (Figure 2(A)) showed diffuse involvement of the dermis (Figure 2(B)). The histology showed mostly small monocytoid B cells (Figure 2(C)), again with a classic MZL immunophenotype: BCL6 and CD23 positive in remnant follicles replaced by atypical CD20 positive monocytoid B cells.
Both lymph node and bone marrow tissues were sent for cytogenetic evaluation. FISH on representative lymph node tissue revealed del(20q), near 20q12 (Figure 3(A)). There was not morphologic evidence of MZL in the bone marrow nor any myeloid neoplasm or other 20q deletionassociated disease identified. However, a karyotype of the bone marrow aspirate also revealed a del(20q), near 20q11.2 (Figure 3(B)). This may represent an enrichment of MZL cells during cell culture and molecular evidence of MZL involvement in the bone marrow. The patient was treated  with bendamustine plus rituximab and responded well with a complete remission.
The finding of a del(20q) in both the lymph node tissue and bone marrow samples was an unexpected finding in this case; a diagnosis of nodal MZL could confidently be made by lymph node histological features, IHC and flow cytometric immunophenotyping. The literature has not previously reported del(20q) in MZL. This finding may represent a specific cytogenetic abnormality in this nodal MZL with an aggressive morphology and high-stage disease. In conclusion, this case of nodal MZL with 20q deletion is a novel finding which can expand the breadth of knowledge of chromosomal abnormalities in MZL.