Treatment for appendicitis in cancer patients on chemotherapy: a retrospective cohort study

Purpose@#Whether to perform surgery or conservatively manage appendicitis in immunosuppressed patients is a concern for clinicians. This study aimed to compare the outcomes of these 2 treatment options for appendicitis in patients with cancer undergoing chemotherapy. @*Methods@#This retrospective study included 206 patients with cancer who were diagnosed with acute appendicitis between August 2001 and December 2021. Among them, patients who received chemotherapy within 1 month were divided into surgical and conservative groups. We evaluated the outcomes, including treatment success within 1 year, 1-year recurrence, and the number of days from the diagnosis of appendicitis to chemotherapy restart, between the 2 groups. @*Results@#Among the 206 patients with cancer who were diagnosed with acute appendicitis, 78 received chemotherapy within 1 month. The patients were divided into surgery (n = 63) and conservative (n = 15) groups. In the surgery group, the duration of antibiotic therapy (7.0 days vs. 16.0 days, P < 0.001) and length of hospital stay (8.0 days vs. 27.5 days, P = 0.002) were significantly shorter than conservative groups. The duration from the diagnosis of appendicitis to the restart of chemotherapy was shorter in the surgery group (20.8 ± 15.1 days vs. 35.2 ± 28.2 days, P = 0.028). The treatment success rate within 1 year was higher in the surgery group (100% vs. 33.3%, P < 0.001). @*Conclusion@#Surgical treatment showed a significantly higher success rate than conservative treatment for appendicitis in patients less than 1 month after chemotherapy. Further prospective studies will be needed to clinically determine treatment options.

Long-term clinical outcomes after high and low ligations with lymph node dissection around the root of the inferior mesenteric artery in patients with rectal cancer

Purpose@#This study aimed to evaluate the long-term clinical outcomes based on the ligation level of the inferior mesenteric artery (IMA) in patients with rectal cancer. @*Methods@#This was a retrospective analysis of a prospectively collected database that included all patients who underwent elective low anterior resection for rectal cancer between January 2013 and December 2019. The clinical outcomes included oncological outcomes, postoperative complications, and functional outcomes. The oncological outcomes included overall survival (OS) and relapse-free survival (RFS). The functional outcomes, including defecatory and urogenital functions, were analyzed using the Fecal Incontinence Severity Index, International Prostate Symptom Score, and International Index of Erectile Function questionnaires. @*Results@#In total, 545 patients were included in the analysis. Of these, 244 patients underwent high ligation (HL), whereas 301 underwent low ligation (LL). The tumor size was larger in the HL group than in the LL group. The number of harvested lymph nodes (LNs) was higher in the HL group than in the LL group. There were no significant differences in complication rates and recurrence patterns between the groups. There were no significant differences in 5-year RFS and OS between the groups. Cox regression analysis revealed that the ligation level (HL vs. LL) was not a significant risk factor for oncological outcomes. Regarding functional outcomes, the LL group showed a significant recovery in defecatory function 1 year postoperatively compared with the HL group. @*Conclusion@#LL with LNs dissection around the root of the IMA might not affect the oncologic outcomes comparing to HL; however, it has minimal benefit for defecatory function.

Colon cancer: the 2023 Korean clinical practice guidelines for diagnosis and treatment

Colorectal cancer is the third most common cancer in Korea and the third leading cause of death from cancer. Treatment outcomes for colon cancer are steadily improving due to national health screening programs with advances in diagnostic methods, surgical techniques, and therapeutic agents.. The Korea Colon Cancer Multidisciplinary (KCCM) Committee intends to provide professionals who treat colon cancer with the most up-to-date, evidence-based practice guidelines to improve outcomes and help them make decisions that reflect their patients’ values and preferences. These guidelines have been established by consensus reached by the KCCM Guideline Committee based on a systematic literature review and evidence synthesis and by considering the national health insurance system in real clinical practice settings. Each recommendation is presented with a recommendation strength and level of evidence based on the consensus of the committee.

Extracellular Mechanisms ofNeutrophils in Immune Cell Crosstalk

Neutrophils are professional phagocytes that provide defense against invading pathogens through phagocytosis, degranulation, generation of ROS, and the formation of neutrophil extracellular traps (NETs). Although long been considered as short-lived effector cells with limited biosynthetic activity, recent studies have revealed that neutrophils actively communicate with other immune cells. Neutrophils employ various types of soluble mediators, including granules, cytokines, and chemokines, for crosstalk with immune cells.Additionally, ROS and NETs, major arsenals of neutrophils, are utilized for intercellular communication. Furthermore, extracellular vesicles play a crucial role as mediators of neutrophil crosstalk. In this review, we highlight the extracellular mechanisms of neutrophils and their roles in crosstalk with other cells.

Stratification of rate of lymph node metastasis according to risk factors and oncologic outcomes in patients who underwent radical resection for rectal neuroendocrine tumors

Purpose@#Most predictive factors for lymph node metastasis in rectal neuroendocrine tumors (NETs) have been based on local and endoscopic resection. We aimed to evaluate the risk factors for lymph node metastasis in patients who underwent radical resection for rectal NETs and stratify the risk of lymph node metastasis. @*Methods@#Sixty-four patients who underwent radical resection for rectal NETs between January 2001 and January 2018 were included. We investigated the risk factors of lymph node metastasis using clinicopathologic data. We also performed a risk stratification for lymph node metastases using the number of previously known risk factors. For oncologic outcomes, the 5-year overall survival and recurrence-free survival were evaluated in both groups. @*Results@#Among the patients who underwent radical surgery, 32 (50.0%) had lymph node metastasis and 32 (50.0%) had non–lymph node metastasis. In the multivariable analysis, only the male sex was identified as a risk factor for lymph node metastasis (odds ratio, 3.695; 95% confidence interval, 1.128–12.105; P=0.031). When there were 2 or more known risk factors, the lymph node metastasis rate was significantly higher than when there were one or no risk factors (odds ratio, 3.667; 95% confidence interval, 1.023–13.143; P=0.046). There was also no statistical difference between the 2 groups in 5-year overall survival (P=0.431) and 5-year recurrence-free survival (P=0.144). @*Conclusion@#We found that the rate of lymph node metastasis increased significantly when the number of known risk factors is 2 or more.

Exfoliate cancer cell analysis in rectal cancer surgery: comparison of laparoscopic and transanal total mesorectal excision, a pilot study

Purpose@#Minimally invasive surgery (MIS) is currently the standard treatment for rectal cancer. However, its limitations include complications and incomplete total mesorectal resection (TME) due to anatomical features and technical difficulties. Transanal TME (TaTME) has been practiced since 2010 to improve this, but there is a risk of local recurrence and intra-abdominal contamination. We aimed to analyze samples obtained through lavage to compare laparoscopic TME (LapTME) and TaTME. @*Methods@#From June 2020 to January 2021, 20 patients with rectal cancer undergoing MIS were consecutively and prospectively recruited. Samples were collected at the start of surgery, immediately after TME, and after irrigation. The samples were analyzed for carcinoembryonic antigen (CEA) and cytokeratin 20 (CK20) through a quantitative real-time polymerase chain reaction. The primary outcome was to compare the detected amounts of CEA and CK20 immediately after TME between the surgical methods. @*Results@#Among the 20 patients, 13 underwent LapTME and 7 underwent TaTME. Tumor location was lower in TaTME (7.3 cm vs. 4.6 cm, P=0.012), and negative mesorectal fascia (MRF) was more in LapTME (76.9% vs. 28.6%, P=0.044). CEA and CK20 levels were high in 3 patients (42.9%) only in TaTME. There was 1 case of T4 with incomplete purse-string suture and 1 case of positive MRF with dissection failure. All patients were followed up for an average of 32.5 months without local recurrence. @*Conclusion@#CEA and CK20 levels were high only in TaTME and were related to tumor factors or intraoperative events. However, whether the detection amount is clinically related to local recurrence remains unclear.

Glycine induces enhancement of bactericidal activity of neutrophils

Severe bacterial infections are frequently accompanied by depressed neutrophil functions. Thus, agents that increase the microbicidal activity of neutrophils could add to a direct antimicrobial therapy. Lysophosphatidylcholine augments neutrophil bactericidal activity via the glycine (Gly)/glycine receptor (GlyR) α2/ TRPM2/p38 mitogen-activated protein kinase (MAPK) pathway. However, the direct effect of glycine on neutrophil bactericidal activity was not reported. In this study, the effect of glycine on neutrophil bactericidal activity was examined. Glycine augmented bactericidal activity of human neutrophils (EC50 = 238 μM) in a strychnine (a GlyR antagonist)-sensitive manner. Glycine augmented bacterial clearance in mice, which was also blocked by strychnine (0.4 mg/kg, s.c.). Glycine enhanced NADPH oxidase-mediated reactive oxygen species (ROS) production and TRPM2-mediated [Ca2+ ]i increase in neutrophils that had taken up E. coli. Glycine augmented Lucifer yellow uptake (fluid-phase pinocytosis) and azurophil granule-phagosome fusion in neutrophils that had taken up E. coli in an SB203580 (a p38 MAPK inhibitor)-sensitive manner. These findings indicate that glycine augments neutrophil microbicidal activity by enhancing azurophil granule-phagosome fusion via the GlyRα2/ROS/calcium/ p38 MAPK pathway. We suggest that glycine could be a useful agent for increasing neutrophil bacterial clearance.

Efficacy and Safety of Endoscopic Clipping for Acute Anastomotic Bleeding After Colorectal Surgery

Purpose@#Anastomotic bleeding after colorectal surgery is a rare, mostly self-limiting, postoperative complication that could lead to a life-threatening condition. Therefore, prompt management is required. This study aimed to evaluate the efficacy and safety of endoscopic clipping for acute anastomotic bleeding after colorectal surgery. @*Methods@#We retrospectively reviewed the data of patients pathologically diagnosed with colorectal cancer at National Cancer Center, Korea from January 2018 to November 2020, which presented with anastomotic bleeding within the first postoperative week and were endoscopically managed with clips. @*Results@#Nine patients had anastomotic bleeding, underwent endoscopic management, and, therefore, were included in this study. All patients underwent laparoscopic (low/ultralow) anterior resection with mechanical double-stapled anastomosis. Anastomotic bleeding was successfully managed through a colonoscopy with clips on the first trial in all patients. Hypovolemic shock occurred in one patient, following anastomotic breakdown. @*Conclusion@#Endoscopic clipping seems to be an effective and safe treatment for anastomotic bleeding with minimal physiologic stress, easy accessibility, and scarce postoperative complications. However, a surgical backup should always be considered for massive bleeding.

The risk of surgical site infection of oral sulfate tablet versus sodium picosulfate for bowel preparation in colorectal cancer surgery: a randomized clinical trial

Purpose@#Oral sulfate tablets are abundantly used for bowel preparation before colonoscopy. However, their efficiency and safety for bowel preparation before colorectal surgery remain ill-defined. Herein, we aimed to compare the surgical site infection rates and efficiency between oral sulfate tablets and sodium picosulfate. @*Methods@#We designed a prospective, randomized, phase 2 clinical trial. Patients with colorectal cancer aged 19–75 years who underwent elective bowel resection and anastomosis by minimally invasive surgery were administered oral sulfate tablets or sodium picosulfate. Eighty-three cases were analyzed from October 2020 to December 2021. Surgical site infection within 30 days after surgery was considered the primary endpoint. Postoperative morbidities, the degree of bowel cleansing, and tolerability were the secondary endpoints. @*Results@#Surgical site infection was detected in 1 patient (2.5%) in the oral sulfate tablet group and 2 patients (4.7%) in the sodium picosulfate group, indicating no significant difference between the 2 groups. Postoperative morbidity and the degree of bowel cleansing bore no statistically significant differences. Furthermore, none of the investigated tolerability criteria, namely bloating, pain, nausea, vomiting, and discomfort, differed significantly between the 2 groups. The patients’ willingness to reuse the drug was also not significantly different between the 2 groups. @*Conclusion@#Although we could not establish the noninferiority of oral sulfate tablets to sodium picosulfate, we found no evidence suggesting that oral sulfate tablets are less safe or tolerable than sodium picosulfate in preoperative bowel preparation.

Nucleocapsid and Spike Proteins of SARS-CoV-2 Drive Neutrophil Extracellular Trap Formation

Patients with severe coronavirus disease 2019 (COVID-19) demonstrate dysregulated immune responses including exacerbated neutrophil functions. Massive neutrophil infiltrations accompanying neutrophil extracellular trap (NET) formations are also observed in patients with severe COVID-19. However, the mechanism underlying severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-induced NET formation has not yet been elucidated.Here we show that 2 viral proteins encoded by SARS-CoV-2, the nucleocapsid protein and the whole spike protein, induce NET formation from neutrophils. NET formation was ROSindependent and was completely inhibited by the spleen tyrosine kinase inhibition. The inhibition of p38 MAPK, protein kinase C, and JNK signaling pathways also inhibited viral protein-induced NET formation. Our findings demonstrate one method by which SARSCoV-2 evades innate immunity and provide a potential target for therapeutics to treat patients with severe COVID-19.

Diverting ileostomy itself may not increase the rate of postoperative readmission related to dehydration after low anterior resection

Purpose@#This study was performed to evaluate the risk of readmission in the first year after low anterior resection (LAR) for patients with rectal cancer and to identify the contributing factors for readmission related to dehydration specifically. @*Methods@#This was a retrospective analysis of 570 patients who underwent LAR for rectal cancer at National Cancer Center, Republic of Korea. A diverting loop ileostomy was performed in 357 (62.6%) of these patients. Readmission was defined as an unplanned visit to the emergency room or admission to the ward. The reasons for readmission were reviewed and compared between the ileostomy (n = 357) and no-ileostomy (n = 213) groups. The risk factors for readmission and readmission due to dehydration were analyzed using multivariable logistic and Cox proportional hazard model. @*Results@#Dehydration was the most common cause of readmission in both groups (ileostomy group, 6.7%, and no-ileostomy group, 4.7%, P = 0.323). On multivariable analysis, risk factors for readmission were an estimated intraoperative blood loss of ≥400 mL (odds ratio [OR], 1.757; 95% confidence interval [CI], 1.058–2.918; P = 0.029), and postoperative chemotherapy (OR, 2.914; 95% CI, 1.824–4.653; P < 0.001). On multivariable analysis, postoperative chemotherapy, and not a diverting loop ileostomy, was an independent risk factor for dehydration-related readmission (OR, 5.102; 95% CI, 1.772–14.688; P = 0.003). @*Conclusion@#The most common cause of readmission after LAR for rectal cancer was dehydration, as reported previously. Postoperative chemotherapy, not the creation of a diverting ileostomy, was identified as the risk factor associated with readmission related to dehydration.

Diverting ileostomy itself may not increase the rate of postoperative readmission related to dehydration after low anterior resection

Purpose@#This study was performed to evaluate the risk of readmission in the first year after low anterior resection (LAR) for patients with rectal cancer and to identify the contributing factors for readmission related to dehydration specifically. @*Methods@#This was a retrospective analysis of 570 patients who underwent LAR for rectal cancer at National Cancer Center, Republic of Korea. A diverting loop ileostomy was performed in 357 (62.6%) of these patients. Readmission was defined as an unplanned visit to the emergency room or admission to the ward. The reasons for readmission were reviewed and compared between the ileostomy (n = 357) and no-ileostomy (n = 213) groups. The risk factors for readmission and readmission due to dehydration were analyzed using multivariable logistic and Cox proportional hazard model. @*Results@#Dehydration was the most common cause of readmission in both groups (ileostomy group, 6.7%, and no-ileostomy group, 4.7%, P = 0.323). On multivariable analysis, risk factors for readmission were an estimated intraoperative blood loss of ≥400 mL (odds ratio [OR], 1.757; 95% confidence interval [CI], 1.058–2.918; P = 0.029), and postoperative chemotherapy (OR, 2.914; 95% CI, 1.824–4.653; P < 0.001). On multivariable analysis, postoperative chemotherapy, and not a diverting loop ileostomy, was an independent risk factor for dehydration-related readmission (OR, 5.102; 95% CI, 1.772–14.688; P = 0.003). @*Conclusion@#The most common cause of readmission after LAR for rectal cancer was dehydration, as reported previously. Postoperative chemotherapy, not the creation of a diverting ileostomy, was identified as the risk factor associated with readmission related to dehydration.

Autophagy in neutrophils

Autophagy is a highly conserved intracellular degradation and energy-recycling mechanism that contributes to the maintenance of cellular homeostasis. Extensive researches over the past decades have defined the role of autophagy innate immune cells. In this review, we describe the current state of knowledge regarding the role of autophagy in neutrophil biology and a picture of molecular mechanism underlying autophagy in neutrophils. Neutrophils are professional phagocytes that comprise the first line of defense against pathogen. Autophagy machineries are highly conserved in neutrophils. Autophagy is not only involved in generalized function of neutrophils such as differentiation in bone marrow but also plays crucial role effector functions of neutrophils such as granule formation, degranulation, neutrophil extracellular traps release, cytokine production, bactericidal activity and controlling inflammation. This review outlines the current understanding of autophagy in neutrophils and provides insight towards identification of novel therapeutics targeting autophagy in neutrophils.

Current Understanding on the Metabolism of Neutrophils

Neutrophils are innate immune cells that constitute the first line of defense against invading pathogens. Due to this characteristic, they are exposed to diverse immunological environments wherein sources for nutrients are often limited. Recent advances in the field of immunometabolism revealed that neutrophils utilize diverse metabolic pathways in response to immunological challenges. In particular, neutrophils adopt specific metabolic pathways for modulating their effector functions in contrast to other immune cells, which undergo metabolic reprogramming to ensure differentiation into distinct cell subtypes. Therefore, neutrophils utilize different metabolic pathways not only to fulfill their energy requirements, but also to support specialized effector functions, such as neutrophil extracellular trap formation, ROS generation, chemotaxis, and degranulation. In this review, we discuss the basic metabolic pathways used by neutrophils and how these metabolic alterations play a critical role in their effector functions.

Current Understanding on the Metabolism of Neutrophils

Neutrophils are innate immune cells that constitute the first line of defense against invading pathogens. Due to this characteristic, they are exposed to diverse immunological environments wherein sources for nutrients are often limited. Recent advances in the field of immunometabolism revealed that neutrophils utilize diverse metabolic pathways in response to immunological challenges. In particular, neutrophils adopt specific metabolic pathways for modulating their effector functions in contrast to other immune cells, which undergo metabolic reprogramming to ensure differentiation into distinct cell subtypes. Therefore, neutrophils utilize different metabolic pathways not only to fulfill their energy requirements, but also to support specialized effector functions, such as neutrophil extracellular trap formation, ROS generation, chemotaxis, and degranulation. In this review, we discuss the basic metabolic pathways used by neutrophils and how these metabolic alterations play a critical role in their effector functions.

Small Bowel Perforation Associated With Gastrointestinal Graft-Versus-Host Disease and Cytomegalovirus Enteritis in a Patient With Leukemia: A Case Report With Literature Review

Gastrointestinal graft-versus-host disease (GVHD) is a common complication after hematopoietic stem cell transplantation. Concomitant cytomegalovirus (CMV) enteritis worsens the prognosis of this condition. We report a case of small bowel perforation associated with gastrointestinal GVHD and CMV enteritis in a patient with leukemia who was successfully treated surgically. A 39-year-old man presented with intestinal perforation necessitating emergency surgical intervention. He was diagnosed with T-cell acute lymphoblastic leukemia and developed severe gastrointestinal GVHD and CMV enteritis after hematopoietic stem cell transplantation. His terminal ileum showed a perforation with diffuse wall thinning, and petechiae were observed over long segments of the distal ileum and the proximal colon. Small bowel segmental resection and a subtotal colectomy with a double-barreled ileocolostomy were performed. The patient recovered uneventfully after the operation. Based on reports described in the literature, surgery plays a minor role in the management of gastrointestinal GVHD; however, timely surgical intervention could be effective in selected patients.

Cytoreductive Surgery and Hyperthermic Intraperitoneal Chemotherapy With Mitomycin C Used for Colorectal Peritoneal Carcinomatosis

Purpose@#This study aimed to assess the evaluation of clinical outcomes and consequences of complications after cytoreductive surgery (CRS) and hyperthermic intraperitoneal chemotherapy (HIPEC) for the peritoneal carcinomatosis (PC) from colorectal cancer. @*Methods@#A total 26 patients underwent CRS and HIPEC for PC from colorectal cancer between March 2009 and April 2018. All the patients underwent CRS with the purpose of complete or near-complete cytoreduction. Intraoperative HIPEC was performed simultaneously after the CRS. Mitomycin C was used as chemotherapeutic agent for HIPEC. @*Results@#Median disease-free survival was 27.8 months (range, 13.4–42.2 months). Median overall survival was 56.0 months (range, 28.6–83.5 months). The mean peritoneal cancer index (PCI) was 8.73 ± 5.54. The distributions thereof were as follows: PCI <10, 69.23%; PCI 10–19, 23.08%; and PCI ≥20, 7.69%. The completeness of cytoreduction was 96.2% of patients showed CC-0, with 3.8% achieved CC-1. The mean operation time was 8.5 hours, and the mean postoperative hospital stay was 21.6 days. The overall rate of early postoperative complications was 88.5%; the rate of late complications was 34.6%. In the early period, most complications were grades I–II complications (65.4%), compared to grades III–V (23.1%). All late complications, occurring in 7.7% of patients, were grades III–V. There was no treatment-related mortality. @*Conclusion@#Although the complication rate was approximately 88%, but the rate of severe complication rate was low. In selective patients with peritoneal recurrence, more aggressive strategies for management, such as CRS with HIPEC, were able to be considered under the acceptable general condition and life-expectancy.

The effect of curative resection on fecal microbiota in patients with colorectal cancer: a prospective pilot study

Purpose@#Although many studies have evaluated the association between intestinal microorganisms and the risk of colorectal cancer (CRC), only a few studies have investigated the changes in microorganisms following curative treatment for CRC. The current study analyzed changes in intestinal microbiota following curative surgery in CRC patients. @*Methods@#Stool samples were collected before and 6 months after surgery, from 11 patients with clinical stage III CRC, who underwent curative surgery between May 2017 and June 2017. Next, 16S rRNA gene sequencing was performed. Operational taxonomic units (OTUs) and alpha diversity were evaluated using the Shannon index. The bacterial compositions of the stools were analyzed according to taxonomic rank at genus and phylum levels. @*Results@#OTUs and alpha diversity were significantly decreased following surgery (P < 0.001 and P = 0.019, respectively). The compositions of several bacterial taxa changed after surgery. At genus level, proportions of pathogens such as Campylobacter, Fusobacterium, Haemophilus, Porphyromonas, and Prevotella, decreased after surgery (adjusted P < 0.05). At phylum level, the proportion of Fusobacteria decreased after surgery (adjusted P < 0.001). @*Conclusion@#Significant changes in intestinal microbial communities were noted following curative resection of CRC patients. Especially, decreases in pathogenic bacterial populations, such as Fusobacterium and Prevotella, which are known to be associated with CRC development, were detected even though OTUs and alpha diversity were decreased following curative resection. To determine and validate the clinical significance of these findings, large scale, prospective studies that include cancer prognoses are required.

The effect of curative resection on fecal microbiota in patients with colorectal cancer: a prospective pilot study

Purpose@#Although many studies have evaluated the association between intestinal microorganisms and the risk of colorectal cancer (CRC), only a few studies have investigated the changes in microorganisms following curative treatment for CRC. The current study analyzed changes in intestinal microbiota following curative surgery in CRC patients. @*Methods@#Stool samples were collected before and 6 months after surgery, from 11 patients with clinical stage III CRC, who underwent curative surgery between May 2017 and June 2017. Next, 16S rRNA gene sequencing was performed. Operational taxonomic units (OTUs) and alpha diversity were evaluated using the Shannon index. The bacterial compositions of the stools were analyzed according to taxonomic rank at genus and phylum levels. @*Results@#OTUs and alpha diversity were significantly decreased following surgery (P < 0.001 and P = 0.019, respectively). The compositions of several bacterial taxa changed after surgery. At genus level, proportions of pathogens such as Campylobacter, Fusobacterium, Haemophilus, Porphyromonas, and Prevotella, decreased after surgery (adjusted P < 0.05). At phylum level, the proportion of Fusobacteria decreased after surgery (adjusted P < 0.001). @*Conclusion@#Significant changes in intestinal microbial communities were noted following curative resection of CRC patients. Especially, decreases in pathogenic bacterial populations, such as Fusobacterium and Prevotella, which are known to be associated with CRC development, were detected even though OTUs and alpha diversity were decreased following curative resection. To determine and validate the clinical significance of these findings, large scale, prospective studies that include cancer prognoses are required.

Characteristics of minute T1 colorectal cancer in relevance to pathology and treatment

Purpose@#Minute T1 colorectal cancer (CRC) lesions (≤5 mm) are rare; however, little is known about their characteristics and aggressiveness. In this study, we evaluated the characteristics of minute T1 CRC in relevance to pathology and treatment. @*Methods@#This retrospective study included 849 patients with T1 CRC endoscopically or surgically treated between January 2001 and December 2016. The patients were stratified into 4 groups according to tumor size; minute group (≤5 mm), small group (6–10 mm), medium group (11–20 mm), and large group (≥21 mm). Clinicopathological variables were evaluated with respect to tumor size. @*Results@#The incidence of the minute T1 CRC was 2.4% (20 of 849). Minute T1 CRC was significantly associated with flat type (minute, 25%; small, 12.6%; medium, 8.8%; large, 12.6%; P = 0.016), right-sided cancer (30%, 15.4%, 15.4%, 15.1%, P = 0.002) and the absence of background adenoma (BGA) (50%, 40.7%, 32.8%, 18.1%, P < 0.001). In patients who underwent surgery, lymph node metastasis (LNM) was significantly higher in the minute group (36.4%, 15.9%, 15.7%, 9.2%, P = 0.029). @*Conclusion@#Minute T1 CRC is significantly associated with flat type, right-sided cancers, as well as with the absence of BGA and LNM. These results suggested the minute T1 CRC lesions are often aggressive and are likely to be missed during colonoscopy.