Case Report: Primary epithelioid sarcoma of orbit: first case in Asia and literature review

Epithelioid sarcoma is an exceedingly rare malignant soft tissue neoplasm with unclear histogenesis and distinctive epithelioid morphology. Primary epithelioid sarcoma of orbit represents an extremely rare clinical entity, with only isolated case reports documented globally. Notably, no formal, peer-reviewed case report of primary epithelioid sarcoma of orbit has been published in Asia to date.

A 25-year-old male patient presented with slowly progressive, painless proptosis of the left eye. Orbital MRI revealed an irregular mass in the superomedial extraconal space of the left orbit, with an initial radiological impression of vascular tumor or inflammatory lesion. Histologically, the tumor displayed characteristic multinodular growth, composed of a mixture of epithelioid and spindle cells with necrotizing granuloma-like changes. Skeletal muscle invasion and vascular tumor emboli were observed. Immunohistochemically, tumor cells co-expressed epithelial markers (broad-spectrum CK, EMA), mesenchymal marker (Vimentin) and CD34, with loss of nuclear INI1 (SMARCB1) expression. Whole-body PET-CT performed postoperatively excluded distant metastasis, and a diagnosis of classic primary epithelioid sarcoma of the left orbit was confirmed. The patient underwent extended tumor resection combined with local intensity-modulated radiotherapy. No local recurrence or distant metastasis was detected at 7 months postoperatively.

Primary epithelioid sarcoma of the orbit is diagnostically challenging, and pathological examination remains the gold standard for diagnosis. The combination of characteristic histological features and a distinct immunophenotype (loss of INI1) is critical for definitive diagnosis and differential diagnosis. We report the first case of primary epithelioid sarcoma of orbit in Asia, which enriches the clinicopathological data of this rare tumor in the Asian population and provides a key reference for its clinical management and pathological diagnosis. However, as a single-case study, larger series are needed to confirm generalizability.