Predictive factors associated with anastomotic leakage after resection of rectal cancer: a multicenter study with the Hiroshima Surgical study group of Clinical Oncology.

PURPOSE: Several factors have been reported as risk factors for anastomotic leakage after resection of rectal cancer. This study aimed to evaluate the risk factors for anastomotic leakage, including nutritional and immunological indices, following rectal cancer resection. METHODS: This study used a multicenter database of 803 patients from the Hiroshima Surgical study group of Clinical Oncology who underwent rectal resection with stapled anastomosis for rectal cancer between October 2016 and April 2020. RESULTS: In total, 64 patients (8.0%) developed postoperative anastomotic leakage. Five factors were significantly associated with the development of anastomotic leakage after rectal cancer resection with stapled anastomosis: male sex, diabetes mellitus, C-reactive protein/albumin ratio ≥ 0.07, prognostic nutritional index < 40, and low anastomosis under peritoneal reflection. The incidence of anastomotic leakage was correlated with the number of risk factors. The novel predictive formula based on odds ratios in the multivariate analysis was useful for identifying patients at high risk for anastomotic leakage. Diverting ileostomy reduced the ratio of anastomotic leakage ≥ grade III after rectal cancer resection. CONCLUSIONS: Male sex, diabetes mellitus, C-reactive protein/albumin ratio ≥ 0.07, prognostic nutritional index < 40, and low anastomosis under peritoneal reflection are possible risk factors for developing anastomotic leakage after rectal cancer resection with the stapled anastomosis. Patients at high risk of anastomotic leakage should be assessed for the potential benefits of diverting stoma.

[A Case of Unresectable Pancreatic Cancer with Massive Cancerous Ascites Responsive to KM-CART].

A 79-year-old woman visited our hospital complaining of bloating. An abdominal enhanced CT scan revealed pancreatic body cancer with cancerous ascites and multiple liver metastases. We started gemcitabine(GEM)plus nab-paclitaxel chemotherapy. Chemotherapy was not continued because she was unable to take oral medication owing to increased cancerous ascites. We conducted modified KM-cell-free and concentrated ascites reinfusion therapy(KM-CART). Her symptoms improved, and she began having oral intake after KM-CART. Chemotherapy was then re-initiated. Seven months have now passed since we started chemotherapy, and we can continue chemotherapy while conducting KM-CART repeatedly. KM- CART is useful for treating unresectable pancreatic cancer with massive cancerous ascites in terms of continuing chemotherapy.

Multicenter phase II study of biweekly CAPIRI plus bevacizumab as second-line therapy in patients with metastatic colorectal cancer (JSWOG-C3 study).

BACKGROUND: Triweekly capecitabine plus irinotecan (CAPIRI) was not a replacement for fluorouracil, leucovorin, and irinotecan (FOLFIRI) in the treatment of metastatic colorectal cancer (mCRC) because of the potential for greater toxicity. Recently, it has reported that mCAPIRI is well tolerated and non-inferior to FOLFIRI. In this study, we conducted a multicenter phase II trial to assess the efficacy and safety of biweekly CAPIRI plus bevacizumab as second-line chemotherapy for mCRC with reduced toxicity and preserved efficacy. METHODS: Patients with mCRC who had received prior chemotherapy, including oxaliplatin-based regimens, were eligible for this study. The treatment protocol administered capecitabine at 1000 mg/m2 twice daily from the evening of day 1 to the morning of day 8, intravenous irinotecan at 150 mg/m2 on day 1, and bevacizumab at 10 mg/kg on day 1 every 2 weeks. Primary endpoints for this study were progression-free survival (PFS) and safety. Secondary endpoints were overall survival (OS), time to treatment failure, response rate (RR), and disease control rate (DCR). RESULTS: Fifty-one patients were enrolled in this study. Median PFS was 5.5 months [95% confidence interval (CI) 4.23-7.40 months], and median OS was 13.5 months (95% CI 11.57-20.23 months). The RR was 14.6% (95% CI 6.5-28.4%), and the DCR was 66.7% (95% CI 51.5-79.2%). Hypertension was the most common Grade 3 adverse event (27.5%), followed by neutropenia (17.6%). Only two patients suffered from grade 3 hand-foot syndrome. CONCLUSIONS: In mCRC patients, biweekly CAPIRI + bevacizumab appears effective and feasible as a second-line chemotherapy with relatively low toxicities, and has potential as a useful substitute for FOLFIRI + bevacizumab.

Spontaneous regression of transverse colon cancer with high-frequency microsatellite instability: a case report and literature review.

BACKGROUND: Spontaneous regression (SR) of colorectal cancer (CRC) is extremely rare, and only few cases have been reported. Although it is not yet clarified, a plausible mechanism for SR of CRC is an immunological event. CASE PRESENTATION: In this report, we present the case of SR of primary CRC in a 78-year-old man. Preoperative colonoscopy was performed, and a type 2 tumor measuring 30 mm in diameter in the transverse colon was detected. The biopsy revealed a poorly differentiated adenocarcinoma. Colectomy was performed 2 months after initial colonoscopy. During the surgery, only a 10-mm ulcer harboring a polypoid lesion measuring 8.5 mm was detected in the resected tissue; no other masses or carcinoma cells were seen on histological examination. Afterwards, the biopsy specimens were reanalyzed, and immunohistological analysis verified this as adenocarcinoma with stroma-infiltrating lymphocytes. Further analysis revealed a loss of two mismatch repair proteins, suggesting sporadic high-frequency microsatellite instability (MSI-H). CONCLUSION: According to previous literature, a common site of SR in CRC is the proximal colon, which is a feature of MSI-H CRC. However, our report showed a rare case of SR of CRC, which was in the transverse colon, with MSI-H present. This report indicates a relationship between immunological features of MSI-H and the occurrence of SR of CRC. A better understanding of this phenomenon and the mechanisms involved will have significant preventive and therapeutic implications for CRC, including anti-PD-1 immune checkpoint inhibitor therapy.

Cytoplasmic Hu-Antigen R (HuR) Expression is Associated with Poor Survival in Patients with Surgically Resected Cholangiocarcinoma Treated with Adjuvant Gemcitabine-Based Chemotherapy.

BACKGROUND: Hu-antigen R (HuR) is an RNA-binding protein that regulates the stability, translation, and nucleus-to-cytoplasm translocation of messenger RNAs (mRNAs). OBJECTIVE: The aim of this study was to investigate the prognostic significance of HuR in cholangiocarcinoma patients who received adjuvant gemcitabine-based chemotherapy (AGC) after surgical resection. METHODS: Nuclear and cytoplasmic HuR expression was investigated immunohistochemically in 131 patients with resected cholangiocarcinoma, including 91 patients administered AGC and 40 patients who did not receive adjuvant chemotherapy. The correlation between HuR expression and survival was evaluated by statistical analysis. RESULTS: High nuclear and cytoplasmic HuR expression was observed in 67 (51%) and 45 (34%) patients, respectively. Cytoplasmic HuR expression was significantly associated with lymph node metastasis (p < 0.01), while high cytoplasmic HuR expression was significantly associated with poor disease-free survival [DFS] (p = 0.03) and overall survival [OS] (p = 0.001) in the 91 patients who received AGC, but not in the 40 patients who did not receive AGC (DFS p = 0.17; OS p = 0.07). In the multivariate analysis of patients who received AGC, high cytoplasmic HuR expression was an independent predictor of poor DFS (hazard ratio [HR] 1.77; p = 0.04) and OS (HR 2.09; p = 0.02). Nuclear HuR expression did not affect the survival of enrolled patients. CONCLUSIONS: High cytoplasmic HuR expression was closely associated with the efficacy of AGC in patients with cholangiocarcinoma. The current findings warrant further investigations to optimize adjuvant chemotherapy regimens for resectable cholangiocarcinoma.

[A case of lung cancer with small intestine metastasis with perforative peritonitis as the initial symptom].

Herein, we report a case oflung cancer with metastasis to the small intestine, with perforative peritonitis as the initial symptom. An 82-year-old man who had undergone subtotal gastrectomy and Roux-en-Y anastomosis for gastric cancer 8 years previously was admitted to our hospital with abdominal pain. We diagnosed the patient with gastrointestinal perforation, and a chest computed tomography(CT)scan showed a mass in the right lung. A laparotomy revealed a 4×3 cm sized intestinal tumor and intestinal perforation in the immediate vicinity ofthe anastomotic site. Segmentectomy ofthe small intestine was performed. Histological examination indicated that the tumor specimen was squamous cell carcinoma. Four months later, an abdominal CT scan showed multiple liver metastases, and the patient died 6 months after the operation because ofcachexia. At autopsy, a diagnosis ofsmall intestine metastatic tumor originating from squamous cell carcinoma of the lung was made. Although small intestine metastasis from lung cancer is rare, it should be considered when progressive abdominal symptoms are observed.

A case of pancreatic adenosquamous cell carcinoma with a pseudocyst following curative surgery.

BACKGROUND: Pancreatic adenosquamous cell carcinoma (PASC) is a relatively rare histological type of pancreatic malignancy, and preoperative diagnosis is difficult because of its rarity. PASC accounts for 1-4% of all pancreatic cancers, and even after curative surgery, its prognosis is poorer than that of ordinary pancreatic adenocarcinoma. Pathologically, it shows glandular and squamous differentiation of cells. Complete resection is the only method to achieve a good long-term prognosis, and an increasing doubling time of PASC is considered to indicate early recurrence after surgery. Here, we report a rare case of PASC with an infected pancreatic cyst that was difficult to treat, along with a review of the literature. CASE PRESENTATION: A woman in her 80s with a history of breast cancer presented with pericardial pain. Computed tomography revealed a 20-mm hypovascular tumor in the body of the pancreas and a 27-mm pseudocyst. Endoscopic retrograde cholangiopancreatography showed a severe main pancreatic duct stenosis in the body of the pancreas that made cannulation impossible, and contrast media extravasation was due to pancreatic duct disruption in the pancreatic tail. Endoscopic fine-needle aspiration revealed that the tumor was a PASC. Because the patient had an infected pancreatic cyst, central intravenous nutrition and antibiotics were administered, which stabilized her general condition. She was diagnosed with resectable PASC and underwent distal pancreatectomy with lymphadenectomy. The postoperative course was uneventful. Immunohistochemical analysis of the resected specimen confirmed T2N0M0 stage IB. Systemic adjuvant chemotherapy with S-1 is ongoing. CONCLUSION: Appropriate preoperative management and preoperative accurate staging (T2N0M0 stage IB) of PASC with curative surgery can ensure predictable outcomes.

Safe suprapancreatic lymph node dissection for gastric cancer with ectopic common hepatic artery.

Suprapancreatic lymph node dissection for patients with gastric cancer in whom the common hepatic artery is located neither at the suprapancreatic margin nor in front of the portal vein is a more difficult procedure than when the common hepatic artery is in a more typical position. There is an increased risk of injury to the vessels that need to be preserved and inadequate lymph node dissection. Measures that have been reported for use in this situation are preoperative diagnosis with three-dimensional computed tomography angiography, dissection using the portal vain as a guide, and safe exposure of the portal vein with dissection to preserve the nerves at the suprapancreatic margin and in front of the portal vein. We review the literature and report our experience with a patient whose common hepatic artery was not located in the suprapancreatic margin who safely underwent suprapancreatic lymph node dissection using these methods.

[A case of advanced gastric cancer effectively treated with weekly paclitaxel as neoadjuvant chemotherapy].

We report a patient with advanced gastric cancer responding remarkably to neoadjuvant chemotherapy consisting of weekly paclitaxel. The patient was a 50-year-old male who had large advanced gastric cancer, suspected of invasion to the duodenum and pancreas and severe lymph node metastasis [cT4 (pancreas), cN2, cH0, cP0, cM0, cStage IV]. He was treated with weekly paclitaxel as neoadjuvant chemotherapy. According to gastroscope and CT findings, a significant tumor reduction was obtained after 3 courses. Therefore, distal gastrectomy with D2 nodal dissection were performed. The histological diagnosis was pT2, pN2, pStage IIIA, and the histological effect of the main tumor was judged to be Grade 2. The patient has now been in good health without recurrence for 3 years after surgery. This case suggests that neoadjuvant chemotherapy with weekly paclitaxel is a potentially effective regimen for advanced gastric cancer.

Pathological complete response of multiple liver metastases from colon cancer successfully treated with conversion surgery: A case report.

INTRODUCTION AND IMPORTANCE: Recently, the successful long-term survival of patients with unresectable distant metastases from colorectal cancer, who underwent conversion surgery after systemic chemotherapy, have been documented. Herein, we present a patient afflicted with ascending colon cancer and multiple unresectable liver metastases, who underwent conversion surgery, resulting in the complete disappearance of the pathological liver metastases. PRESENTATION OF CASE: A 70-year-old woman visited our hospital with a chief complaint of weight loss. A diagnosis of ascending colon cancer (cT4aN2aM1a [H3]: TNM classification 8th edition) stage IVa with RAS/BRAF wild-type mutation was made (four liver metastases up to 60 mm in diameter were observed in both lobes). After 2 years and 3 months of systemic chemotherapy (capecitabine, oxaliplatin, and bevacizumab), the tumor marker levels had decreased to normal ranges and all liver metastases showed partial responses with remarkable shrinkage. After confirmation of a liver function and a preserved future liver remnant volume, the patient finally underwent hepatectomy, involving partial resection of S4 and subsegmentectomy of S8, along with a right hemicolectomy. Histopathologic examination revealed that all liver metastases had completely disappeared, while regional lymph node metastases had changed into scar tissue. However, the primary tumor failed to respond to chemotherapy, resulting in ypT3N0M0 ypStage IIA. The patient was discharged from the hospital on the 8th postoperative day without any postoperative complications. She is currently on the 6th month of follow-up without any recurring metastasis. CLINICAL DISCUSSION: Curative surgery is recommended for resectable liver metastases of colorectal cancer (CRLM), be it synchronous or heterochronous. Up until now, the efficacy of perioperative chemotherapy for CRLM is limited. Chemotherapy has a double-edged aspect, where some cases have shown successful improvement in the treatment stage. CONCLUSION: To obtain the maximum benefit from conversion surgery, it is critical to incorporate the appropriate surgical technique, at the correct stage, in order avoid the progression to chemotherapy-associated steatohepatitis (CASH) in the patient.

Intracystic papillary neoplasm diagnosis following an extended cholecystectomy: a case report and literature review.

We report a case of intracystic papillary neoplasms (ICPN) that was difficult to differentiate from adenocarcinoma of the gallbladder. A 64-year-old man visited our hospital for an examination of gallbladder tumors. At the preoperative examination, the tumor was revealed a papillary type of tumor in the body of the gallbladder without the findings that without the findings that suggested the tumor invasion into the deep subserosal layer. The patient underwent an extended cholecystectomy. Papillary lesions were observed mainly in the body of the gallbladder, with flattened elevated lesions at the gallbladder fundus. Within each of these tumors, cells corresponding to intraepithelial adenocarcinoma were irregularly interspersed, leading to a diagnosis of ICPN. The patient is currently undergoing follow-up with no recurrence postoperatively. The prognosis of ICPN is generally good; however, preoperative diagnosis remains challenging. Therefore, a treatment plan for gallbladder cancer should be applied.

Current status of gastrectomy and reconstruction types for patients with proximal gastric cancer in Japan.

BACKGROUND: Surgical procedures for proximal gastric cancer remain a highly debated topic. Total gastrectomy (TG) is widely accepted as a standard radical surgery. However, subtotal esophagectomy, proximal gastrectomy (PG) or even subtotal gastrectomy, when a small upper portion of the stomach can technically be preserved, are alternatives in current clinical practice. METHODS: Using a cohort of the PGSAS NEXT trial, consisting of 1909 patients responding to a questionnaire sent to 70 institutions between July 2018 and December 2019, gastrectomy type, reconstruction method, and furthermore the remnant stomach size and the anti-reflux procedures for PG were evaluated. RESULTS: TG was the procedure most commonly performed (63.0%), followed by PG (33.4%). Roux-en-Y was preferentially employed following TG irrespective of esophageal tumor invasion, while jejunal pouch was adopted in 8.5% of cases with an abdominal esophageal stump. Esophagogastrostomy was most commonly selected after PG, followed by the double-tract method. The former was preferentially employed for larger remnant stomachs (≧3/4), while being used slightly less often for tumors with as compared to those without esophageal invasion in cases with a remnant stomach 2/3 the size of the original stomach. Application of the double-tract method gradually increased as the remnant stomach size decreased. Anti-reflux procedures following esophagogastrostomy varied markedly. CONCLUSIONS: TG is the mainstream and PG remains an alternative in current Japanese clinical practice for proximal gastric cancer. Remnant stomach size and esophageal stump location appear to influence the choice of reconstruction method following PG.

Intrahepatic cholangiocarcinoma with extensive intraductal extension of high-grade biliary intraepithelial neoplasia: a case report.

BACKGROUND: Intrahepatic cholangiocarcinoma (ICC) is frequently associated with precursor lesions, and biliary intraepithelial neoplasia (BilIN) may play a significant role in the development of ICC. However, the exact sequence and progression of these lesions remain to be elucidated. We report a rare case of ICC that exhibited extensive longitudinal intraductal extension of high-grade BilIN in the posterior bile ducts and involved the hepatic hilum and the peripheral hepatic parenchyma. CASE PRESENTATION: A 70-year-old female presented with anorexia. Computed tomography (CT) revealed a 15 mm enhancing intrahepatic tumor extending to the right intrahepatic secondary confluence. This was associated with a 7 mm diameter cystic dilatation of the segment 6 bile duct (B6). Endoscopic retrograde cholangiopancreatography (ERCP) revealed stenosis at the bifurcation of the posterior bile duct branch. Bile cytology confirmed the diagnosis of adenocarcinoma cells. Therefore, the patient was diagnosed with an ICC involving the right glissonean pedicle and underwent a right hepatectomy and lymph node dissection. Histologic examination revealed the tumor consisted of moderately differentiated adenocarcinoma. In connection with this lesion, diffuse intraductal atypical epithelial cells, which were diagnosed as high-grade BilIN, was observed not only in the dilated B6 but in the entire posterior bile ducts, which measured approximately 120 mm in diameter. Furthermore, two distinct foci of adenocarcinomas were identified in the peripheral hepatic parenchyma. A lymph node metastasis was also present. The pathological diagnosis was ICC pT4N1M0 stage IVA. The patient underwent adjuvant chemotherapy and has shown no recurrence 5 years after surgery. Imaging modalities were unable to accurately assess the extent of the intraductal neoplastic lesions due to their low papillary or sessile intraductal tubular growth. No risk factors for BilIN development, which has the potential to predispose to cholangiocarcinoma, were identified in the present case. CONCLUSIONS: We present a case of ICC involving the right hepatic hilum, accompanied by extensive longitudinal extensions of high-grade BilIN and multifocal microscopic invasions in peripheral hepatic parenchyma. Notably, the intraductal lesions involved the entire posterior intrahepatic bile ducts. The presence of biliary neoplasia with extensive intraductal extension, in conjunction with ICC, should be considered as a variant of BilIN.

A prospective feasibility study of uracil-tegafur and leucovorin as adjuvant chemotherapy for patients aged ≥ 80 years after curative resection of colorectal cancer, the HiSCO-03 study.

PURPOSE: There is no consensus on the safety and effectiveness of adjuvant chemotherapy for patients with stage III colorectal cancer (CRC) aged ≥ 80 years. We conducted a prospective multi-institutional phase II study of uracil-tegafur and leucovorin (UFT/LV) as adjuvant chemotherapy in this population. PATIENTS AND METHODS: Patients with stage III CRC aged ≥ 80 years who underwent curative resection were enrolled. Eligible patients received UFT/LV therapy (UFT, 300 mg/m2 per day as tegafur; LV, 75 mg/day on days 1-28, every 35 days for five courses). Primary endpoint was feasibility, and secondary endpoints were safety and relative dose intensity. RESULTS: Sixty-nine patients were enrolled between 2013 and 2021. Of the 69 patients, 65 were included in the analysis. There were 32 males and 33 females with a median age of 82 years (range 80-88 years). In the primary endpoint, administration completion rate was 67.3% (95% confidence interval 54.9-77.6%), and the lower limit of the 95% confidence interval was below the threshold of 60%. 21 patients discontinued treatment because of adverse events (AEs) and refused treatment. The median relative dose intensities were 84% (range 4-100%) for UFT, and 100% (range 4-100%) for LV. Incidence of grade three or higher AEs were neutropenia (1.5%), aspartate transaminase elevation (3%), alanine transaminase elevation (1.5%), oral mucositis (3%), anemia (1.5%), and diarrhea (4.6%). CONCLUSIONS: The indications for adjuvant UFT/LV therapy for elderly CRC aged ≥ 80 years were considered limited. It is necessary to clarify the background of patients in whom drug administration is discontinued and investigate their impact on long-term prognosis.

Intracholecystic Papillary Neoplasm Localized to the Cystic Duct: A Case Report.

Intracholecystic papillary neoplasm (ICPN) of the gallbladder is a premalignant lesion. An ICPN arising from the cystic duct is rare. A woman in her 60s exhibited dilatation of the common bile duct on computed tomography (CT) performed for screening of respiratory disease. The CT revealed an enhancing mass, 3.3 cm in diameter, in the cystic duct. Endoscopic ultrasonography showed a well-demarcated, hyperechoic mass in the dilated cystic duct. Endoscopic retrograde cholangiography showed that the common bile duct was slightly retracted by the dilated cystic duct. Cytological analysis of the bile juice did not show any evidence of malignancy. She was diagnosed with a cystic bile duct tumor suggestive of ICPN. Cholecystectomy, resection of the extrahepatic bile duct, and lymph node dissection were performed. Macroscopically, the papillary-proliferated tumor was localized to the cystic duct. No critical lesions were evident in the common bile duct. Histologically, the tumor in the cystic duct showed intraluminal growth with a papillary configuration without malignancy. Based on these findings, the tumor was diagnosed as an ICPN. We encountered a rare case of ICPN localized to the cystic duct of the gallbladder.

Small bowel cancer arising from a scar site more than 60 years after ileostomy closure: a case report.

Although small bowel cancer is rare, cases of carcinoma arising from the abdominal wall have not been reported. We report a case of a tumor arising from a stoma scar site, following ileostomy closure that was performed 60 years earlier. The tumor was resected for both therapeutic and diagnostic purposes and was found to be a primary cancer of the small intestine. The small intestinal mucosa survived long-term at the stoma scar site and developed carcinoma. No similar reports of small bowel cancer arising from the mucosa at the stoma scar site (on the abdominal wall) exist. After tumor resection, the patient received chemotherapy for lung metastases and has survived, thus far, for 2 years since the surgery.

Locally advanced gallbladder cancer treated with effective chemotherapy and subsequent curative resection: a case report.

BACKGROUND: Surgical resection of gallbladder cancer with negative margins is the only potentially curative therapy. Most patients with gallbladder cancer are diagnosed in an advanced stage and, despite the availability of several chemotherapies, the prognosis remains dismal. We report a case of locally advanced gallbladder cancer that was successfully treated with effective cisplatin plus gemcitabine, followed by curative resection. CASE PRESENTATION: A 55-year-old Japanese female was hospitalized with right hypochondrial pain. Enhanced computed tomography revealed a 49 × 47 mm mass at the neck of the gallbladder, with suspected invasion of the liver and right hepatic artery. Endoscopic retrograde cholangiopancreatography demonstrated displacement of the upper bile duct. Intraductal ultrasonography showed irregular wall thickening and disappearance of the wall structure in bile ducts from the B4 branch to distal B2 and B3. Percutaneous transhepatic biliary biopsy revealed a poorly differentiated carcinoma. The patient was diagnosed with unresectable gallbladder cancer (T4N0M0 stage IVA). Cisplatin plus gemcitabine chemotherapy was initiated. After six courses of chemotherapy, enhanced computed tomography showed that the mass in the neck of the gallbladder had shrunk to 30 mm, Endoscopic retrograde cholangiopancreatography showed improvement of the hilar duct stenosis. A biopsy of the bile duct mucosa showed no malignant cells in the branch of the left and right hepatic ducts, the left hepatic duct, or the intrapancreatic ducts. The patient underwent conversion surgery with right and segment 4a liver resection, extrahepatic duct resection, and cholangiojejunostomy. The histopathologic diagnosis showed that the tumor cells had shrunk to 2 × 1 mm, and that R0 resection of the T2aN0M0 stage IIA tumor was successful. CONCLUSION: Although conversion surgery for gallbladder cancer is rarely possible, curative resection may offer a better prognosis, and it is important to regularly pursue possibilities for surgical resection even during chemotherapy.

A duodenal gastrointestinal stromal tumor mimicking a pancreatic neuroendocrine tumor: a case report.

BACKGROUND: Duodenal gastrointestinal stromal tumors are rare. If tumor growth is extraluminal and involves the head of the pancreas, the diagnosis of a duodenal gastrointestinal stromal tumor is difficult. CASE PRESENTATION: A 44-year-old Japanese woman was referred to our hospital with anemia. An enhanced computed tomography scan showed a hypervascular mass 30 mm in diameter, but the origin of the tumor, either the duodenum or the head of the pancreas, was unclear. Upper gastrointestinal endoscopy revealed bulging accompanied by erosion and redness in part of the duodenal bulb. Mucosal biopsy was not diagnostic. Endoscopic ultrasound fine-needle aspiration was difficult to perform because a pulsating blood vessel was present in the region to be punctured. These findings led to a diagnosis of pancreatic neuroendocrine tumor invasion to the duodenum. The patient underwent pancreaticoduodenectomy. Histologically, the tumor was made up of spindle-shaped cells immunohistochemically positive for c-Kit and CD34. The tumor was ultimately diagnosed as a duodenal gastrointestinal stromal tumor. CONCLUSION: Extraluminal duodenal gastrointestinal stromal tumors are rare and mimic pancreatic neuroendocrine tumors. Endoscopic ultrasound fine-needle aspiration is useful for preoperative diagnosis, but it is not possible in some cases. Intraoperative diagnosis based on a completely resected specimen of the tumor may be useful for modifying the surgical technique.