A 65-year-old woman had received chemotherapy for malignant lymphoma since 2011. After the 8th course, computed tomography revealed the disappearance of lymph node metastasis, except for 22mm of the mass located on the tail side of the antrum. MRI showed a low intensity mass on the T1 and T2-weighted images. FDG-PET did not show abnormal uptake in the tumor. EUS-FNA did not reveal a definitive diagnosis. We performed a laparotomy for diagnosis and treatment. Intraoperative findings showed that the tumor occurred in the mesentery of the transverse colon. The pathological diagnosis was angiomyolipoma. The patient has been free from recurrent disease for 2 years and 6 months. Angiomyolipoma originating in the transverse mesentery region is rare and, due to various percentage of tissue factors, there are no fixed view of image findings. Furthermore, a large tissue volume is need for histological diagnosis. Laparotomy is useful for diagnosis and therapy for angiomyolipoma occurring in the mesentery of the transverse colon.