Peritoneal Carcinomatosis as an Initial Presentation of Gastrointestinal Stromal Tumor: A Case Report and Review of the Literature.

Gastrointestinal stromal tumors (GISTs) are a rare type of tumor with a high risk of malignant transformation. The majority of GISTs are asymptomatic. Surgical resection remains the mainstay of treatment given that GIST is resistant to traditional chemotherapy and radiotherapy. In the last two decades, the discovery of targeted therapy with tyrosine kinase inhibitor therapy (TKI) and widespread mutation analysis of tumors have transformed the treatment of GIST. We present a case of a patient in whom imaging findings were consistent with carcinomatous peritonitis concerning a gynecological malignancy but who was later found to have an unresectable GIST which locally regressed with TKI.