S6411 Primary Gastric Squamous Cell Carcinoma: A Rare Case Highlighting the Need for an Early Diagnosis

Introduction: Primary gastric squamous cell carcinoma (PGSCC) is an exceptionally rare malignancy. Since its first description in 1895, fewer than 100 cases have been reported, comprising 0.04%–0.07% of all gastric cancers. Its pathogenesis remains unclear, and treatment strategies are not standardized. The disease carries a poor prognosis, with a median survival of 7 months. Case Description/Methods: A 71-year-old Navajo man with a 50+ pack-year smoking history presented with 8 weeks of abdominal pain and intermittent hematemesis. He reported a 1-year history of reduced appetite and unintentional weight loss of 30 lbs. Exam was unremarkable. Labs revealed microcytic iron-deficiency anemia (hemoglobin 9.3 g/dL, mean corpuscular volume 77 fL). He noted that a prior computed tomography (CT) scan performed at an outside hospital 6 months earlier had shown gastric ulceration suspicious for malignancy, but he was lost to follow-up. esophagogastroduodenoscopy (EGD) revealed a 4 cm fungating, centrally ulcerated mass involving the cardia, fundus, and proximal body. Biopsy confirmed invasive squamous cell carcinoma. Immunohistochemistry showed strong p63 positivity and patchy CK7 expression, consistent with squamous differentiation. HER2 was negative, and H. pylori was not detected. Endoscopic ultrasound demonstrated a hypoechoic mass along the lesser curvature with sonographic evidence of serosal invasion and peri-gastric lymphadenopathy. Per endosonographic criteria, the tumor was staged at least T3N1Mx (T4 could not be excluded). No distant metastases were identified on CT scan. Despite good performance status (ECOG 0), the patient had an aggressive disease course and died at home within 8 weeks of diagnosis before treatment could be initiated. Discussion: This case exemplifies the typical clinical presentation of rare PGSCC. Although epidemiologic data are scarce, PGSCC predominantly affects men over 60 years of age and is more prevalent among African Americans. In addition, patients tend to be in advanced stages of disease compared to gastric adenocarcinoma. Due to its rarity, no standardized treatment guidelines exist. Surgical resection (total gastrectomy with D2 lymphadenectomy) is the reported treatment. Use of adjuvant chemotherapy and radiotherapy varies widely in literature. Given PGSCC’s poor prognosis, early endoscopy with tissue sampling, multidisciplinary care, and proactive patient engagement are critical to improving outcomes. In underserved demographics such as the one our patient belongs to, limited access to care and delayed follow-ups exacerbate diagnostic delays.