S6343 A Rare Case of Gastric Metastasis From Recurrent Buccal Squamous Cell Carcinoma in a Patient With Severe Anemia

Introduction: While primary gastric squamous cell carcinoma (GSCC) is a rare entity, comprising less than 0.1% of gastric cancers, gastric metastases from head and neck squamous cell carcinoma (HNSCC) is exceptionally rare. Our case illustrates the uncommon occurrence of gastrointestinal (GI) metastases in a patient with recurrent buccal squamous cell carcinoma (bSCC). It highlights the importance of recognizing gastric metastasis as an atypical and aggressive pattern of HNSCC and its consideration in the evaluation of unexplained anemia in this population. Case Description/Methods: A 68-year-old man with a history of bSCC, previously treated with surgery, radiation, and chemotherapy, presented with severe symptomatic anemia. Labs showed critically low hemoglobin (3.6 g/dL). He reported dyspnea on exertion, progressive weakness, palpitations, and occasional bright red blood per rectum, which he attributed to constipation. He denied melena or hematemesis. On exam, he was pale and cachectic but hemodynamically stable, with oral findings consistent with known bSCC recurrence. Labs were negative for hemolysis, but positive guaiac stool test and persistent anemia prompted further evaluation. He required a total of 5 units of packed red blood cells, with hemoglobin stabilizing at 7.9 g/dL. Abdominal computed tomography (CT) showed no acute GI pathology. Esophagogastroduodenoscopy revealed a 3 cm ulcerated mass on the gastric anterior wall, which was biopsied and confirmed SCC involving the gastric mucosa. Discussion: Both primary and metastatic SCC of the stomach are rare. Gastric metastases from HNSCC, especially of buccal mucosa origin, is highly unusual. This type of gastric metastatic spread is unusual due to the lack of direct lymphatic or hematogenous routes. Iatrogenic seeding (e.g., percutaneous endoscopic gastrostomy tube placement) is a known mechanism, but our patient had no history. Isolated cases exist of HNSCC with aggressive and atypical metastatic patterns, including one that describes duodenal involvement, lending support to the plausibility of GI metastasis. Our patient's imaging showed no other metastases, affirming the uncommon nature of gastric-only spread. Gastric metastasis should be considered in patients with a history of HNSCC and persistent unexplained anemia. While localized PGSCC may be surgically treated, gastric metastases follow systemic HNSCC treatment protocols. Both scenarios portend a poor prognosis. Recognizing the potential for atypical presentations is critical for timely diagnosis, staging, and management of these patients.