The first case of BRG (SMARCA4)/INI Deficient Tracheal Carcinoma: A Case Report and Review of the Literature

Abstract

Abstract Introduction/Objective Primary tumors of the trachea are rare, they account for less than 0.1% of tumors in humans. In adults, 90% of primary tracheal tumors are malignant, with squamous cell carcinoma and adenoid cystic carcinoma accounting for two-thirds, with other forms occurring less frequently. The BRG (SMARCA4)/INI deficient tumor is a relatively new defined entity which is recently introduced in the WHO Classification of Tumors, 5th edition, 2021. The gene SMARCA4 is located at 19p13. Loss of SMARCA4 has been reported in several aggressive tumors with high- grade undifferentiated rhabdoid morphology but has not been reported in the trachea. Hence, we report the first case of BRG (SMARCA4)/ INI deficient tracheal carcinoma. Methods/Case Report We present a 60-year-old male with a history of tobacco abuse, shortness of breath, and a tracheal mass on chest imaging. Bronchoscopy was performed and showed a fleshy friable lesion at the anterior trachea with evidence of blood dripping into the distal airways. Results (if a Case Study enter NA) Microscopic examination showed a high grade, poorly differentiated carcinoma with tumor necrosis, high mitotic counts, and marked nuclear pleomorphism. Immunohistochemical stains were performed. The tumor cells were strongly and diffusely positive for CK-7 and weakly positive for synaptophysin, negative for pan-cytokeratin, TTF-1, CK-20, p40, CK5/6, and chromogranin. Then BRG (SMARCA4) and INI 1 (BAR47) were performed and showed negative staining on BRG expression, while INI 1 is intact (nuclear expression). These features are consistent with BRG (SMARCA4)/ INI deficient carcinoma. Conclusion BRG (SMARCA4)/ INI deficient carcinoma is a new entity in the trachea, which is very aggressive with a poor prognosis. Targeted therapy or clinical trials may be available as additional cases are diagnosed in the future.