[A CASE OF PRIMARY ADRENAL LYMPHOMA SUSPECTED AS ADRENAL METASTATIC TUMOR FROM GASTROINTESTINAL STROMAL TUMOR].

We present a case of 75 year's old man for whom small bowel resection was performed for a small intestinal tumor diagnosed as a gastrointestinal stromal tumor (GIST) with KIT exon 11 mutation and intermediate Miettinen risk. Computed tomography (CT) 18 months after surgery showed a right adrenal mass measuring 20 mm in size. Imatinib therapy couldn't show the tumor shrinkage, and the adrenal mass increased up to 37 mm in size 3 months later. He was referred to our department for further examination and treatment. We diagnosed this adrenal tumor as imatinib resistant GIST or adrenal primary malignancy and performed retroperitoneal laparoscopic right adrenalectomy. The pathological diagnosis was diffuse large B-cell lymphoma (DLBCL) not GIST and PET-CT revealed systemic metastasis of DLBCL one month later after surgery. Six courses of R-CHOP therapy achieved a complete response.