Small-cell lung cancer with Mallory-Weiss syndrome as the prominent manifestation.

: The presence of Mallory-Weiss syndrome (MWS) in patients with small-cell lung cancer (SCLC) is uncommon. MWS is characterized by longitudinal superficial mucosal laceration at the esophagogastric junction and can be caused by a variety of causes, with upper digestive tract hemorrhage as the primary manifestation. SCLC is the most invasive histological subtype of lung cancer, and approximately a quarter of all SCLC patients undergo paraneoplastic syndrome of inappropriate antidiuretic hormone secretion, such as hyponatremia. In this study, we report a case of MWS in a middle-aged patient who was diagnosed with SCLC associated with hyponatremia. Clinicians should be alerted of the presence of MWS in upper gastrointestinal bleeding, such as epigastric pain, hematemesis, or melena, and keep SCLC in mind as a potential cause for underlying disease identification.