Clinical Report: Uncommon Thoracic SMARCA4-Deficient Tumor with Metastasis

Overview

This case study presents a 60-year-old man with a thoracic SMARCA4-deficient undifferentiated tumor (SMARCA4-UT) that metastasized to the extraocular muscles, causing diplopia.

Background

Thoracic SMARCA4-deficient undifferentiated tumors are highly aggressive malignancies with a propensity for early metastasis, often presenting with local invasion. The involvement of extraocular muscles is rare.

Data Highlights

No numerical data or trial data available in the article.

Key Findings

• The patient presented with binocular diplopia and ocular pain, with imaging revealing a nodular lesion in the left inferior rectus muscle.
• Immunohistochemistry confirmed the diagnosis of SMARCA4-UT with complete loss of BRG1 expression and a high Ki-67 index.
• Systemic evaluation identified a primary lung lesion with mediastinal lymphadenopathy and adrenal gland involvement.
• The patient died shortly after one cycle of chemotherapy and immunotherapy.
• This case is the first documented instance of thoracic SMARCA4-UT presenting as an isolated metastasis to the inferior rectus muscle.

Clinical Implications

Early tissue diagnosis is important when symptoms do not respond to initial treatment.

Conclusion

This case represents the first reported instance of thoracic SMARCA4-UT presenting as an isolated metastasis to the inferior rectus muscle.

Related Resources & Content

1. Le Loarer et al., WHO Classification of Thoracic Tumors, 2021 -- SMARCA4-deficient undifferentiated tumors
2. Frontiers in Oncology, 2026 -- Case Report: Synaptophysin-positive SMARCA4-deficient undifferentiated thoracic tumour
3. Frontiers in Oncology, 2026 -- CT imaging features of pulmonary SMARCA4-deficient undifferentiated carcinoma
4. Ophthalmology Management, 2018 -- Multiple myeloma and abducens palsy
5. Academic.oup.com, 2026 -- First-line platinum-based chemo-immunotherapy for SMARCA4-UT
6. Retinal Physician — Ocular Tumor Masquerade Syndromes
7. The 2021 WHO Classification of Lung Tumors: Impact of Advances Since 2015 - ScienceDirect
8. https://academic.oup.com/oncolo/article/30/9/oyaf266/8240849