Peritoneal Carcinomatosis in an Adult With Sjögren's Syndrome: A Diagnostic Dilemma Revealing a Rare Association With Primary Gastric Adenocarcinoma

Sjögren's syndrome (SS) is a systemic autoimmune disease that mainly affects middle-aged women. It is rarely associated with solid neoplasms. We report a 60-year-old woman with a past medical history relevant for SS who was diagnosed with advanced-stage gastric adenocarcinoma upon evaluating for peritoneal carcinomatosis and succumbed two months after her original diagnosis. This case highlights the significance of considering gastrointestinal (GI) malignancy as an essential differential, particularly when evaluating patients with SS who fail conservative treatment for their GI symptoms.