title: IgG3 subclass-positive primary thymic MALT lymphoma without trisomy 3 and trisomy 18: report of a case and review of literature.
abstract: The patient, a 42-year-old man, was diagnosed as having an anterior mediastinal tumor. Examination of the resected tumor showed findings consistent with a primary thymic mucosa-associated lymphoid tissue lymphoma, stage IA. Postoperative (18)F-fluorodeoxyglucose-positron emission tomography/computed tomography demonstrated fluorodeoxyglucose accumulation at the site of tumor excision. This accumulation was interpreted as representing a residual lesion, and the patient was treated with rituximab. The patient has since been in a state of complete remission for about 3 years. Sporadic mucosa-associated lymphoid tissue lymphoma cells that appeared to have a propensity for differentiating into plasma cells in this case were analyzed for IgG and IgG subclass expression by immunohistochemical staining. The mucosa-associated lymphoid tissue lymphoma cells that showed a propensity for differentiating into IgG-positive plasma cells were IgG3-positive and IgG1-, IgG2- and IgG4-negative. An increase in IgG3 or IgG1 expression in immune cells has been previously demonstrated in immune responses to continuous exposure to the same proteins or peptide antigens and most mucosa-associated lymphoid tissue lymphomas show increased IgG3 and/or IgG1 expression. It is consistent with the fact that inflammation due to stimulation by a pathogenic antigen is considered to be etiologically responsible for the development of mucosa-associated lymphoid tissue lymphoma.
authors: Department of Hematology, Juntendo University Urayasu Hospital Chiba, Japan.
authors: Kei-Ji
authors: KJ
authors: Sugimoto
authors: Department of Human Pathology, Juntendo University School of Medicine Tokyo, Japan.
authors: Miki
authors: M
authors: Asahina
authors: Department of Hematology, Juntendo University Urayasu Hospital Chiba, Japan.
authors: Asami
authors: A
authors: Shimada
authors: Department of Hematology, Juntendo University Urayasu Hospital Chiba, Japan.
authors: Kunimoto
authors: K
authors: Ichikawa
authors: Department of Hematology, Juntendo University Urayasu Hospital Chiba, Japan.
authors: Mutsumi
authors: M
authors: Wakabayashi
authors: Department of Hematology, Juntendo University Urayasu Hospital Chiba, Japan.
authors: Yasunobu
authors: Y
authors: Sekiguchi
authors: Department of Pathology, Juntendo University Urayasu Hospital Chiba, Japan.
authors: Hiroshi
authors: H
authors: Izumi
authors: Department of Pathology, Research Hospital, The Institute of Medical Science, the University of Tokyo Japan.
authors: Yasunori
authors: Y
authors: Ota
authors: Department of Hematology, Juntendo University School of Medicine Tokyo, Japan.
authors: Norio
authors: N
authors: Komatsu
authors: Department of Hematology, Juntendo University Urayasu Hospital Chiba, Japan.
authors: Masaaki
authors: M
authors: Noguchi
mesh_terms: D000328:Adult; D002887:Chromosomes, Human, Pair 18 / Q000235:genetics; D002893:Chromosomes, Human, Pair 3 / Q000235:genetics; D006801:Humans; D007074:Immunoglobulin G / Q000276:immunology*; D007150:Immunohistochemistry; D018442:Lymphoma, B-Cell, Marginal Zone / Q000276:immunology / Q000473:pathology*; D008297:Male; D008479:Mediastinal Neoplasms / Q000276:immunology / Q000473:pathology; D010950:Plasma Cells / Q000276:immunology / Q000473:pathology; D013953:Thymus Neoplasms / Q000276:immunology / Q000473:pathology*; D014314:Trisomy
chemical_list: D007074:Immunoglobulin G
keywords: IgG1; IgG3; Mucosa-associated lymphoid tissue (MALT) lymphoma; paraffin-embedded tissue section-fluorescence in situ hybridization (PS-FISH); thymus