A 66-year-old non-human immunodeficiency virus (HIV) woman was admitted with recurrent moderate cramp-like abdominal pain, nonbloody diarrhea, periodic nausea, and fatigue. Her medical history included terminal ileitis since 2 years. She had no unhealthy habits and her medication history included mesalazine and methylprednisolone (9 mg daily) for the past 4 months with improved symptoms. Physical examination revealed no skin rash, mild epigastric tenderness on abdominal palpation, and nonpalpable liver and spleen. Laboratory findings disclosed mild anemia and increased levels of fecal calprotectin and C-reactive protein. HIV-1,2 Western blots were negative. Abdominal ultrasonography and contrast-enhanced computed tomography showed unremarkable findings. Upper gastrointestinal endoscopy revealed atrophy and a reddish, round, and elevated maculopapular lesion with friability in the stomach body (Fig. 1A). Mucosal nodularity with no abnormal capillary vessels was observed throughout the gastric antrum (Fig. 1B). Intramucosal ruptures and hemorrhage without any perforation signs had happened after biopsy (Fig. 1C). She was treated with hemostatic agents and showed positive effects. Helicobacter pylori were not detected. Histopathology demonstrated spindle-cell proliferation in the submucosa (Fig. 2A), emphasized by immunochemistry for CD31 (Fig. 2B) and positivity to human herpesvirus 8 (Fig. 2C). Deposition of > 10-μm thick collagen bands was observed in the subepithelial layer, and the specimen was positive for Masson’s trichrome staining (Fig. 2D). Colonoscopy and small bowel capsule endoscopy were unremarkable. Histopathology of the colon showed that chronic inflammatory cells had infiltrated in the subepithelial layer with collagen deposition. She was diagnosed with isolated gastric Kaposi’s sarcoma, coexisting collagenous gastritis, and microscopic colitis. Treatment with budesonide, esomeprazole, pegylated liposomal doxorubicin was prescribed.