We present the case of a 35-year-old woman with previous hereditary retinoblastoma treated with radiotherapy, admitted due to severe iron deficiency anemia. Upper endoscopy and endoscopic ultrasound revealed a 5-cm polypoid lesion in the fundus arising from muscularis mucosa. Histological findings favored a sarcoma with muscular differentiation. After exclusion of metastatic disease, the patient underwent surgery and diagnosis of primary gastric leiomyosarcoma was confirmed. We report a case of double rarity of gastric leiomyosarcoma, as she presented with severe anaemia from a polypoid lesion of the gastric fundus.