Low-grade fibromyxoid sarcoma (LGFMS) is a rare fibrous tumor in soft tissues. Evans [1] reported two cases for the first time. It has been proposed that LGFMS, as a kind of independent soft tissue tumor, usually occurs among the young and middle-aged adults (14 ~ 65 years); its incidence for males is higher than females; it mainly occurs in distal limbs and fascia of the body, and is also observed in the shoulder, neck, armpits, hips, neighboring of anus, small mesentery and omentum; the main clinical manifestation shows a painless mass with slow growth located in the deep soft tissue, and a small part are located in the subcutaneous region; nerve pain can also be resulted from the compression of the nerve by large mass. LGFMS can be divided into two types: typical LGFMS as diagnosed with initially and special one as hyalinizing spindle cell tumor with giant rosettes (HSCTGR) accompanied by giant chrysanthemum-like mass. In 1997, Lane[2] first described HSCTGR and considered it as a special subtype of LGFMS, which have been further supported by many subsequent studies[3]. There are primary HSCTGR with LGFMS metastasis, and primary LGFMS with HSCTGR metastasis. It has been reported that both HSCTGR and LGFMS are highly differentiated sarcomas with metastatic potential, which indicates that LGFMS and HSCTGR share a common pedigree. That study also systematically analyzed the pathogenesis, tumor characteristics and biological behaviors of LGFMS and HSCTGR [3].
The final diagnosis of LGFMS mostly depends on pathological examination, and its pathological morphology is generally characterized by clear boundary, grayish white section, and local mucus gelatinous appearance. Large tumors may have cystic changes and generally have no bleeding or necrosis. The histological features include the following points: the fibromyxoid area alternates with the spindle tumor cell area, the tumor nucleus can be slightly heteromorphic, the spindle cell area is vortex-like or palisade-like arranged, and the mitosis is not common. Immunohistochemistry results showed that LGFMS only expressed vimentin; in the process of myofibroblast differentiation, SMA was occasionally positive; Desmin, S-100, CK, EMA and CD34 were not expressed. In the aspect of molecular biology, chromosomal translocations are found in nearly all patients with LGFMS. The t(7;16)(q32-34; p11) chromosomal translocation and the resulting fusion of FUS RNA binding protein (FUS)–cAMP responsive element binding protein 3-like 2 (CREB3L2) is the most frequently seen (75–95% of patients with LGFMS), whilst the FUS–CREB3L1 fusion gene is present in approximately 5% of cases of LGFMS[4, 5]. Both the CREB3L2 and CREB3L1 genes encode transcription factors[6]. A single-centre retrospective review of 14 patients with LGFMS found no association between the presence of the FUS–CREB3L2 fusion gene and local recurrence or metastatic disease [4].
At present, there is no specific drug treatment for LGFMS, and surgical resection is the only way for the treatment. LGFMS progresses slowly and the mass can last for several years. However, local recurrence can occur once or more after surgery, and the tumor can be even transferred to the lung for some patients. For patients with metastasis, surgical resection of the tumor is still the most effective method[4], while radiotherapy and chemotherapy have no obvious benefits in reducing the recurrence, metastasis and prolonging the survival time of LGFMS patients [7]. In a case series of 36 patients with LGFMS treated with surgical resection with curative intent, 5- and 15-year local control rates were 83% and 79%, respectively [5]. There are currently no putative prognostic biomarkers for LGFMS; however, the FUS–CREB3L2 and FUS–CREB3L1 fusion genes, as well as the pathways influenced by the CREB3L2 and CREB3L1 wild-type genes, may be helpful in building a greater understanding of the pathogenesis of this rare tumour type and in developing effective therapeutic agents. For the above patients, rapid intraoperative pathology is recommended to be performed before determining the tumor nature. The tumor should be completely resected with intact envelope, and then whether the expanded resection of the surrounding tissues is needed or not will be decided according to the pathological results. Simultaneously, the long-term follow-up is also significant for the treatment.