[60] TLE1 Expression Is Not Specific for Synovial Sarcoma: A Standard Section Study of 155 Soft Tissue and Bone Neoplasms

K Kosemehmetoglu, JA Vrana, AL Folpe. Hacettepe University Faculty of Medicine, Ankara, Turkey; Mayo Clinic, Rochester, MN

Background: TLE1, a transcriptional repressor essential in hematopoiesis, neuronal differentiation and terminal epithelial differentiation, has recently been shown in a single tissue microarray (TMA) study to be a highly sensitive and specific marker of synovial sarcomas. Expression of TLE1 has not, however, been studied in standard sections of soft tissue and bone tumors. We investigated TLE1 expression in a large series of well-characterized mesenchymal tumors, in order to more fully characterize the range of TLE1 expression.
Design: Standard sections of 155 bone and soft tissue tumors were immunostained for TLE1 (sc-9121, 1:100, Santa Cruz) with Dako Background Reducing Diluent, pretreatment in the Dako PTLink module with EDTA pH 8.0 for thirty minutes @97 degrees C, and Dako Dual Envision+ detection with Dako DAB+ chromogen. Nuclear positivity was scored as negative (<5% of cell positive), 1+ (5-25% of cells positive), 2+ (25-50% of cells positive), and 3+ (>50% of cells positive).
Results: Overall, TLE1 was expressed at 2-3+ in 48 of 155 (31%) tumors, including 14 of 17 (82%) synovial sarcomas. However, 2-3+ TLE1 expression was also seen in 9 of 11 (82%) schwannomas, 2 of 9 (22%) neurofibromas, 4 of 11 (36%) malignant peripheral nerve sheath tumors, 5 of 13 (38%) rhabdomyosarcomas, 7 of 24 (29%) liposarcomas, 2 of 3 (67%) endometrial stromal sarcomas, 2 of 6 (33%) epithelioid sarcomas, 1 of 4 (25%) solitary fibrous tumors, 2 of 5 (40%) undifferentiated pleomorphic sarcomas, 1 of 5 (20%) leiomyosarcomas, and 1 of 8 (13%) lipomas. TLE1 expression was absent in all cases of alveolar soft part sarcoma, chordoma, clear cell sarcoma, Ewing sarcoma, fibrosarcoma, fibroma, gastrointestinal stromal tumor, low grade fibromyxoid sarcoma, myxofibrosarcoma and myoepithelioma.
Conclusions: Our study confirms the excellent sensitivity of TLE1 for synovial sarcoma. However, TLE1 expression is by no means specific for synovial sarcoma, being present in a number of tumors which enter its differential diagnosis, in particular tumors of peripheral nerve sheath origin. Heterogeneity of TLE1 expression likely explains the differences between the present standard section study and the prior TMA study. TLE1 may be of value in the differential diagnosis of synovial sarcoma, but should be used only in the context of a panel of antibodies. Molecular confirmation of synovial sarcoma-associated fusion genes should remain the gold standard for this diagnosis.
Category: Bone & Soft Tissue

Monday, March 9, 2009 11:15 AM

Platform Session: Section E, Monday Morning