SMARCA4-deficient non-small cell lung cancer with metastasis to the sigmoid colon: a case report.

Background: SWI/SNF-related, matrix-associated, actin-dependent regulator of chromatin, subfamily a, member 4-deficient non-small cell lung cancer (SMARCA4-dNSCLC) is a rare subtype of NSCLC whose definitive radiographic characteristics have not yet been fully delineated. Clinically, these tumors often metastasize to distant organs and lymph nodes at an early stage, which is strongly associated with poor clinical prognosis. The common metastatic sites include bone, brain, adrenal glands, liver, and spleen, whereas intestinal metastasis is extremely rare. In this case, we describe a rare instance of SMARCA4-deficient NSCLC with metastasis to the sigmoid colon.

Case description: A 59-year-old male presented with hoarseness and shortness of breath. Computed tomography (CT) imaging revealed an irregular mass in the posterior apical segment of the upper lobe of the left lung, with enlarged lymph nodes in the mediastinum and left lung hilum. A biopsy of the lung mass confirmed the diagnosis of NSCLC with SMARCA4 gene deletion. CT also revealed uneven thickening of the sigmoid colon wall, which was proved to be metastases from the lung cancer through surgical pathology. The patient initially underwent chemotherapy combined with immunotherapy and intensity-modulated radiotherapy for the lungs. However, a follow-up CT revealed progression in the sigmoid colon tumor. Consequently, the patient underwent laparoscopic radical sigmoid colectomy with regional lymph node dissection. Two months postoperatively, metastasis to the left adrenal gland was detected. The treatment regimen was adjusted to a combination therapy consisting of gemcitabine, nedaplatin, bevacizumab, and camrelizumab accordingly. The patient demonstrated a favorable response to this treatment, with no evidence of recurrence or further metastasis to date.

Conclusions: This case represents the first reported instance of SMARCA4-dNSCLC with metastasis to the sigmoid colon. The atypical clinical and radiological features of this condition pose significant diagnostic challenges, particularly in differentiating metastatic lesions from primary colonic tumors. This case underscores the significance of recognizing rare metastatic patterns in SMARCA4-dNSCLC, enriching the literature on its diverse manifestations and providing a critical reference for clinicians in diagnosing and managing SMARCA4-dNSCLC with sigmoid colon metastasis.