Rare tongue base metastasis from SMARCA4-deficient undifferentiated non-small cell lung carcinoma: a case report.

SMARCA4-deficient non-small cell lung cancer (SMARCA4-dNSCLC) is a rare, aggressive subtype with a high propensity for early metastasis and poor prognosis. Common metastatic sites include the bone, brain, adrenal glands, liver, and spleen; metastasis to the base of the tongue, however, is exceptionally rare. We present a unique case of SMARCA4-dNSCLC with concurrent metastases to both the adrenal gland and the base of the tongue. A 44-year-old male presented with cough and shortness of breath. Imaging revealed a right hilar mass, a left adrenal gland mass, and a nodule at the right tongue base. Histopathological examination of biopsies from the tongue base and mediastinal lymph nodes confirmed the diagnosis of SMARCA4-deficient undifferentiated NSCLC with metastases (T3N2M1c, stage IVB). Following a multidisciplinary discussion, the patient received combination therapy with paclitaxel, cisplatin, and tislelizumab. After three cycles, a partial response (PR) was achieved. The treatment was well-tolerated without significant adverse events, and the patient's condition remained stable with no signs of recurrence. This case highlights the unusual co-occurrence of a common (adrenal) and a rare (tongue base) metastatic site in SMARCA4-dNSCLC, which posed considerable diagnostic challenges. It expands the known clinical spectrum of this malignancy and underscores the importance of recognizing its rare metastatic patterns to guide accurate diagnosis and treatment.