title: BCL-6 expression in mesenchymal tumours: an immunohistochemical and fluorescence in situ hybridisation study.
abstract: The BCL-6 proto-oncogene encodes a transcriptional repressor protein. Among normal tissues, BCL-6 expression is confined to germinal center B-cells and a subpopulation of T-helper cells. Little is known about BCL-6 expression in mesenchymal tissues. We examined a series of solitary fibrous tumor (SFT) and other mesenchymal tumors for BCL-6 expression. Immunohistochemistry for BCL-6 was performed on 64 mesenchymal tumors [26 SFT (19 benign/uncertain, 7 malignant), 6 synovial sarcomas (SS), 5 gastrointestinal stromal tumors (GIST), 5 malignant peripheral nerve sheath tumors (MPNST), 5 leiomyosarcomas (LMS), 9 leiomyomas (LM) 4 desmoid tumors (DT), 4 perineuriomas (PN)]. Nuclear immunoreactivity was considered positive. Six BCL-6 positive SFT were also tested for BCL-6 gene rearrangement/amplification by FISH. Nuclear expression of BCL-6 was seen in 13/26 SFT, 5/5 LMS, 1/9 LM, 5/6 SS, 1/5 GIST, 1/5 MPNST, 1/4 PN, and 0/5 DT. BCL-6 expression was significantly more frequent in malignant (6/7) as compared with benign/uncertain SFT (6/19) (p=0.02) and in LMS (5/5) as compared with LM (1/9) (p=0.003). FISH for BCL-6 rearrangement/amplification was negative in all tested cases. We have observed BCL-6 expression in 50% or more of SFT, SS, and LMS, and in a lesser percentage of LM, GIST, MPNST and PN. Significantly more frequent expression of BCL-6 in malignant compared with benign/uncertain SFT and in LMS compared with LM suggests abnormalities in the BCL-6 signaling pathway may contribute to malignant transformation in at least some mesenchymal tumors. It is unlikely that BCL-6 expression in mesenchymal tumors is due to BCL-6 gene amplification or rearrangement.
authors: Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, Minnesota 55905, USA.
authors: Matthew P
authors: MP
authors: Walters
authors: Ellen D
authors: ED
authors: McPhail
authors: Mark E
authors: ME
authors: Law
authors: Andrew L
authors: AL
authors: Folpe
mesh_terms: D014408:Biomarkers, Tumor / Q000032:analysis* / Q000235:genetics*; D002471:Cell Transformation, Neoplastic / Q000737:chemistry / Q000235:genetics; D004268:DNA-Binding Proteins / Q000032:analysis* / Q000235:genetics*; D005784:Gene Amplification; D015321:Gene Rearrangement; D006801:Humans; D007150:Immunohistochemistry; D017404:In Situ Hybridization, Fluorescence; D008648:Mesoderm / Q000737:chemistry* / Q000473:pathology; D008910:Minnesota; D009372:Neoplasms, Connective Tissue / Q000737:chemistry* / Q000235:genetics* / Q000473:pathology; D000090063:Proto-Oncogene Mas; D051560:Proto-Oncogene Proteins c-bcl-6; D054364:Solitary Fibrous Tumors / Q000737:chemistry / Q000235:genetics
chemical_list: C084103:BCL6 protein, human; D014408:Biomarkers, Tumor; D004268:DNA-Binding Proteins; C000715470:MAS1 protein, human; D000090063:Proto-Oncogene Mas; D051560:Proto-Oncogene Proteins c-bcl-6