Metachronous Primary Adenocarcinoma of Lung During Adjuvant Imatinib Mesylate Therapy for Gastrointestinal Stromal Tumor of Stomach: A Case Report.

Gastrointestinal stromal tumor (GIST) is the most common mesenchymal tumor in gastrointestinal tracts; however, the synchronous or metachronous coexistence of GIST with additional primary malignancy is not common.Here, we present an unusual case of gastric GIST with metachronous primary lung adenocarcinoma diagnosed during his adjuvant treatment with oral receptor tyrosine kinase inhibitor imatinib mesylate (400 mg daily). After 6-month use of imatinib, the patient suffered from dry cough and dyspnea. Subsequent lung biopsy demonstrated adenocarcinoma with diffuse interstitial changes.Our research emphasizes the possibility of an additional primary tumor with GIST, and reminds the clinicians to strengthen the surveillance of the additional cancer during the follow-up of GIST patients.