Background: Leiomyosarcomas of the stomach are very rare. At the time of primary diagnosis the tumors are most often in advanced stage and the patients complain of abdominal pain due to large tumor size. Endosonographically, the tumors impress as submucous mass with suspicion to malignancy. Sarcomas following hereditary retinoblastoma in childhood are in generally located in the soft tissue. Structural alterations of the retinoblastoma gene (RB1) seem to be involved in the pathogenesis.

Methods: A 37-year-old german male suffered from reflux disorder. In endoscopic examination a small polypous tumor was detected in the stomach. The resection specimen revealed an intramucosal leiomyosarcoma. At the age of one year, the patient had a retinoblastoma.

Conclusions: This is the unique report of an intramucosal gastric leiomyosarcoma and the first account of a gastric leiomyosarcoma after retinoblastoma in childhood. A careful clinical follow-up is advised because of increased risk of developing further metachronous malignancies.