The Research Of Morphology And Molecular Cytogenetic Alterations In Follicular Dendritic Cell Sarcoma

Objectives:To enhance the awareness and diagnosis of follicular dendritic cell sarcoma by analyzing the morphological and molecular cytogenetic features of follicular dendritic cell sarcoma, which provide for finally understand the development and progression of this tumor.Methods:Formalin-fixed, paraffin-embeded (FFPE) samples of 6 cases of follicular dendritic cell sarcomas were retrieved from the files of the Department of Pathology, Xiangya Hospital of Central South University and other hospitals, between the years 2004 and 2009. Their pathological diagnoses were confirmed again.①Six cases of follicular dendritic cell sarcomas were investigated by light microscope and immunohistochemical staining with review of the related literatures.②In situ hybridization for Epstein-Barr virus (EBV)-encoded RNA (EBER) was performed on paraffin sections using an EBER in situ hybridization and detection kit.③The whole-genome DNA of 4 cases were extracted from formalin-fixed and paraffin-embeded tissue section. Array-comparative genomic hybridization(aCGH) was performed in 4 cases to screen DNA copy number changes in whole genomes.Results:①Morphological features of FDCS:the tumor was composed of oval to spindle cells, arranging in storiform, whorled, and fasciclar patterns. Individual cells possessed characteristic features, including slightly eosinophilic, fibrillary cytoplasm, a delicate nuclear membrane, vesicular nuclei, small but distinct nucleoli and indistinct cell borders. A constant and highly characteristic feature was the sprinkling throughout the entire tumor of small lymphocytes.②Immunohistochemically, neoplastic cells were strongly immunoreactive for CD21,CD35 and CD23.③The evidence of Epstein-Barr virus was not found by in situ hybridization for EBER-1 gene.④Four cases with follicular dendritic cell sarcoma showed evidences of increased or decreased DNA sequence copy numbers involving one or more regions of the genome. The frequently amplification of chromosome segments of FDCS were lOq1l,15q11 and 21p11, while the frequently loss chromosome segments were not observed.⑤The frequently amplification of genes were BCL8(15q11-13), POTEB (15q11.2), TPTE(21p11), while the frequently loss genes were not found.Conclusions: ①The histological feature of FDCS is consistent with the observation in the previous literatures:oval to spindle cells with elongated nuclei, delicate, dispersed chromatin and pale eosinophilic cytoplasm. Scattered multinucleated tumor cells may also be present.②CD21, CD35, combined with CD 23, are the most widely used markers for diagnosis of follicular dendritic cell sarcoma.③The clinicopathological significance of the LMP-1 gene in FDCS warrants further investigation, the role of EBV remains unclear in the pathogenesis of FDC tumors.④Gained l0qll,15q11 and 21p11 may be correlated with follicular dendritic cell sarcoma.⑤BCL8(15q11-13) may be involved in the development and progression of FDCS.