S6277 A Rare Co-Occurrence of Squamous Cell Carcinoma of the Stomach and Gastroesophageal Junction With Positive Immunohistochemistry: Primary or Metastatic?

Introduction: Primary gastric squamous cell carcinoma (GSCC) is an extremely rare malignancy with unclear standards of care due to a typically late diagnosis and poor prognosis. While GSCC are uncommon, esophageal cancers are more prevalently of squamous cell type. With few reported cases in literature, the co-occurrence of GSCC and esophageal squamous cell cancers (ESCC), diagnosis, targeted therapies, and prognosis remain to be fully understood. Case Description/Methods: A 51-year-old man with a 35-year active smoking history presented to the ED with dysphagia, odynophagia to solids and liquids, epigastric pain, nausea and vomiting. He denied fever, alcohol use and weight loss. Clinical findings of epigastric tenderness and iron deficiency anemia were present. Computed tomography (CT) abdomen showed a distal esophageal and gastric fundus thickening. An urgent esophagogastroduodenoscopy (EGD) revealed LA Grade D esophagitis, narrowing of the distal esophageal lumen with marked cardia edema and inflammation. He was started on a proton pump inhibitor with a plan to return in 4 weeks for a repeat when inflammatory changes and risk for perforation would have diminished. Six weeks later, he returned cachectic with progressive worsening of prior symptoms. Repeat CT abdomen showed a distal esophageal thickening, gastric fundus mass (5.4 × 4.0 × 4.6 cm) and no lymphadenopathy. EGD demonstrated LA Grade B distal esophagitis, a gastroesophageal (GEJ) mass and a large ulcerated non-bleeding gastric cardia mass. Histology confirmed a moderately differentiated squamous cell carcinoma, inactive gastritis and intestinal metaplasia. Immunohistochemistry (IHC) was p40 positive and negative for PD-L1, mucicarmine and H. pylori. A multidisciplinary team opted for positron emission tomography/CT staging and neoadjuvant chemoradiotherapy. He then received a feeding jejunostomy tube with partial esophagogastrectomy. Discussion: As in this unique case, a clinical dilemma arises when SCC appears synchronously in the GEJ and stomach. Although a primary GSCC in the cardia less likely presents with an ESCC, this event is not absolutely discounted. While ESCC is more common overall, it is less frequent at the GEJ compared to adenocarcinomas. IHC confirmed both tumors to be primary SCC but could not determine if they were either synchronous, a primary GSCC with extension to the GEJ or vice versa. While primary GSCC and ESCC follow established protocols for other squamous cell cancers, further investigation of this rare clinical entity may improve early diagnosis and ultimately, therapeutic best practices.