Supplementary Material for: Case Report: A Case of Primary Squamous Cell Carcinoma of the Small Intestine

Introduction
Primary squamous cell carcinoma (SCC) of the small intestine is an exceptionally rare malignancy, with limited cases reported in the literature. The rarity of this condition, combined with nonspecific clinical manifestations, poses significant diagnostic and therapeutic challenges.
Case Presentation
We report the case of a 47-year-old woman who presented with a two-month history of left lower abdominal pain and discomfort. Imaging studies, including enhanced abdominal CT and PET-CT, revealed a suspicious mass in the jejunum. Comprehensive diagnostic evaluations excluded metastatic origins, and a diagnosis of primary small intestinal SCC was confirmed by histopathology and immunohistochemistry. The patient underwent radical surgical resection, which revealed a poorly differentiated SCC invading the serosa and regional lymph nodes. Postoperative management included infection prevention and fluid rehydration, with recommendations for adjuvant chemotherapy and immunotherapy based on multidisciplinary consultation. Despite the advanced disease stage, the patient recovered well post-surgery and is undergoing regular follow-up.
Conclusion
This case underscores the importance of thorough diagnostic evaluation to distinguish primary SCC from metastatic lesions. Early surgical intervention is critical for improving prognosis in this rare malignancy. The findings contribute to the limited knowledge on primary SCC of the small intestine and emphasize the need for further research to guide optimal management strategies.