Low Grade Fibromyxoid Sarcoma: Diagnosis by Detecting FUS-CREB3L2 Fusion Gene Using Reverse Transcription–Polymerase Chain Reaction

Abstract

Low grade fibromyxoid sarcoma (LGFMS) is a rare soft tissue sarcoma first described by Evans (1987) to have bland-looking fibromyxoid features that had been diagnosed as “fibroma” or “fibromatosis” but metastasize. Hyalinizing spindle cell tumor with giant rosettes (HSCT), which was initially reported by Lane et al. (1997), has been considered a histologic variant of LGFMS. Although LGFMS has a metastatic potential, the morphologic distinction of LGFMSs from other benign or low grade fibromyxoid lesions, such as desmoid-type fibromatoses, soft tissue perineurioma and low grade myxofibrosarcoma, is often difficult and problematic. Besides, LGFMS has no specific or characteristic immunohistochemical marker.

It was shown by Storlazzi et al. (2003) that the gene fusion between the FUS on chromosome 16p11.1 and the CREB3L2, also known as the BBF2H7, on chromosome 7q33 was detected by fluorescence in situ hybridization (FISH) and reverse transcription–polymerase chain reaction (RT-PCR) in a classic LGFMS and a HSCT. Subsequently, two larger series by Panagopoulos et al. (2004) and Mertens et al. (2005) also demonstrated the FUS-CREB3L2 fusion gene and a rare variant of the FUS-CREB3L1 to be specific in LGFMSs. The molecular detection of the fusion gene transcripts is thus considered to be useful in diagnosing LGFMSs as used in other translocation-associated soft tissue sarcomas.