A Runx1-enhancer Element eR1 Identified Lineage Restricted Mammary Luminal Stem Cells.

Mammary gland homeostasis is maintained by adult tissue stem-progenitor cells residing within the luminal and basal epithelia. Dysregulation of mammary stem cells is a key mechanism for cancer development. However, stem cell characterization is challenging because reporter models using cell-specific promoters do not fully recapitulate the mammary stem cell populations. We previously found that a 270-basepair Runx1 enhancer element, named eR1, marked stem cells in the blood and stomach. Here, we identified eR1 activity in a rare subpopulation of the ERα-negative luminal epithelium in mouse mammary glands. Lineage-tracing using an eR1-CreERT2 mouse model revealed that eR1+ luminal cells generated the entire luminal lineage and milk-secreting alveoli-eR1 therefore specifically marks lineage-restricted luminal stem cells. eR1-targeted-conditional knockout of Runx1 led to the expansion of luminal epithelial cells, accompanied by elevated ERα expression. Our findings demonstrate a definitive role for Runx1 in the regulation of the eR1-positive luminal stem cell proliferation during mammary homeostasis. Our findings identify a mechanistic link for Runx1 in stem cell proliferation and its dysregulation in breast cancer. Runx1 inactivation is therefore likely to be an early hit in the cell-of-origin of ERα+ luminal type breast cancer.

Induction of Gastric Cancer by Successive Oncogenic Activation in the Corpus.

BACKGROUND & AIMS: Metaplasia and dysplasia in the corpus are reportedly derived from de-differentiation of chief cells. However, the cellular origin of metaplasia and cancer remained uncertain. Therefore, we investigated whether pepsinogen C (PGC) transcript-expressing cells represent the cellular origin of metaplasia and cancer using a novel Pgc-specific CreERT2 recombinase mouse model. METHODS: We generated a Pgc-mCherry-IRES-CreERT2 (Pgc-CreERT2) knock-in mouse model. Pgc-CreERT2/+ and Rosa-EYFP mice were crossed to generate Pgc-CreERT2/Rosa-EYFP (Pgc-CreERT2/YFP) mice. Gastric tissues were collected, followed by lineage-tracing experiments and histologic and immunofluorescence staining. We further established Pgc-CreERT2;KrasG12D/+ mice and investigated whether PGC transcript-expressing cells are responsible for the precancerous state in gastric glands. To investigate cancer development from PGC transcript-expressing cells with activated Kras, inactivated Apc, and Trp53 signaling pathways, we crossed Pgc-CreERT2/+ mice with conditional KrasG12D, Apcflox, Trp53flox mice. RESULTS: Expectedly, mCherry mainly labeled chief cells in the Pgc-CreERT2 mice. However, mCherry was also detected throughout the neck cell and isthmal stem/progenitor regions, albeit at lower levels. In the Pgc-CreERT2;KrasG12D/+ mice, PGC transcript-expressing cells with KrasG12D/+ mutation presented pseudopyloric metaplasia. The early induction of proliferation at the isthmus may reflect the ability of isthmal progenitors to react rapidly to Pgc-driven KrasG12D/+ oncogenic mutation. Furthermore, Pgc-CreERT2;KrasG12D/+;Apcflox/flox mice presented intramucosal dysplasia/carcinoma and Pgc-CreERT2;KrasG12D/+;Apcflox/flox;Trp53flox/flox mice presented invasive and metastatic gastric carcinoma. CONCLUSIONS: The Pgc-CreERT2 knock-in mouse is an invaluable tool to study the effects of successive oncogenic activation in the mouse corpus. Time-course observations can be made regarding the responses of isthmal and chief cells to oncogenic insults. We can observe stomach-specific tumorigenesis from the beginning to metastatic development.

Predictors of early and late mortality after the treatment for early gastric cancers.

OBJECTIVES: Although many patients with early gastric cancers (EGCs) die of non-gastric cancer-related causes, the association of the risk categories of lymph node metastasis (LNM) with all-cause mortality remains unclear. We aimed to clarify the predictors of early and late mortality, separately. METHODS: Patients with endoscopic resection or gastrectomy for EGCs between 2003 and 2017 were retrospectively enrolled. We analyzed predictors for early and late mortality, including risk categories of LNM, treatment method, and nine non-cancer-related indices, separately, with a cut-off value of 3 years. RESULTS: We enrolled 1439 patients with a median follow-up period of 79 months. The 5-year overall survival rate was 86.8%. In the multivariate Cox analysis, the most important predictors for early and late mortality were age ≥85 years (hazard ratio [HR] 2.88 and 4.54, respectively) and Eastern Cooperative Oncology Group Performance Status ≥2 (HR 3.00 and 4.19, respectively). Charlson comorbidity index ≥2 (HR 2.76 and 1.99, respectively), American Society of Anesthesiologists Physical Status ≥3 (HR 2.35 and 1.79, respectively), and C-reactive protein/albumin ratio ≥0.028 (HR 2.30 and 1.58, respectively) were also predictors for both early and late mortality. Male (HR 2.26), intermediate- (HR 2.12)/high-risk (HR 1.85) of LNM in eCura system, and sarcopenia evaluated by the psoas muscle mass index (HR 1.70) were predictors for early mortality. CONCLUSION: The combined assessment of multiple predictors might help to predict early and/or late mortality in patients with EGCs. The eCura system was associated with early mortality.

The Mucus Binding Factor Is Not Necessary for Lacticaseibacillus rhamnosus CRL1505 to Exert Its Immunomodulatory Activities in Local and Distal Mucosal Sites.

Both viable and non-viable orally administered Lacticaseibacillus rhamnosus CRL1505 modulate immunity in local (intestine) and distal (respiratory) mucosal sites. So, intestinal adhesion and colonization are not necessary for this probiotic strain to exert its immunomodulatory effects. In this work, a mucus-binding factor knockout CRL1505 strain (ΔmbfCRL1505) was obtained and the lack of binding ability to both intestinal epithelial cells and mucin was demonstrated in vitro. In addition, two sets of in vivo experiments in 6-week-old Balb/c mice were performed to evaluate ΔmbfCRL1505 immunomodulatory activities. (A) Orally administered ΔmbfCRL1505 prior to intraperitoneal injection of the Toll-like receptor 3 (TLR3) agonist poly(I:C) significantly reduced intraepithelial lymphocytes (CD3+NK1.1+CD8αα+) and pro-inflammatory mediators (TNF-α, IL-6 and IL-15) in the intestinal mucosa. (B) Orally administered ΔmbfCRL1505 prior to nasal stimulation with poly(I:C) significantly decreased the levels of the biochemical markers of lung tissue damage. In addition, reduced recruitment of neutrophils and levels of pro-inflammatory mediators (TNF-α, IL-6 and IL-8) as well as increased IFN-ß and IFN-γ in the respiratory mucosa were observed in ΔmbfCRL1505-treated mice when compared to untreated control mice. The immunological changes induced by the ΔmbfCRL1505 strain were not different from those observed for the wild-type CRL1505 strain. Although it is generally accepted that the expression of adhesion factors is necessary for immunobiotics to induce their beneficial effects, it was demonstrated here that the mbf protein is not required for L. rhamnosus CRL1505 to exert its immunomodulatory activities in local and distal mucosal sites. These results are a step forward towards understanding the mechanisms involved in the immunomodulatory capabilities of L. rhamnosus CRL1505.

[Successful R0 Resection of Two Metachronous Krukenberg Tumors from Gastric Cancer-A Case Report].

A 50s woman with a stomachache was referred to our hospital with diagnosed gastric cancer. Upper endoscopy showed a type 3 tumor in the lower gastric body, and CT demonstrated a pelvic tumor 10 cm in size. Laparoscopic surgery was performed; since the pelvic tumor was found to derive from the left ovary, left oophorectomy and total gastrectomy were performed. Pathological examination revealed that the ovarian tumor was a gastric cancer metastasis. Adjuvant chemotherapy with S-1 monotherapy was introduced. Four months after the operation, metastasis was suspected due to right ovary tumor edema. Due to the possibility of obtaining R0 resection and adverse events of chemotherapy, we chose right oophorectomy. Pathological examination demonstrated signet-ring cell cancer. Fourteen months after the first operation, the patient is alive with no recurrence or metastasis.

[A Case of Multiple Gastric GIST with Lymph Nodes Metastases in a Young Woman].

A 21-year-old woman with bloody stool was referred to our hospital with multiple submucosal tumors at the posterior and anterior wall of the gastric angle under upper gastrointestinal endoscopy. Both of the tumors were diagnosed with gastric gastrointestinal stromal tumor(GIST)by EUS-FNA, then laparoscopic distal gastrectomy with D1 lymph node dissection was performed. The size of those tumors were 47 mm and 15 mm respectively, and pathological examination revealed multiple lymph nodes metastases. Neither KIT nor PDGFRA mutation was found. She had received postoperative adjuvant chemotherapy with imatinib mesylate for 3 years. No sign of recurrence has been confirmed thereafter. GISTs in young adults are rare and their oncological features are considered to be different from common type of GIST.

Iqgap3-Ras axis drives stem cell proliferation in the stomach corpus during homoeostasis and repair.

OBJECTIVE: Tissue stem cells are central regulators of organ homoeostasis. We looked for a protein that is exclusively expressed and functionally involved in stem cell activity in rapidly proliferating isthmus stem cells in the stomach corpus. DESIGN: We uncovered the specific expression of Iqgap3 in proliferating isthmus stem cells through immunofluorescence and in situ hybridisation. We performed lineage tracing and transcriptomic analysis of Iqgap3 +isthmus stem cells with the Iqgap3-2A-tdTomato mouse model. Depletion of Iqgap3 revealed its functional importance in maintenance and proliferation of stem cells. We further studied Iqgap3 expression and the associated gene expression changes during tissue repair after tamoxifen-induced damage. Immunohistochemistry revealed elevated expression of Iqgap3 in proliferating regions of gastric tumours from patient samples. RESULTS: Iqgap3 is a highly specific marker of proliferating isthmus stem cells during homoeostasis. Iqgap3+isthmus stem cells give rise to major cell types of the corpus unit. Iqgap3 expression is essential for the maintenance of stem potential. The Ras pathway is a critical partner of Iqgap3 in promoting strong proliferation in isthmus stem cells. The robust induction of Iqgap3 expression following tissue damage indicates an active role for Iqgap3 in tissue regeneration. CONCLUSION: IQGAP3 is a major regulator of stomach epithelial tissue homoeostasis and repair. The upregulation of IQGAP3 in gastric cancer suggests that IQGAP3 plays an important role in cancer cell proliferation.

Wnt5a in cancer-associated fibroblasts promotes colorectal cancer progression.

Cancer-associated fibroblasts (CAFs) are a major component of the tumor microenvironment and have been shown to promote cancer aggressiveness. In our previous study, analysis of expression profiles obtained from paired CAFs and normal fibroblasts from colorectal cancer (CRC) tissue revealed that gene sets related to the Wnt signaling pathway were highly enriched in colorectal CAFs. Furthermore, among the components of the ß-catenin-independent Wnt pathway, Wnt5a was highly expressed in CAFs. Since Wnt5a is considered to be a regulator of CRC progression in CAFs, we performed immunohistochemical analysis on Wnt5a in 171 patients who underwent surgery for CRC. Positive staining for Wnt5a was often found in cancer stroma, particularly in fibromatous areas, although the immunoreactivity for Wnt5a was weak in cancer cells. Wnt5a status in CAFs was significantly associated with tumor size, depth of invasion, lymphatic and vascular invasion, lymph node metastasis, TNM stage, and recurrence. Subsequent in vitro analyses using human recombinant Wnt5a protein revealed that cancer cell proliferation and migration were significantly increased by stimulation with Wnt5a. Our findings suggest that Wnt5a-derived CAFs play a crucial role in CRC progression and have potential as a target of anti-cancer therapies.

The association between ERK inhibitor sensitivity and molecular characteristics in colorectal cancer.

The mitogen-activated protein kinase (MAPK) pathway plays an important role in the colorectal cancer (CRC) progression, being supposed to be activated by the gene mutations, such as BRAF or KRAS. Although the inhibitors of extracellular signal-regulated kinase (ERK) have demonstrated efficacy in the cells with the BRAF or KRAS mutations, a clinical response is not always associated with the molecular signature. The patient-derived organoids (PDO) have emerged as a powerful in vitro model system to study cancer, and it has been widely applied for the drug screening. The present study aims to analyze the association between the molecular characteristics which analyzed by next-generation sequencing (NGS) and sensitivity to the ERK inhibitor (i.e., SCH772984) in PDO derived from CRC specimens. A drug sensitivity test for the SCH772984 was conducted using 14 CRC cell lines, and the results demonstrated that the sensitivity was in agreement with the BRAF mutation, but was not completely consistent with the KRAS status. In the drug sensitivity test for PDO, 6 out of 7 cases with either BRAF or KRAS mutations showed sensitivity to the SCH772984, while 5 out of 6 cases of both BRAF and KRAS wild-types were resistant. The results of this study suggested that the molecular status of the clinical specimens are likely to represent the sensitivity in the PDOs but is not necessarily absolutely overlapping. PDO might be able to complement the limitations of the gene panel and have the potential to provide a novel precision medicine.

A Phenylfurocoumarin Derivative Reverses ABCG2-Mediated Multidrug Resistance In Vitro and In Vivo.

The ATP-binding cassette subfamily G member 2 (ABCG2) transporter is involved in the development of multidrug resistance in cancer patients. Many inhibitors of ABCG2 have been reported to enhance the chemosensitivity of cancer cells. However, none of these inhibitors are being used clinically. The aim of this study was to identify novel ABCG2 inhibitors by high-throughput screening of a chemical library. Among the 5812 compounds in the library, 23 compounds were selected in the first screening, using a fluorescent plate reader-based pheophorbide a (PhA) efflux assay. Thereafter, to validate these compounds, a flow cytometry-based PhA efflux assay was performed and 16 compounds were identified as potential inhibitors. A cytotoxic assay was then performed to assess the effect these 16 compounds had on ABCG2-mediated chemosensitivity. We found that the phenylfurocoumarin derivative (R)-9-(3,4-dimethoxyphenyl)-4-((3,3-dimethyloxiran-2-yl)methoxy)-7H-furo [3,2-g]chromen-7-one (PFC) significantly decreased the IC50 of SN-38 in HCT-116/BCRP colon cancer cells. In addition, PFC stimulated ABCG2-mediated ATP hydrolysis, suggesting that this compound interacts with the substrate-binding site of ABCG2. Furthermore, PFC reversed the resistance to irinotecan without causing toxicity in the ABCG2-overexpressing HCT-116/BCRP cell xenograft mouse model. In conclusion, PFC is a novel inhibitor of ABCG2 and has promise as a therapeutic to overcome ABCG2-mediated MDR, to improve the efficiency of cancer chemotherapy.

[A Case of Remnant Gastric Cancer with Mesojejunal Lymph Node Metastasis].

A 62-year-old man underwent radical surgery for the treatment of remnant gastric cancer with mesojejunal lymph node metastasis. According to the 15th edition of the Japanese Gastric Cancer Association, a histological diagnosis of B-35-A, type 3, tub2>tub1, pT3(SS), pN3a(10/37), cM0, CY0, pStage ⅢB was made. All lymph node metastases were recognized in the mesojejunum. Adjuvant chemotherapy with S-1 plus docetaxel was initiated after 4 weeks of surgery. The patient is still alive without recurrence after 1 year of surgery. Thus, radical surgery with dissection of the mesojejunum and intensive adjuvant chemotherapy might improve the prognosis in a remnant gastric cancer patient with mesojejunal lymph node metastasis.

[Complete Response to Neoadjuvant Chemotherapy with Imatinib of a Large Gastric GIST-A Case Report].

A 54-year-old woman was presented with the intraabdominal mass to our hospital. Abdominal CT showed 22 cm tumor of the stomach with invasion to the pancreas and the spleen. Upper GI endoscopy showed submucosal tumor at the stomach body, and endoscopic US showed low echoic tumor. The tumor was diagnosed as gastric GIST by biopsy with c-kit positive cells. After 4 months of neoadjuvant therapy with imatinib, she underwent total gastrectomy, distal pancreatectomy and splenectomy. Histopathologically, there were no viable tumor cells in the resected specimen. The patient has no evidence of recurrence at 8 months post operation.

[A Case of Radically Resected Sigmoid Colon Cancer with Bladder Invasion after Chemotherapy and Weight Loss in an Extremely Obese Patient].

A 30's extremely obese patient(body mass index: BMI 45 kg/m2)was referred to our hospital with a chief complaint of bloody urine and stool. Colonoscopy revealed a sigmoid colon tumor. Barium enema examination revealed stenosis of the sigmoid colon. CT scan showed a tumor in the sigmoid colon, with bladder invasion. The para-aortic lymph node was partially swollen. We considered surgery to be high risk because of the patient's severe obesity. Therefore, we decided to examine the possibility of radical surgery followed by chemotherapy(mFOLFOX6/cetuximab)with weight reduction. Following this, the tumor had shrunk remarkably, and the patient's BMI decreased from 45 kg/m2 to 39 kg/m2. The visceral fat area was reduced from 298 cm2 to 199 cm2 at the umbilical level. We then performed a sigmoid colectomy with partial resection of the bladder. Thus, chemotherapy combined with weight loss enabled us to perform radical surgery safely for a locally advanced sigmoid colon cancer in a patient with severe obesity.

Combination of longitudinal pancreaticojejunostomy with coring-out of the pancreatic head (Frey procedure) and distal pancreatectomy for chronic pancreatitis.

PURPOSE: The Frey procedure is an effective surgery for chronic pancreatitis (CP) patients who have pancreatic head lesions with dilation of the main pancreatic duct. However, pancreatic tail lesions can cause relapsing pancreatitis after the procedure. Therefore, additional distal pancreatectomy (DP) might complement the therapeutic effect of the Frey procedure in controlling inflammation of the pancreatic tail. The Frey procedure with DP (Frey + DP) is indicated for inflammatory lesions in the pancreatic head and tail. In this study, we assessed the usefulness of Frey + DP using the retrospective clinical data of our cases. METHODS: The clinical outcomes were compared between CP patients who underwent the Frey procedure (N = 44) and Frey + DP (N = 13) from January 2005 to April 2016. RESULTS: Frey + DP showed similarly good therapeutic effects to the Frey procedure with regard to the postoperative stay, morbidity, mortality, pain relief and nutrition, although the Frey + DP had a longer operative time, more bleeding and higher incidence of diabetes mellitus than the Frey procedure because of the additional DP. One patient in the Frey group received additional DP because of recurrent pain due to the tail lesion. CONCLUSION: Frey + DP can be a promising treatment for CP patients with pancreatic head and tail lesions.

[A Case of Peritoneal Metastasis Resection from GIST of the Small Intestine with Focal Resistance Against Imatinib Mesylate].

A 69-year-old man was referred to our institute for the surgical resection of focal resistant peritoneal GIST during imatinib administration. He had been diagnosed with GIST of the small intestine with liver and peritoneal metastases, and imatinib treatment was initiated. Shortly after imatinib administration, the primary lesion perforated, and thus, partial resection of the small intestine was performed. Imatinib treatment was resumed after the first surgery, and he achieved partial response. However, computed tomography scans obtained 7 months after the first surgery showed focal progression, a peritoneal metastasis near the right kidney. Under the diagnosis of focally imatinib-resistant GIST, local resection of the metastatic tumor was performed. In this case, an exon 11 mutation of c-kit was noted initially. After the imatinib treatment, an additional point mutation was observed in exon 18 that caused resistance to imatinib. Therefore, imatinib treatment was reinitiated after the second surgery, and other metastases were well controlled. In case of GIST with multiple metastases, appropriate treatment should be selected based on the resistance of each lesion.

[A Case of Curatively Resected Rectal Cancer with Preservation of Urinary Function after Chemotherapy].

A55 -year-old man was diagnosed with rectal cancer invading the urinary bladder and swollen para-aortic lymph nodes. Since distant metastasis was indicated and total pelvic exenteration was required, 6 courses of chemotherapy with mFOLFOX6 plus panitumumab were performed. After the chemotherapy, the rectal cancer and para-aortic lymph nodes significantly decreased in size, and novel distant metastasis was not observed in CT scans. Therefore, the tumor was considered resectable, and operation was performed. Intraoperative frozen section analysis showed that the para-aortic lymph nodes and surgical margin of the urinary bladder were negative. Thus, low anterior resection of the rectum and partial resection of the urinary bladder were performed. R0 resection was pathologically achieved, and adjuvant chemotherapy with S-1 was administered for 6 months. The patient is alive without recurrence for 10 months. Upfront chemotherapy can be a strategy for advanced rectal cancer with urinary bladder invasion to avoid total pelvic exenteration.

Identification of Stem Cells in the Epithelium of the Stomach Corpus and Antrum of Mice.

BACKGROUND & AIMS: Little is known about the mechanisms of gastric carcinogenesis, partly because it has been a challenge to identify characterize gastric stem cells. Runx genes regulate development and their products are transcription factors associated with cancer development. A Runx1 enhancer element, eR1, is a marker of hematopoietic stem cells. We studied expression from eR1 in the stomach and the roles of gastric stem cells in gastric carcinogenesis in transgenic mice. METHODS: We used in situ hybridization and immunofluorescence analyses to study expression of Runx1 in gastric tissues from C57BL/6 (control) mice. We then created mice that expressed enhanced green fluorescent protein (EGFP) or CreERT2 under the control of eR1 (eR1-CreERT2;Rosa-Lox-Stop-Lox [LSL]-tdTomato, eR1-CreERT2;Rosa-LSL-EYFP mice). Gastric tissues were collected and lineage-tracing experiments were performed. Gastric organoids were cultured from eR1-CreERT2(5-2);Rosa-LSL-tdTomato mice and immunofluorescence analyses were performed. We investigated the effects of expressing oncogenic mutations in stem cells under control of eR1 using eR1-CreERT2;LSL-KrasG12D/+ mice; gastric tissues were collected and analyzed by histology and immunofluorescence. RESULTS: Most proliferation occurred in the isthmus; 86% of proliferating cells were RUNX1-positive and 76% were MUC5AC-positive. In eR1-EGFP mice, EGFP signals were detected mainly in the upper part of the gastric unit, and 83% of EGFP-positive cells were located in the isthmus/pit region. We found that eR1 marked undifferentiated stem cells in the isthmus and a smaller number of terminally differentiated chief cells at the base. eR1 also marked cells in the pyloric gland in the antrum. Lineage-tracing experiments demonstrated that stem cells in the isthmus and antrum continuously gave rise to mature cells to maintain the gastric unit. eR1-positive cells in the isthmus and pyloric gland generated organoid cultures in vitro. In eR1-CreERT2;LSL-Kras G12D/+ mice, MUC5AC-positive cells rapidly differentiated from stem cells in the isthmus, resulting in distinct metaplastic lesions similar to that observed in human gastric atrophy. CONCLUSIONS: Using lineage-tracing experiments in mice, we found that a Runx1 enhancer element, eR1, promotes its expression in the isthmus stem cells of stomach corpus as well as pyloric gland in the antrum. We were able to use eR1 to express oncogenic mutations in gastric stem cells, proving a new model for studies of gastric carcinogenesis.

[Two Cases of Locally Recurrent Rectal Cancer Successfully Treated by Carbon Ion Radiotherapy].

Case 1: A female patient in her 60s underwent laparoscopic intersphincteric resection for rectal cancer. After 42 months, the serum level of carcinoembryonic antigen(CEA)was elevated, and PET-CT showed a locally recurrent rectal cancer that increased FDG-uptake. Carbon ion radiotherapy(CIRT)(73.6 GyE/16 Fr)was performed. Serum CEA level and FDG-uptake were normalized. No regrowth of tumor has been found for 12 months. Case 2: A female patient in her 60s underwent abdominoperineal resection for rectal cancer. After 42 months, the serum level of CEA was elevated, and CT revealed a local recurrence of rectal cancer. Subsequently, the tumor was resected; however, resection margin was microscopically positive. Therefore, chemoradiotherapy(S-1, 60 Gy)was performed. At 31 months after local resection, a re-recurrent tumor was noted in her left ischium. Therefore, CIRT(70.4 GyE/16 Fr)was performed. Serum CEA level and FDG-uptake were normalized. No regrowth of tumor has been found for 24 months. CIRT is an effective therapy for locally recurrent rectal cancer.

[A Case of Laparoscopically Resected Giant Rectal Cancer Following Neoadjuvant Chemoradiotherapy].

A woman in her 40s who presented to a local hospital with bloody stool was referred to our hospital. Colonoscopy showed a rectal tumor, and histological examination showed moderately differentiated adenocarcinoma. CT and MRI revealed that the tumor was 65mm in diameter with no distant metastasis. After the construction of ileostomy, neoadjuvant chemoradiothera- py(NACRT: 45 Gy/25 Fr, S-1 80mg/m2)was performed. The tumor shrank remarkably, and then we performed laparoscopy- assisted low anterior resection. Pathological examination revealed complete disappearance of the cancer cells in the primary site and no appearance of cancer cells in all dissected lymph nodes. NACRT has been recently reported to provide pathological complete response, and these patients are supposed to have a good prognosis. In our case, NACRT enhanced the performance of laparoscopic curative resection while preserving anal function. NACRT should contribute to the curative resection while preserving anal function in patients with locally advanced rectal cancer.

[A Small Rectal Neuroendocrine Tumor of Less Than 5mm with Lymph Node Metastasis].

According to the treatment guideline for rectal neuroendocrine tumor(NET), tumor with a diameter ofC10mm should be resected endoscopically, while tumor with a diameter of>10mm should be resected surgically with lymph node dissection. We experienced a case of a rectal NET with a diameter of 5mm with lymph node metastasis. A 69-year-old man underwent colonoscopy for positive fecal occult blood test. The colonoscopy revealed a submucosal tumor(SMT)with a diameter of 5 mm in the lower rectum. An endoscopic mucosal resection(EMR)was performed after SMT was diagnosed as NET by biopsy. Histopathological findings were NET-G1, 4.5×2.5 mm, v(+), ly(+). Then, laparoscopically assisted rectal resection with D2 lymph node dissection was performed. In histopathological examination, no tumor residue was observed in the specimu; however, a regional lymph node metastasis was detected. Risk factors of lymph node metastasis with rectal NET are a diameter of>10 mm, recessed or ulcerated surface, and lymphovascular invasion. However, we have to keep in mind that lymph node metastasis may occur even in small rectal NET with a diameter of ≤10mm.