Introduction of a new surgical robot platform "hinotori™" in an institution with established da Vinci surgery™ for digestive organ operations.

BACKGROUND: New platforms for robotic surgery have recently become available for clinical use; however, information on the introduction of new surgical robotic platforms compared with the da Vinci™ surgical system is lacking. In this study, we retrospectively determined the safe introduction of the new "hinotori™" surgical robot in an institution with established da Vinci surgery using four representative digestive organ operations. METHODS: Sixty-one patients underwent robotic esophageal, gastric, rectal, and pancreatic operations using the hinotori system in our department in 2023. Among these, 22 patients with McKeown esophagectomy, 12 with distal gastrectomy, 11 with high- and low-anterior resection of the rectum, and eight with distal pancreatectomy procedures performed by hinotori were compared with historical controls treated using da Vinci surgery. RESULTS: The console (cockpit) operation time for distal gastrectomy and rectal surgery was shorter in the hinotori group compared with the da Vinci procedure, and there were no significant differences in the console times for the other two operations. Other surgical results were almost similar between the two robot surgical groups. Notably, the console times for hinotori surgeries showed no significant learning curves, determined by the cumulative sum method, for any of the operations, with similar values to the late phase of da Vinci surgery. CONCLUSIONS: This study suggests that no additional learning curve might be required to achieve proficient surgical outcomes using the new hinotori surgical robotic platform, compared with the established da Vinci surgery.

[A Case of Consciousness Disorder Due to Hyperammonemia Induced by Modified FOLFOX6 for Multiple Liver Metastasis from Rectal Cancer].

A 74-year-old man underwent laparoscopic-assisted high anterior resection with D3 lymph node dissection for rectal cancer, which was simultaneously accompanied by multiple liver metastases. The patient received mFOLFOX6 therapy for liver metastases 1 month after the surgery. Anorexia, nausea, and vomiting appeared on the second day of treatment. On the third day of treatment, impaired consciousness(JCS Ⅱ-20)and flapping tremors appeared. Blood tests revealed hyperammonemia, and the patient was diagnosed with impaired consciousness due to hyperammonemia, which was inferred to be caused by 5-fluorouracil(5-FU). Intravenous infusion and branched-chain amino acids were administered, and the patient recovered. The underlying disease of renal dysfunction, constipation, and dehydration due to chemotherapy might have induced the hyperammonemia. It is important to note that hyperammonemia can lead to a disturbance of consciousness during chemotherapy including 5-FU.

[Ascending colon cancer with submucosal tumor-like morphology arising near ileal valve lipohyperplasia:a case report].

An 89-year-old man was diagnosed with a submucosal tumor suspected to be a lipoma and was followed up for 6 years. The patient was admitted to the hospital because of increased tumor size and morphological changes despite negative bioptic findings. The lesion was diagnosed as an advanced adenocarcinoma of the ascending colon (cT3N0M0, cStage IIa). Laparoscopic-assisted right hemicolectomy with D3 lymph node dissection was performed. Pathological diagnosis of a surgically resected specimen revealed adenocarcinoma with lipohyperplasia (pT3N2aM0, pStage IIIb). Reports of colon cancer accompanied by colonic lipomas or lipohyperplasia are limited. This case showed an interesting submucosal tumor-like morphology because the cancer developed at the base of the lipohyperplasia and grew and spread below it.

A prospective randomized study of multimodal analgesia combined with single injection transversus abdominis plane block versus epidural analgesia against postoperative pain after laparoscopic colon cancer surgery.

PURPOSE: Transversus abdominis plane (TAP) block is a safe, effective, and promising analgesic procedure, but TAP block only cannot overcome postoperative pain. We conducted a prospective randomized study to evaluate postoperative pain control using multimodal analgesia (MA) combined with a single injection TAP block compared with epidural analgesia (EA) after laparoscopic colon cancer surgery. METHODS: Sixty-seven patients scheduled for elective laparoscopic colon cancer surgery were enrolled in this study and randomized into EA and MA groups. The primary endpoint was the frequency of additional analgesic use until postoperative day (POD) 2. The VAS score, blood pressure, time to bowel movement, time to mobilization, postoperative complications, and length of hospital stay were also compared between the two groups. RESULTS: Sixty-four patients (EA group, n = 33; MA group, n = 31) were analyzed. The patient characteristics did not differ markedly between the two groups. The frequency of additional analgesic use was significantly lower in the MA group than in the EA group (P < 0.001), whereas the VAS score did not differ markedly between the two groups. The postoperative blood pressure on the day of surgery was significantly lower in the MA group than in the EA group (P = 0.016), whereas urinary retention was significantly higher in the EA group than in the MA group (P < 0.001). CONCLUSION: MA combined with a single injection TAP block after laparoscopic colon cancer surgery may be comparable to EA in terms of analgesia and superior to EA in terms of urinary retention.

Retrospective risk analysis for acute urinary dysfunction after laparoscopic rectal cancer surgery in patients receiving epidural analgesia.

PURPOSE: Urinary dysfunction (UD) is a frequent complication following rectal surgery. The aim of the present study was to investigate the risk factors for acute UD after laparoscopic low anterior resection (LALAR) for rectal cancer in patients receiving epidural analgesia. METHODS: A retrospective study was conducted on 131 patients who underwent LALAR among those receiving epidural analgesia in a single institution between October 2008 and December 2019. Univariate and multivariate analyses were performed to determine the clinicopathological factors associated with acute UD. RESULTS: The overall incidence of acute UD was 16.0% (21/131). Univariate analysis showed that older age (P = 0.016) and earlier urinary catheter removal (P = 0.036) were associated with acute UD. Multivariate logistic regression analysis revealed that older age (10-year increments; odds ratio (OR) 2.046, 95% confidence interval (CI) 1.171-3.543, P = 0.011), urinary catheter removal before epidural analgesia discontinuation (OR 6.393, 95% CI 1.540-26.534, P = 0.011), and a large tumor circumference rate (10% increments; OR 1.263, 95% CI 1.043-1.530, P = 0.017) were independent risk factors for acute UD. CONCLUSION: Our findings suggest that older age, early removal of urinal catheter before epidural analgesia discontinuation, and large tumor circumference rate are risk factors of acute UD after LALAR for rectal cancer in patients receiving epidural analgesia.

The risk factors of acute urinary retention after laparoscopic colorectal cancer surgery in elderly patients receiving epidural analgesia.

PURPOSE: Urinary retention (UR) is a frequent complication following laparoscopic colorectal surgery. The aim of the present study was to investigate the risk factors for acute UR after laparoscopic surgery for colorectal cancer in patients receiving epidural analgesia. METHODS: A retrospective study was conducted of 201 patients who underwent laparoscopic surgery for colorectal cancer among those receiving epidural analgesia. Univariate and multivariate analyses were performed to determine the clinicopathological factors associated with acute UR. Acute UR was defined as Clavien-Dindo classification grade ≥ 1. RESULTS: The overall incidence of acute UR was 17.9% (36/201). The univariate analysis showed that male gender (P = 0.043), a history of chronic heart failure (P = 0.009), an increased level of serum creatinine (P = 0.028), an increased intraoperative fluid volume (P = 0.016), and an early postoperative date of urinary catheter removal (P = 0.003) were both associated with acute UR. The multivariate logistic regression analysis revealed an increased intraoperative fluid volume (100-ml increments; odds ratio [OR]: 1.085, 95% confidence interval [CI]: 1.034-1.138, P < 0.001), history of chronic heart failure (OR: 6.843, 95% CI: 1.893-24.739, P = 0.003), and postoperative date of urinary catheter removal (OR: 0.550, 95% CI: 0.343-0.880, P = 0.013) were independent risk factors for acute UR. CONCLUSION: Our findings suggest that an increased intraoperative fluid volume, history of chronic heart failure, and early removal of the urinary catheter are risk factors of UR after laparoscopic surgery for colorectal cancer in patients receiving epidural analgesia. An assessment using these factors might be helpful for predicting acute UR.

A clinical risk analysis of early post-operative delirium after laparoscopic colorectal cancer surgery in elderly patients: a retrospective study.

PURPOSE: Early post-operative delirium (EPOD) is a frequent complication following colorectal surgery. The present study investigated the risk factors for EPOD after laparoscopic colorectal surgery in elderly patients. METHODS: A retrospective study was conducted among 208 patients ≥70 years old who underwent laparoscopic colorectal surgery. Univariate and multivariate analyses were performed to determine the clinicopathological factors associated with the EPOD. RESULTS: The overall incidence of EPOD was 10.1% (21/208). The univariate analysis showed that an older age (≥80 years old; P=0.002), sleeping pill medication before surgery (P=0.037), a history of dementia (P=0.030) and cerebrovascular disease (P=0.017), elevated levels of D-dimer (P=0.016), maximum intraoperative temperature ≥37 °C (P=0.036), and non-continuous usage of droperidol with analgesia (P=0.005) were associated with EPOD. The multivariate logistic regression analysis revealed an older age (≥80 years old; odds ratio [OR]: 6.26, 95% confidence interval [CI]: 1.94-20.15, P=0.002), sleeping pill medication before surgery (OR: 5.39, 95% CI: 1.36-21.28, P=0.016), history of cerebrovascular disease (OR: 3.91, 95% CI: 1.12-13.66, P=0.033), and maximum intraoperative temperature ≥37 °C (OR: 5.10, 95% CI: 1.53-16.92, P=0.008) to be independent risk factors. When the patients were divided into groups according to the number of positive risk factors, the prevalence rate was 6.5%, 16.0%, and 63.6% for patients with 1, 2, and 3 positive risk factors, respectively. CONCLUSION: Our findings suggest that an older age, sleeping pill medication before surgery, history of cerebrovascular disease, and maximum intraoperative temperature ≥37 °C are independent risk factors of EPOD after laparoscopic colorectal surgery in elderly patients.

Peritoneal adenomatoid (microcystic) mesothelioma.

There are several reports of pleural adenomatoid (microcystic) mesothelioma, but peritoneal adenomatoid mesothelioma is extremely rare. A 64-year-old Japanese woman presented with no symptoms and no asbestos exposure history. An abdominal computed tomography scan revealed multiple hypervascular masses on the liver surface, pelvic cavity and anterior peritoneum. Over 10 pieces of the multiple resected tumors showed numerous microcysts composed of a bland mesothelial cell background with rich capillary vessels. Focally, atypical cells with bizarre nuclei with prominent nucleoli were observed. Adenomatoid mesothelioma was suspected based on histochemical, immunohistochemical and fluorescence in situ hybridization findings. The tumors relapsed 4 years later and metastasized to the lung, but the patient remains alive 7 years after the first tumor resection surgery. Although the prognosis of adenomatoid mesothelioma of pleural origin is poor, the progression of this peritoneal case is slow.

Precision CT­guided marking with India ink and microcoils for laparoscopic resection of a lateral lymph node recurrence of rectal cancer: A case report.

Although rarely used in laparoscopic surgery, computed tomography (CT)-guided marking is useful for targeting small lesions. The present study describes the performance of laparoscopic resection with preoperative CT-guided marking for lateral lymph node recurrence of rectal cancer. A 48-year-old man underwent laparoscopic low anterior resection with D3 lymph node dissection for rectal cancer (postoperative diagnosis, stage IIIb). Postoperative adjuvant chemotherapy was then administered. Solitary lymph node recurrence was observed in the left lateral region after 6 months. Systemic chemotherapy reduced the size of the metastatic lymph nodes; however, 3.5 years after the surgery, the diameter increased by 10 mm, and laparoscopic resection was thus planned. Because the target lesion was small and located deep in the pelvis, preoperative CT-guided marking was performed with India ink injection and embolization microcoil implantation. The markers were clearly identified and the lesion was successfully resected with adequate margins. The approach described in the present study is thus considered potentially useful for the detection of small lesions.

The Clinical Impact of Apical Lymph Node Metastasis of Colorectal Cancer After Curative Resection.

PURPOSE: The present study aimed to investigate the clinical implications of apical lymph node metastasis (ALNM) after curative resection of stage III colorectal cancer. METHODS: A retrospective study was conducted of 1403 consecutive colorectal cancer patients who underwent surgical resection at a single institution between April 2008 and January 2020. The characteristics of ALNM, the recurrence status and the relapse-free survival (RFS) were examined. RESULTS: The numbers of patients with stage ≤ I, II, III, and IV disease were 350, 437, 476, and 140 patients, respectively. Among these patients with stage III disease, ALNM was seen in 21 patients (4.4% of stage III patients). Among them, curative resection was performed in 19 patients. Recurrence was observed in 68% (13/19) of the patients with ALNM who received curative resection. The first sites of recurrence included the lymph nodes 53.8% (7/13), liver 30.8% (4/13), lung 15.4% (2/13), brain 7.7% (1/13), bone 7.7% (1/13), and peritoneum 7.7% (1/13). There was no significant difference in the RFS of patients with ALNM who were managed with or without adjuvant chemotherapy (P = 0.207). Furthermore, the RFS of the group managed without adjuvant chemotherapy and the group that received adjuvant chemotherapy with/without oxaliplatin did not differ to a statistically significant extent (P = 0.318). In stage III colorectal cancer patients with ALNM, recurrence was observed significantly more frequently in comparison to stage III colorectal cancer patients without ALNM (P = 0.007). The first site of recurrence in patients with ALNM was most frequently seen in the distant lymph nodes (P = 0.004). CONCLUSION: Our findings suggest that ALNM is strongly associated with recurrence in the distant lymph nodes and that it may lead to the development of systemic disease. The current regimen for stage III colorectal cancer may therefore not be sufficient for patients with stage III ALNM.

Laparoscopic surgery for rectal cancer with a coexisting Retzius shunt and inferior mesenteric arteriovenous malformation: A case report.

A coexisting short-circuit from the inferior mesenteric vein (IMV) to the inferior vena cava, known as a Retzius shunt, and arteriovenous malformation (AVM) of the inferior mesentery are extremely rare conditions. We encountered a case of rectal cancer with coexisting Retzius shunt and inferior mesenteric AVM successfully treated with laparoscopic surgery. Contrast computed tomography (CT) in a 62-year-old man with rectal cancer showed multiple dilated veins at the mesenterium of the descending sigmoid colon. These dilated veins were connected between the IMV and the left renal vein. A diagnosis of Retzius shunt was made, and laparoscopic low anterior resection with lymph node dissection was performed. A pathological examination of the colonic mesenterium revealed AVM communicating with the dilated IMV and Retzius shunt. The preoperative evaluation of aberrant vessels by three-dimensional CT is particularly useful for patients with vascular malformations to ensure safe laparoscopic surgery.

The analysis of fecal calprotectin as a diagnostic marker for anastomotic leakage after rectal cancer surgery: a pilot study.

A prospective pilot study was conducted on 11 patients with rectal cancer to investigate fecal calprotectin (FC) as a diagnostic tool for detecting anastomotic leakage (AL) after low anterior resection. Among the 11 patients, 1 patient (9.1%) experienced AL (Clavien-Dindo Grade IIIa). During the post-operative course until post-operative day (POD) 5, the white blood cell count of the patient with AL was within the normal range. The C-reactive protein level in the AL and non-AL groups showed a similar time course. On the other hand, the FC level in patient with AL dramatically increased on POD5, while the FC level of the non-AL group remained relatively stable. There was no significant correlation between the preoperative FC level and the tumor circumference rate, tumor size, depth of invasion or stage. This pilot study showed the possibility of FC as a useful diagnostic tool for the detection of AL after low anterior resection for rectal cancer.

The Oncological Effect of Mutant p53 on the Metastatic Phenotype of Gastric Cancer Cells.

BACKGROUND/AIM: P53 is the most frequently mutated tumor suppressor gene among all cancers. In human cancers, specific residues of p53 are mutated at a high frequency, and those mutations are known as hotspot mutations. Mutant p53 promotes tumor progression through the gain-of-function (GOF) mechanism. However, its biological characteristics, especially its metastatic potential, owing to different hotspot mutations in gastric cancer remain unclear. In the present study, we investigated the p53-depended metastatic phenotype. MATERIALS AND METHODS: This study examined the differences in the metastatic potential of wild-type, mutant-p53-R175H, and mutant-p53-R273H NUGC-4 gastric cancer cells in vitro and in vivo. RESULTS: NUGC-4-mutant-p53-R175H cells showed significant cell proliferation, healing and invasive abilities in proliferation, wound healing and invasion assay, respectively, compared to wild-type and mutant-p53-R273H cells. Both NUGC-4-mutant-p53 cell types expressed epithelial-mesenchymal transition (EMT)-related proteins. Furthermore, NUGC-4-mutant-p53-R175H cells showed less attachment to the extracellular matrix and greater expression of EMT-related proteins than NUGC-4-mutant-p53-R273H cells. Regarding the peritoneal dissemination model, NUCG-4-mutant-p53-R175H and NUCG-4-mutant-p53-R273H cells demonstrated less frequent formation of dissemination nodules than NUGC-4-empty cells. In contrast, liver metastases were more frequent and greater in number in NUCG3-mutant-p53-R175H than in the other cell lines. CONCLUSION: Our results suggest that differences in the p53 status, even in the hotspot mutation site, affect not only the characteristics of the cells but also the metastatic ability of gastric cancer.

A rare case of inflammatory myofibroblast tumor of the stomach successfully treated by inverted laparoscopic and endoscopic cooperative surgery.

BACKGROUND: An Inflammatory myofibroblastic tumor (IMT) is a rare intermediate malignancy characterized by myofibroblast proliferation and inflammatory cell infiltration. Various organs are the primary sites of origin. However, primary tumors originating in the stomach tend to be extremely rare, making the diagnosis difficult. Herein, we present a case of IMT originating in the stomach that was effectively managed using inverted laparoscopic endoscopic cooperative surgery (LECS). CASE PRESENTATION: A 47-year-old male who was admitted to the hospital because of a submucosal tumor that was discovered during upper gastrointestinal endoscopy. The diameter of the tumor was approximately 20 mm. A KIT-negative gastrointestinal stromal tumor was suspected based on the biopsy findings. Therefore, partial resection of the stomach was performed using inverted laparoscopic and endoscopic cooperative surgery. Histopathological examination revealed collagen fiber proliferation from the submucosal layer to the muscular layer, accompanied by infiltration of spindle-shaped cells, lymphocytes, and numerous inflammatory cells. Immunohistochemistry results were positive for SMA and negative for CD34, desmin, and c-kit. IgG4-positive cells were observed with an IgG4/IgG ratio > 50%, and specific nuclei were positive for ALK. Therefore, IMT was diagnosed. This condition may be difficult to diagnose both before and after surgery because of its rarity and submucosal tumor-like morphology. CONCLUSION: When a submucosal tumor originating in the stomach is observed, IMT should be considered. Partial resection of the stomach with LECS and immunohistochemical diagnosis may be useful.

Expression of hypoxic marker CA IX is regulated by site-specific DNA methylation and is associated with the histology of gastric cancer.

The hypoxic marker carbonic anhydrase (CA) IX has been recognized as a tumor-associated protein and is essential for cancer development. However, because CA IX expression does not always correlate with hypoxia, its regulatory mechanism remains unclear. The objective of the present study was to clarify the role and regulation of CA IX expression in gastric cancer. The immunohistochemical expression of CA IX and hypoxia-inducible factor-1α was assessed in 77 patients with gastric cancer. A methylation-sensitive restriction enzyme method was used to quantify site-specific methylation at -74 bp in the CA9 promoter in tissue from patients with gastric cancer and in corresponding normal tissue. CA9 expression in cell lines was strongly dependent on methylation status but not hypoxic stimuli. In tissue from patients with gastric cancer, the quantity of methylation was significantly correlated with the protein expression (P = 0.003). Moreover, the methylation value was significantly lower in intestinal-type compared with diffuse-type cancer (P = 0.003). Compared with normal mucosa, intestinal-type cancer demonstrated significant hypomethylation, whereas diffuse-type cancer exhibited hypermethylation. In conclusion, expression of CA IX in gastric cancer is predominantly regulated by methylation of a single CpG rather than by hypoxia. Furthermore, epigenetic alterations in CA9 differ between the intestinal and diffuse types of gastric cancer.

Laparoscopic Training for Gastrointestinal Surgery Using Japanese Traditional Papercraft Origami.

PURPOSE: The aim of this study is to show the experience and results of laparoscopic training using origami, a Japanese traditional papercraft, and to discuss its usefulness in gastrointestinal surgery. MATERIALS AND METHODS: A laparoscopic training dry box was used. An origami paper crane was folded using laparoscopic instruments. The time to complete the origami crane was measured. RESULTS: Two trainees participated in this study; the total number of origami cranes folded by these trainees was 2000 and 700, respectively. The learning curve gradually improved. According to our experience, this training strengthened mental faculties and was associated with the improvement of hand-eye and left-right coordination, reduction of tremor, acquisition of delicate technique, the ability to distinguish subtle differences in color, ability to respond to trouble. CONCLUSIONS: Laparoscopic training for gastrointestinal surgery using origami may have the potential to improve the technical skills in laparoscopic surgery.

Risk factors of incisional hernia at the umbilical specimen extraction site in patients with laparoscopic colorectal cancer surgery.

Purpose: Incisional hernia (IH) is a frequent complication following laparoscopic colorectal surgery. The present study investigated the risk factors for IH after laparoscopic surgery for colorectal cancer. Methods: A retrospective study was conducted on 202 patients who underwent laparoscopic surgery for colorectal cancer. Univariate and multivariate analyses were performed to determine the clinicopathological factors associated with IH. Results: The overall incidence of IH was 25.7% (52 of 202). The univariate analysis showed that female sex (P=0.004), a high body mass index (P<0.001), non-current smoking habit (P=0.043), low level of hemoglobin (P=0.035), high subcutaneous fat area (P<0.001), high visceral fat area (P=0.006), low skeletal muscle area (P=0.001), long distance between the inner edges of the rectus abdominis muscle (P=0.001), long protrusion of the peritoneum at the umbilical site (P<0.001), and lymph node metastasis (P=0.007) were significantly more frequent in the group with IH than in the group without it. The multivariate logistic regression analysis revealed an older age (10-year increments: odds ratio [OR], 1.576; 95% confidence interval [CI], 1.027-2.419; P=0.037), lymph node metastasis (OR, 2.384; 95% CI, 1.132-5.018; P=0.022) and lengthy protrusion of the peritoneum at the umbilical site (10-mm increments: OR, 5.555; 95% CI, 3.058-10.091; P<0.001) were independent risk factors for IH. Conclusion: Our findings suggest that older age, lymph node metastasis, and lengthy protrusion of the peritoneum at the umbilical site are risk factors for IH after laparoscopic surgery for colorectal cancer. An assessment using these factors before the operation and the implementation of countermeasures might help prevent IH.

Intussusception of the cecum due to the acute appendicitis: A case report.

INTRODUCTION AND IMPORTANCE: Intussusception of the cecum due to acute appendicitis is rare condition. PRESENTATION OF CASE: A 17-year-old male patient presented to our hospital with a chief complaint of right lower abdominal pain, which had lasted for two days. Computed tomography (CT) revealed a "target sign" from the cecum to the ascending colon, leading to a diagnosis of cecocolic intussusception. Colonoscopy revealed an erythematous, edematous, and internally distorted cecum in the ascending colon, which was difficult to repair with air insufflation. Laparoscopic surgery was performed to remove the bowel obstruction. Repositioning of the invaginated cecum was difficult due to the presence of a hard and edematous colic wall. Therefore, laparoscopic ileocecal resection was performed to release the obstruction. The pathological diagnosis was appendicitis and abscess within the cecum wall, with no malignant findings. DISCUSSION: In our case, intussusception was considered to have caused thickening of the intestinal wall of the cecum due to inflammation of the appendix, and the thickened area became the leading point. CONCLUSION: Considering that malignancy is a frequent leading point in adult patients with intussusception, a preoperative endoscopic examination is important for minimizing bowel resection.

Aberrant gene methylation is a biomarker for the detection of cancer cells in peritoneal wash samples from advanced gastric cancer patients.

PURPOSE: To assess whether gene methylation in peritoneal fluid (PF) is clinically feasible for determining micrometastasis to the peritoneum in gastric cancer. METHODS: The gene methylation of BNIP3, CHFR, CYP1B1, MINT25, SFRP2, and RASSF2 were analyzed in 107 specimens of PF by quantitative methylation-specific polymerase chain reaction. All patients were placed into one of 3 groups: group A (n = 42), patients with depth of cancer invasion at muscularis propria (MP) or less than MP; group B (n = 45), depth of cancer invasion beyond the MP; and group C (n = 20), histologically diagnosed peritoneal metastasis or cancer cells cytologically defined in the peritoneal cavity. Patients in both groups A and B were diagnosed as having no cancer cells by peritoneal cytology and histology. RESULTS: The methylation status of the 6 genes was found to be significantly different among the 3 groups (group A, 0-5%; group B, 0-15%; group C, 15-45%; P < 0.01). Furthermore, the rate of positive methylation in any of the 6 genes was significantly different in each group (group A, 7%; group B, 20%; group C, 75%; P < 0.001). Three of 9 patients in group B with positive methylation in any of 6 genes experienced peritoneal recurrence. On the other hand, only 1 of 36 patients without gene methylation experienced peritoneal recurrence (P < 0.05). CONCLUSIONS: DNA methylation in PFs is a possible marker detecting occult neoplastic cells on the peritoneum. Methylation analysis along with a cytological examination might therefore improve the positive detection of cancer cells in PF of gastric cancer.