[76] TFE3-Positive Perivascular Epithelioid Cell Tumor as a Distinct Entity: Morphological, Immunohistochemical, and Molecular Analyses.

Mio Tanaka, Keisuke Kato, Kiyoshi Gomi, Mariko Yoshida, Kenji Kurosawa, Hisato Kigasawa, Youkatsu Ohama, Glenn Taylor, Yukichi Tanaka. Kanagawa Children's Medical Center, Yokohama, Japan; Ibaraki Children's Hospital, Mito, Japan; Hospital for Sick Children, Toronto, Canada

Background: Perivascular epithelioid cell tumors (PEComas) are mesenchymal tumors composed of perivascular epithelioid neoplastic cells that are immunoreactive for melanocytic and muscle markers. Nine cases of PEComa with TFE3 immunoreactivity (TFE3+ PEComa) are reported in the literature. Recently, we reported a case of PEComa with a SFPQ–TFE3 gene fusion, arising in the sigmoid colon, which was the first report confirming a specific fusion gene in PEComa (Am J Surg Pathol. 2009;33:1416). In the present study, four cases of TFE3+ PEComa, including two previously reported cases (Pediatr Dev Pathol 2005;8:98, and Hum Pathol 2010;41:768), a newly identified case, and our reported case, were examined to clarify the characteristic features of TFE3+ PEComa.
Design: Two of the TFE3+ PEComas examined arose in the orbit, one in the sigmoid colon, and one in the uvea. A histological review, immunohistochemical (IHC) analysis of TFE3, MiTF, gp100, melan-A, and smooth muscle actin (SMA), and the detection of fusion genes with RT–PCR or FISH analyses were performed.
Results: The most striking histological feature was melanin pigmentation, which was observed to various degrees in all the tumors examined. On IHC analysis, all tumors showed immunoreactivity for TFE3 and gp100, but were not immunoreactive for melan-A or MiTF. The sigmoid colon tumor was negative for SMA, whereas the other three tumors were at least partially positive for it. On FISH analysis, split signals for TFE3 were detected in all four tumors. On RT–PCR analysis, a NONO–TFE3 fusion gene was confirmed in one orbital tumor.
Conclusions: All four TFE3+ PEComas examined had common characteristic histological features (melanin pigmentation) and immunohistological features (positive for gp100 and negative for melan-A and MiTF). SFPQ and NONO are closely related pre-mRNA splicing factors, and SFPQ– and NONO–TFE3 are not common among TFE3-related fusion genes. It was interesting that these uncommon fusion genes were detected in this study. Our results suggest that at least a certain subgroup of TFE3+ PEComas constitutes an immunohistochemically and cytogenetically distinct entity among the PEComa family of tumors.
Category: Bone & Soft Tissue

Monday, February 28, 2011 1:00 PM

Poster Session II # 7, Monday Afternoon


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