Surgical treatment and long-term outcomes of low-grade myofibroblastic sarcoma: a single-center case series of 15 patients

Background Low-grade myofibroblastic sarcoma (LGMS) is a poorly studied, rare, soft tissue sarcoma. LGMS is characterized by a low malignancy potential, tendency for local recurrence, and low likelihood of distant metastases. However, no studies have reported on the surgical treatment method and its long-term outcomes. Methods We included all patients treated for LGMS at our institution between March 2010 and March 2021. Medical charts were retrospectively reviewed to collect demographic information, as well as information about the clinical course, tumor characteristics, and outcomes. Statistical analysis was performed to identify the factors associated with the recurrence rate. Results Fifteen patients who underwent surgical treatment were enrolled in this study. There were seven cases in the upper extremities, four in the trunk area, three in the lower extremities, and one in the head and neck area. There were no metastatic cases and two cases of local recurrence. Conclusions The incidence of LGMS in the extremities or trunk may be higher than expected based on the current literature. Univariate analysis showed that local tissue invasion and surgical method could be associated with local recurrence. Although further large studies are needed to establish risk factors of local recurrence or extent of resection margins, based on our study, wide local excision under the proper diagnosis is the most important treatment.

A Case Report of RRBP1-ALK Fusion Gene-Positive Epithelioid Inflammatory Myofibroblastic Sarcoma With Collagenous Stroma

Background: Epithelioid inflammatory myofibroblastic sarcoma (EIMS) is a rare variant of inflammatory myofibroblastic tumors with distinct morphological features and malignant clinical behavior. ALK is positive in all EIMS cases, the RANBP2-ALK fusion gene has been detected in most EIMSs, but several RRBP1-ALK and EML4-ALK fusion genes have also recently been reported.Case presentation: Here, we report a case of RRBP1-ALK fusion-positive EIMS in the colon. The patient was a 26-year-old man. A pelvic mass was found in a routine physical examination and was completely resected. Microscopically, the tumor cells were rounded and epithelioid in shape. Diffuse collagenous stroma and focal inflammatory infiltration were present. ALK was positive, with a pattern of cytoplasmic staining with perinuclear accentuation, and the RRBP1-ALK fusion gene was detected by targeted next generation sequencing. The patient began to take crizotinib from October 2019 to July 2020, and the patient is presently in good condition. No synchronous or metachronous metastases was found.Conclusions: EIMSs with different ALK fusion partner genes have unique staining patterns, which may provide clues for diagnosing EIMS. EIMS cases with RRBP1-ALK fusion gene and with diffuse collagenous stroma may have a good prognosis.