The clinicopathological spectrum of sclerosing epithelioid fibrosarcoma: report of an additional series with review of the literature

Rare case report: sclerosing epithelioid fibrosarcoma with FUS-CREB3L1 gene fusion

Sclerosing epithelioid fibrosarcoma (SEF) is a rare soft tissue malignancy frequently misdiagnosed due to its overlapping immunohistochemical and molecular features with low-grade fibromyxoid sarcoma (LGFMS). We present the case of a 60-year-old male who initially presented with a mass in the left thigh four years ago, which significantly increased in size over the past year. MRI of the femur revealed a large, well-circumscribed mass in the mid and lower left thigh. Surgical excision of the tumor and associated thrombus in the ipsilateral blood vessel was performed. Histomorphological analysis confirmed a pure SEF with no myxoid stroma, aiding in its differentiation from LGFMS. Immunohistochemical staining revealed diffuse and strong MUC4 positivity, while next-generation sequencing (NGS) demonstrated molecular characteristics consistent with LGFMS, specifically FUS-CREB3L1 gene fusion. This case underscores the asynchrony between the pathological morphology and molecular features of soft tissue tumors during their development and differentiation. Although histologically low-grade, SEF typically exhibits a high rate of local recurrence and distant metastasis. We diagnosed this case as SEF and recommended an aggressive clinical treatment regimen. This report aims to raise awareness of the diagnostic challenges associated with SEF and LGFMS.

Metastatic Sclerosing Epithelioid Fibrosarcoma at Diagnosis: A Case Report

Sclerosing epithelioid fibrosarcoma (SEF) is a rare and aggressive neoplasm composed of epithelioid cells arranged in strands and nests embedded in a highly sclerotic collagenous stroma. We report a case of a 36-year-old man who started with lumbar pain, with extension to both legs, night sweats, and weight loss. He underwent magnetic resonance imaging (MRI) of the lumbar spine; computed tomography (CT) scan of the chest, abdomen, and pelvis; and [18F]-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) scan. The CT scan revealed a 13 cm thoracic mass, the MRI presented with diffuse neoplastic invasion of the vertebrae, and the PET showed hepatic, bone, and possibly pulmonary metastases. The histological diagnosis was compatible with SEF. The disease progressed very quickly, namely, with an episode of spinal cord compression, which made the patient paraplegic. He underwent surgery and, subsequently, radiotherapy (RT). Due to the clinical and analytical evolution, it was not possible to initiate systemic treatment and the patient ultimately passed away. In conclusion, SEF is an aggressive type of sarcoma that affects middle-aged patients, with high rates of distant metastases and mortality. The usual treatment is surgery followed by either radiotherapy or chemotherapy. However, further clinical trials are needed to find more systemic target therapies.

Sclerosing epithelioid fibrosarcoma of the pancreas: A case report

BACKGROUND

A sclerosing epithelioid fibrosarcoma (SEF) is a rare malignant fibroblastic soft tissue tumor that rarely occurs in intra-abdominal organs. A case of a SEF in the pancreatic head is reported herein, including its clinical manifestations, preoperative imaging features, gross specimen and pathological findings.

CASE SUMMARY

A 33-year-old male patient was admitted to Peking Union Medical College Hospital in December 2023 due to a one-year history of intermittent upper abdominal pain and the discovery of a pancreatic mass. The patient underwent an enhanced computed tomography scan of the abdomen, which revealed a well-defined, round mass with clear borders and calcifications in the pancreatic head. The mass exhibited progressive, uneven mild enhancement, measuring approximately 6.6 cm × 6.3 cm. The patient underwent laparoscopic pylorus-preserving pancreaticoduodenectomy. Postoperative pathological examination revealed that the lesion was consistent with a SEF. At the 3-month postoperative follow-up, the patient did not report any short-term complications, and there were no signs of tumor recurrence.

CONCLUSION

SEFs are rare malignant fibrous soft tissue tumors. SEFs rarely develop in the pancreas, and its preoperative diagnosis depends on imaging findings, with confirmation depending on pathological examination and immunohistochemistry. Currently, only four cases of pancreatic SEF have been reported in studies written in English. This case is the first reported case of a pancreatic SEF by a clinical physician.

Sclerosing Epithelioid Fibrosarcoma (SEF) versus Low Grade Fibromyxoid Sarcoma (LGFMS): Presentation and outcome in the nationwide NETSARC+ series of 330 patients over 13 years

Sclerosing Epithelioid Fibrosarcoma (SEF) and Low Grade Fibromyxoid Sarcoma (LGFMS) are ultrarare sarcomas sharing common translocations whose natural history are not well known. We report on the nationwide exhaustive series of 330 patients with SEF or LGFMS in NETSARC+ since 2010.

PATIENTS AND METHODS

NETSARC (netsarc.org) is a network of 26 reference sarcoma centers with specialized multidisciplinary tumor boards (MDTB). Since 2010, (i) pathological review has been mandatory for sarcoma,and (ii) tumour/patients' characteristics have been collected in the NETSARC+ nationwide database. The characteristics of patients with SEF and LGFMS and their outcome are compared.

RESULTS

35/73 (48%) and 125/257(49%) of patients with SEF and LGFMS were female. More visceral, bone and trunk primary sites were observed in SEF (p < 0.001). 30% of SEF vs 4% of LGFMS patients had metastasis at diagnosis (p < 0.0001). Median size of the primary tumor was 51 mm (range 10-90) for LGFMS vs 80 (20-320) for SEF (p < 0.001). Median age for LGFMS patients was 12 years younger than that of SEF patients (43 [range 4-98] vs 55 [range 10-91], p < 0.001). Neoadjuvant treatment was more often given to SEF (16% vs 9%, p = 0.05). More patients with LGFMS were operated first in reference centers (51% vs 26%, p < 0.001). The R0 rate on the operative specimen was 41% in LGFMS vs 16% in SEF (p < 0.001). Median event-free survival (EFS) of patients with SEF and LGFMS were 32 vs 136 months (p < 0.0001). The median overall survival (OS) was not reached. Fifty-months OS was 93% vs 81% for LGFMS vs SEF (p = 0.05). Median OS was 77 months after first relapse, similar for SEF and LGFMS. In multivariate analysis, age, tumor size, metastasis at diagnosis were independent prognostic factors for OS in LGFMS.

CONCLUSIONS

Although sharing close molecular alterations, SEF and LGFMS have a different natural history, clinical presentation and outcome, with a higher risk of metastatic relapse in SEF. Survival after relapse is longer than with other sarcomas, and similar for SEF and LGFMS.

A Practical Approach to Small Round Cell Tumors Involving the Gastrointestinal Tract and Abdomen

Small round cell neoplasms are diagnostically challenging owing to their clinical and pathologic overlap, necessitating use of large immunopanels and molecular analysis. Ewing sarcomas (ES) are the most common, but EWSR1 is translocated in several diverse neoplasms, some with round cell morphology. Molecular advances enable classification of many tumors previously termed 'atypical ES'. The current WHO Classification includes two new undifferentiated round cell sarcomas (with CIC or BCOR alterations), and a group of sarcomas in which EWSR1 partners with non-Ewing family transcription factor genes. This article reviews the spectrum of small round cell sarcomas within the gastrointestinal tract and abdomen.

Response to Immunotherapy in Sclerosing Epithelioid Fibrosarcoma: Case Report and Literature Review

Sclerosing epithelioid fibrosarcoma (SEF) is an extremely rare subtype of sarcoma that appears histologically low-grade yet usually has a clinically aggressive course with a high rate of local recurrence and distant metastasis. However, these recurrences and metastases often occur years after initial treatment. Metastases can be to the lung as well as extra-pulmonary sites. In this case report, we discuss a patient who developed SEF in the deep soft tissue with metastases. This patient underwent checkpoint inhibitor therapy, with disease response. Thus, SEF is a sarcoma subtype with a unique tumor biology, and immunotherapy may be a promising avenue for treatment.