constituting about 1% of all colorectal malignancies [1], 8% of all appendiceal tumors and 0.3-0.7% of all appendectomy specimens [2]. Preoperative diagnosis of LAMN is difficult due to rarity of the disease and the absence of characteristic clinical symptoms [3]. And then, laboratory tests are not specific in patients with LAMN. Surgical resection is the first choice for LAMN, and a chemotherapy has not yet been established [5]. Recently, the laparoscopic surgery is increasing; however, surgical approach and lymph node (LN) dissection are still controversial because of the difficulty of preoperative malignancy diagnosis and the risk of intraoperative injury of the mucinous tumor [6]. We present a case of LAMN with difficulties in making the preoperative diagnosis that exhibited invagination, and was treated by laparoscopy-assisted ileocecal resection. Case report The patient was a 40-year-old female, who had a gradually increasing pain in right lower quadrant with nausea and vomiting. Her body temperature was 37.3 °C and her abdomen was soft, but palpable mass was present in the hypogastric region with tenderness. In the laboratory tests, carbohydrate antigen 125 and carcinoembryonic antigen (CEA) levels were elevated to 54 U/ml and 7.7 ng/ml, respectively. Computed tomography (CT) showed a concentric circles containing cystic structure with calcification at the left side of the lesion (Fig. 1a, b). We diagnosed the invagination of intestine and an emergency laparoscopic examination was performed; nevertheless intestinal tract showed no abnormal finding. After laparoscopic examination, the abdominal pain persisted. Total colonoscopy revealed a 5-cm Abstract Low-grade appendiceal mucinous neoplasm (LAMN) is rare disease, and the absence of characteristic clinical symptoms makes preoperative diagnosis difficult. The strategy of treatment for LAMN has not been established. Surgical approach and lymph node (LN) dissection are still controversial. We herein present a case of LAMN with difficulties in making the preoperative diagnosis, which exhibited invagination and was treated by laparoscopy-assisted ileocecal resection with LN dissection. When cystic mass is detected in the bowel, LAMN or mucinous adenocarcinoma should be considered as a different diagnosis. And the laparoscopy-assisted ileocecal resection is a feasible operation for LAMN with careful procedure.