title: IgM expression in paraffin sections distinguishes follicular lymphoma from reactive follicular hyperplasia.
abstract: The trapping of IgM-containing immune complexes (ICs) by follicular dendritic cells (FDCs) serves as an important step in promoting germinal center (GC) formation. Thus, the deposition of IgM-containing ICs on FDCs can be detected by antibodies recognizing IgM. The present investigation provides the first comprehensive report on the IgM staining pattern in follicular lymphoma (FL, n = 60), with comparisons to reactive follicular hyperplasias (RFH, n = 25), demonstrating that immunohistochemical staining for IgM in paraffin-embedded sections seems to be an additional tool for differentiating between FL and RFH. In RFH, IgM highlighted processes of FDCs, with stronger and more compact staining in light than in dark zones, with occasional very dim staining of GC B cells. In FL, IgM expression patterns were of three types. Pattern I (38 cases) stained tumor cells within neoplastic follicles, with no staining of FDCs. Pattern II (15 cases) stained neither tumor cells nor FDCs. Pattern III (7 cases) stained tumor cells with (3 cases) or without (4 cases) IgM expression; however, variable and attenuated IgM expression was observed on FDCs in each case. Interestingly, significant numbers of IgD+ mantle cells were preserved around the neoplastic follicles in these 7 cases. The data suggested that a complete or considerable loss of IgM expression in FDCs, reflecting the loss of IgM-containing ICs in FDCs, is a typical feature of FL. Increased IgM expression by GC B cells can also serve as an indicator of immunophenotypic abnormality in FL.
authors.affiliation: Department of Pathology, Beijing Friendship Hospital, Capital Medical University Beijing, China.
authors.forename: Yuanyuan
authors.initials: Y
authors.lastname: Zheng
authors.affiliation: Department of Pathology, Beijing Friendship Hospital, Capital Medical University Beijing, China.
authors.forename: Xiaoge
authors.initials: X
authors.lastname: Zhou
authors.affiliation: Department of Pathology, Beijing Friendship Hospital, Capital Medical University Beijing, China.
authors.forename: Jianlan
authors.initials: J
authors.lastname: Xie
authors.affiliation: Department of Pathology, Beijing Friendship Hospital, Capital Medical University Beijing, China.
authors.forename: Hong
authors.initials: H
authors.lastname: Zhu
authors.affiliation: Department of Pathology, Beijing Friendship Hospital, Capital Medical University Beijing, China.
authors.forename: Shuhong
authors.initials: S
authors.lastname: Zhang
authors.affiliation: Department of Pathology, Beijing Friendship Hospital, Capital Medical University Beijing, China.
authors.forename: Yanning
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Department of Pathology, Beijing Friendship Hospital, Capital Medical University Beijing, China.
authors.forename: Xuejing
authors.initials: X
authors.lastname: Wei
authors.affiliation: Department of Pathology, Beijing Friendship Hospital, Capital Medical University Beijing, China.
authors.forename: Bing
authors.initials: B
authors.lastname: Yue
mesh_terms: D000328:Adult; D000368:Aged; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D006965:Hyperplasia / Q000175:diagnosis; D007075:Immunoglobulin M / Q000032:analysis / Q000096:biosynthesis*; D007150:Immunohistochemistry / Q000379:methods; D008221:Lymphoid Tissue / Q000473:pathology*; D008224:Lymphoma, Follicular / Q000175:diagnosis*; D008297:Male; D008875:Middle Aged; D016612:Paraffin Embedding
chemical_list: D007075:Immunoglobulin M
keywords: Follicular lymphoma; IgM; follicular dendritic cells; immunohistochemistry; reactive follicular hyperplasia