First Case Of Metastatic Smarca4-Deficient Nsclc Of Gingiva

SMARCA4-deficient non-small cell lung carcinoma (SMARCA4-dNSCLC) is a rare and highly aggressive malignancy characterized by the loss of SMARCA4 (BRG1) protein expression. Although metastases to many organs have been reported, metastasis to the oral cavity has not been documented. A 68-year-old male with a smoking history was admitted to the hospital due to two-month-long cough and a gingival mass persisting for one month. Clinical examination identified an irregular mass with ill-defined borders measuring 5 cm located in the left upper gingiva. Histopathological examination revealed that the tumor consisted of round to epithelioid cells, exhibiting polymorphic features with vesicular nuclei, prominent nucleoli, abundant eosinophilic cytoplasm, a high mitotic rate, and formed sheet-like structure. Multinucleated tumor cells were present. Immunohistochemical analysis showed the tumor cells were positive for CK7, negative for BRG1, exhibited a high Ki-67 proliferation index (90%). Chest computed tomography revealed a malignant mass in the right lung, accompanied by metastases present in the left lung and mediastinal lymph nodes. Pathological examination of biopsies from the right lung tumor were consistent findings. Unfortunately, the patient succumbed to respiratory failure one month after diagnosis. This case of SMARCA4-dNSCLC highlights its highly aggressive characteristics, as well as the diagnostic and therapeutic challenges, thus emphasizing the importance of comprehensive diagnostic workup. Oral pathologists should consider SMARCA4-deficient tumor in middle-aged or elderly male patients who present with poorly differentiated and highly invasive masses, given the typical negative BRG1 pathological characteristic.