Introduction to Low-Grade Myofibroblastic Sarcoma

Low-grade myofibroblastic sarcoma (LGMS) is an uncommon malignant tumor that primarily involves myofibroblasts. While it usually occurs in the oral cavity or extremities, its presence in the orbit is exceedingly rare. This case report discusses a 68-year-old woman presenting with progressive proptosis, illustrating the importance of comprehensive histological and molecular analysis in such cases.

Clinical Presentation and Imaging Findings

The patient presented with a painless protrusion of the left eye. Clinical examination revealed unilateral proptosis and restricted ocular motility. Furthermore, imaging with CT and MRI identified a well-defined tumor measuring 41 x 19 mm. The mass extended along the lateral rectus muscle. Consequently, clinicians performed an incisional biopsy to determine the tumor's nature. However, early symptoms of proptosis can often mimic benign conditions, making imaging an essential first step.

Histological and Molecular Characteristics of Low-Grade Myofibroblastic Sarcoma

Histological evaluation of the specimen showed a spindle cell tumor. Specifically, the cells exhibited a fascicular to storiform pattern within a myxoid stroma. Additionally, immunohistochemistry played a critical role in the differential diagnosis. The tumor tested positive for smooth muscle actin (SMA) and calponin. Conversely, it was negative for caldesmon and desmin. Therefore, the diagnosis of low-grade myofibroblastic sarcoma was considered. Notably, next-generation sequencing (NGS) later confirmed an HMGA2-NAV3 gene fusion. This finding, combined with MDM2 and CDK4 amplifications, supported the final malignant diagnosis.

Treatment and Long-Term Outcomes

The medical team managed the condition with en bloc orbital resection. Following the surgery, the patient showed no signs of recurrence after 18 months. Although LGMS has a known potential for local recurrence, complete surgical excision remains the treatment of choice. Thus, early detection and clear surgical margins are vital for improving patient outcomes in these rare orbital malignancies. Moreover, regular follow-up is necessary due to the tumor's infiltrative nature.

Frequently Asked Questions

How is orbital low-grade myofibroblastic sarcoma diagnosed?

Diagnosis requires a combination of clinical presentation, imaging (MRI/CT), and detailed histopathological examination. Specifically, immunohistochemistry and molecular testing for gene fusions like HMGA2-NAV3 are often necessary to distinguish it from other spindle cell tumors.

What is the primary treatment for LGMS?

The standard of care for low-grade myofibroblastic sarcoma is wide or en bloc surgical resection. Because these tumors are prone to local recurrence, achieving negative surgical margins is essential for long-term success.

Disclaimer: This content is for informational and educational purposes only. It does not constitute medical advice or a substitute for professional healthcare. Refer to the latest local and national guidelines for clinical practice.

References

Bendtsen AW et al. Low-grade myofibroblastic sarcoma of the orbit in a 68-year-old woman: a case report. Orbit. 2026 May 04. doi: 10.1080/01676830.2026.2668010. PMID: 42077189.

Tang L, et al. Primary low-grade myofibroblastic sarcoma: A rare case report of this tumor in the orbit and literature review. Eur J Ophthalmol. 2020 Nov 16;30(6):NP1120672120970392. doi: 10.1177/1120672120970392.

Gao G, et al. Low-grade myofibroblastic sarcoma: a case report and literature review. Medicine (Baltimore). 2017 Dec;96(50):e9172. doi: 10.1097/MD.0000000000009172.