title: Follicular dendritic cells in extranodal non-Hodgkin lymphomas of MALT and non-MALT type.
abstract: Extranodal lymphomas of the thyroid (n = 19), kidney (n = 15) and testis (n = 30) were investigated histologically and immunohistochemically for follicular dendritic cell pattern using the monoclonal antibody Ki-FDClP. This recognizes follicular dendritic cells in paraffin sections. Follicular dendritic cells were most predominant in lymphomas of the thyroid. These thyroid lymphomas showed the morphological features of mucosa-associated lymphoid tissue (MALT) type lymphomas in 18 of 19 cases and were classified as high-grade malignant lymphoma of MALT type with evidence of a low-grade malignant component (n = 18). Ten of these cases contained destroyed reactive follicles of follicular dendritic cells. In 6 of these 10 cases follicular dendritic cells occurred in a pattern of tumour-associated abortive follicle type. The remaining lymphoma of the thyroid was an immunoblastic lymphoma of B-cell type showing no detectable follicular dendritic cells. In extranodal lymphomas of non-MALT type follicular dendritic cells occurred in only two cases where immunocytoma involved the kidney. Malignant lymphomas of the kidney (chronic lymphocytic leukaemia, n = 2; immunocytoma, n = 4; centroblastic lymphoma, n = 9) and of the testis (immunocytoma, n = 2; centroblastic lymphoma, n = 27; immunoblastic lymphoma of B-cell type, n = 1) revealed no characteristics of MALT type lymphoma, cytologically or with respect to follicular dendritic cells. Classical lymphoepithelial lesions formed by centrocyte-like cells, a hallmark of MALT, occurred exclusively in thyroid lymphomas of MALT type. Although occurrence of classical lymphoepithelial lesions formed by centrocyte-like cells was limited to thyroid lymphomas of MALT type, a growth pattern of lymphoid blasts, with formation of lesions mimicking lymphoepithelial lesions superficially, was found in 6 of 27 testicular centroblastic lymphomas. Follicular dendritic cells in non-Hodgkin's lymphomas of MALT type show distinct follicular patterns not found in other extranodal lymphomas such as those found in the kidney and testis.
authors.affiliation: Institute of Pathology, School of Medicine, Technical University of Munich, Germany.
authors.forename: C
authors.initials: C
authors.lastname: Fellbaum
authors.forename: J
authors.initials: J
authors.lastname: Sträter
authors.forename: M L
authors.initials: ML
authors.lastname: Hansmann
mesh_terms: D003713:Dendritic Cells / Q000473:pathology*; D006801:Humans; D007680:Kidney Neoplasms / Q000473:pathology*; D008228:Lymphoma, Non-Hodgkin / Q000145:classification* / Q000473:pathology*; D008297:Male; D013736:Testicular Neoplasms / Q000473:pathology*; D013964:Thyroid Neoplasms / Q000145:classification / Q000473:pathology*