A huge gluteal mass diagnosed as CIC-rearranged sarcoma: a rare case report and literature review.

Capicua transcriptional repressor (CIC)-rearranged sarcoma, also known as CIC-rearranged sarcoma (CRS), is a recently recognized sarcoma subtype characterized by specific molecular features. It is associated with aggressive clinical course and a poor prognosis. Here, we present a rare case of CRS, including a detailed clinical, pathological, and molecular analysis, to enhance understanding of this disease and provide a reference for future diagnosis and treatment. A 15-year-old female adolescent initially presented with a rapidly growing mass in her left buttock, accompanied by intermittent pain. A magnetic resonance imaging (MRI) scan revealed a 12.7 × 8.6 × 11.9 cm mixed-intensity mass, suggesting a mesenchymal sarcoma. After histological and immunohistochemical analysis, a preliminary diagnosis of malignant small round cell tumor was made, which was later confirmed as CRS by Fluorescence in situ hybridization (FISH). A course of VDC/IE regimen was administered as first-line neoadjuvant chemotherapy. However, a follow-up MRI showed a 28% increase in tumor volume. Given the poor response to chemotherapy, we decided to perform a wide resection surgery. Unfortunately, lung metastases developed only one month postoperatively, and local recurrence occurred two months postoperatively. The patient then underwent concurrent chemoradiotherapy. At the time of data cutoff, the patient achieved a stable disease state and retained satisfactory walking function. In conclusion, treatment paradigms for CRS have yet to be defined. For patients with large tumor volumes, preoperative neoadjuvant chemotherapy may be ineffective and could potentially delay more effective treatment. Early surgical resection is probably a more suitable treatment option. Multidisciplinary collaboration is essential in the treatment of CRS, and large studies exploring novel therapeutic options are urgently needed to bring hope to patients with this aggressive disease.