Anatomy of muscle connections in the male urethra and anorectal canal

OBJECTIVES

To elucidate the male urethral muscular structure and its relationship with the anorectal canal muscles, as establishing an anatomical foundation for urethral function will contribute to the prevention, diagnosis, and treatment of urinary incontinence.

METHODS

Eight male cadavers were used. Using a multifaceted approach, we performed macroscopic anatomical examination, histological analysis of wide-range serial sectioning and immunostaining, and three-dimensional (3D) reconstruction from histological sections. In the macroscopic anatomical examination, pelvic halves were meticulously dissected in layers from the medial aspect. In the histological analysis, the tissue, including the urethra and anorectal canal, was serially sectioned in the horizontal plane. The muscular structures were reconstructed and visualised in 3D.

RESULTS

The membranous portion of the urethra had three muscle layers: the longitudinal and circular muscles (smooth muscle) and the external urethral sphincter (skeletal muscle). The circular muscle was connected posteriorly to the longitudinal rectal muscle. The external urethral sphincter had a horseshoe shape, with its posterior ends continuing to the external anal sphincter, forming a 3D ring-like sphincter.

CONCLUSION

This study revealed skeletal and smooth muscle connections between the male urethra and anorectal canal, enabling urethral compression and closure. These anatomical muscle connections suggest a functional linkage between them.

Gross morphologic features of surgical specimen in rectal cancer patients with pathological complete response following neoadjuvant chemoradiotherapy: A cross-sectional study

BACKGROUND

pathological complete response (pCR) is achieved in 10%-30% of rectal cancer patients following neoadjuvant chemoradiotherapy and surgery. Residual mucosal abnormalities, which make patients ineligible for nonoperative management, may not be an accurate indicator of the pCR. The purpose of this study was to report the gross findings of rectal cancer patients with pathological complete responses.

METHODS

This study was conducted at Tehran University of Medical Sciences, Tehran, Iran. A total of 130 patients with rectal adenocarcinoma, treated by neoadjuvant chemoradiotherapy, followed by surgical resection between March 2007, and March 2017, with a surgical pathology report of pCR, were included. Patients' demographics and pretreatment tumor characteristics were collected from the medical records. Data regarding residual mucosal abnormalities were extracted from postoperative surgical pathology reports. Abnormal findings were reported as "ulcer" or " non-ulcerative lesion".

RESULTS

One hundred and fifteen patients (88.5%; 95% CI: 81.7%-93.4%) had at least one abnormal finding in the gross examination, including ulcer or non-ulcerative lesion (any mucosal abnormalities other than ulcers, including polyps, telangiectasia, etc.). Patients with higher-stage tumors had a higher chance of having an ulcerative lesion (p = 0.05). Younger patients tended to have deeper layers of involvement (p = 0.013). Patients with different gross findings were not significantly different regarding baseline characteristics, except for the pretreatment stage, where patients with a higher stage had higher odds of having ulcerative lesions.

CONCLUSIONS

Most rectal cancer patients achieving a pCR exhibit abnormalities on gross examination. The higher pretreatment stages were significantly associated with gross abnormalities especially ulcers.

Colorectal Sarcomatoid Carcinoma: 30-Year Experience

Background: Primary colorectal sarcomatoid carcinoma is a rare and aggressive malignant neoplasm that displays mixed epithelial and mesenchymal differentiation, with uncertain histogenesis. First described in 1986, there is a paucity of literature related to this condition and there are no evidence-based treatment guidelines. The aim of our study is to present our 30-year experience with primary colorectal sarcomatoid carcinoma. Methods: Retrospective single-center analysis of all patients treated for primary colorectal sarcomatoid carcinoma from 1992 to 2022. The primary outcome was response to treatment strategy and overall survival. Results: A total of six cases met eligibility criteria. Three were male (50%) with a mean age at diagnosis of 59 years (range, 49-72). Four neoplasms were located in the rectum (66%) and two in the colon. Mean tumor size at diagnosis was 4.8 cm (range, 2.8-7.0). Three patients were treated endoscopically and three underwent oncologic surgical resection. Five experienced recurrence and one expired from other comorbidities. The mean survival among those with colonic and rectal sarcomatoid carcinoma was 7 months (range, 3-11) and 39 months (range, 9-60), respectively. Discussion: Primary colorectal sarcomatoid carcinoma is a rare malignant tumor with poor prognosis. Treatment modalities have not been standardized and despite multimodal therapy, disease recurrence and/or metastasis is likely to occur. Further studies are necessary to determine optimal treatment to improve outcomes.

Rectal volume is correlated with interfractional positional shifts of the prostate gland in dogs receiving radiation therapy

Variability in prostate gland positioning during RT for prostate tumors is a recognized challenge in both human and veterinary oncology. This retrospective study investigates the interfractional variability in prostate gland positioning in relation to rectal and bladder volumes in dogs undergoing radiation therapy (RT) for prostate tumors. The study tracked 10 dogs undergoing five RT sessions from February 2016 to November 2021, delivering a total of 25 Gy each. Each dog underwent CT scans for treatment simulation, and cone-beam CT (CBCT) images were acquired before each RT. The focus was to analyze the positional shifts of the prostate gland concerning the volumes of the rectum and urinary bladder. The pelvic bones were used as the point of reference. The rectal and bladder volumes were measured before each RT, and shifts in the prostate gland position were calculated by comparing coordinates from planning CT and treatment session images. Findings revealed significant correlations between prostate positional shifts in the dorsal-ventral (repeated measures correlation coefficient of -0.58 [range 00.75-00.33]; P < .001) and cranial-caudal directions (repeated measures correlation coefficient [95%CI] 0.56 [range 0.31-0.74]; P < .001) and rectal volume, while no significant relationship was observed with bladder volume. Shifts in the lateral direction were not correlated with either organ's volume. This study highlights the importance of considering rectal volume in canine prostate tumor RT to minimize positional uncertainties. Maintaining consistent rectal volume may enhance the precision of prostate targeting, potentially influencing the safety of RT.

Gastrointestinal Tract Granular Cell Tumor in the Pediatric Population: A Multicenter Experience

BACKGROUND

Pediatric granular cell tumors (GCT) involving the gastrointestinal tract (GIT) are rare with limited case report/series reported to date.

METHODS

Multicenter retrospective study of pediatric GIT GCT.

RESULTS

A total of 10 cases were included in the study with a median age of 13.5 years (range: 7-18 years) and were predominantly female patients (60%). In half of the patients no significant medical history was present with the remaining 5 having Crohn disease (10%), eosinophilic esophagitis (EoE) (10%), Crohn disease and EoE (10%), growth hormone deficiency (10%), and aplasia cutis congenita (10%). The GCT median size was 1.3 cm (range: 1-1.6 cm) and were more commonly located in the esophagus (70%) followed by the stomach (20%) and rectum (10%). Most of the cases showed round/polygonal tumor cells with abundant granular cytoplasm, and none of the cases had nuclear atypia, increased mitotic activity, or tumor cell necrosis. None of our cases received specific therapy for GCT other than clinical follow-up, and none of the patients had evidence of local recurrence or metastatic disease.

CONCLUSION

We present our multicenter experience with GIT GCT, all cases had a benign course. Interestingly, 4 of the esophageal GCT cases (including 2 patients with EoE) showed an eosinophil-rich esophagitis in the underlying mucosa.

Retroperitoneoscopy of the presacral space in horses: Surgical access and anatomy

BACKGROUND

Surgical approaches to the equine rectum and perirectal area are described in the literature. However, surgeries in this region can be challenging.

OBJECTIVE

To describe the surgical anatomy of the presacral space and to evaluate its access using a retroperitoneoscopic approach.

STUDY DESIGN

Ex vivo experiment.

METHODS

Preliminary dissections were performed in two cadavers to define the boundaries of the presacral space and to determine portal locations for the surgical approach. After that, nine cadavers were used for experimental presacral retroperitoneoscopic procedure in a standing position. Following retroperitoneoscopy, cadavers were dissected to confirm the anatomical structures observed during the endoscopic procedures, to control the location of each portal and to record iatrogenic trauma.

RESULTS

The presacral space was bordered by the vertebral column from the ventral aspect of lumbosacral promontorium to the first coccygeal vertebra dorsally and by the presacral fascia and peritoneum ventrally. Lateral limits were composed of the sacrosciatic ligament and transversalis fascia. Cranial and caudal borders were composed of the peritoneum and coccygeal and levator ani muscles respectively. Retroperitoneoscopic portals were placed between the external anal sphincter and semimembranosus muscles and between the base of the tail and the external anal sphincter muscle through the anococcygeal fascia to enter the space by its caudal border. The retroperitoneal space was reached in all cases and the dorsal and lateral aspects of the rectum were visualised after creation of a working space.

MAIN LIMITATIONS

Use of cadaver specimens do not permit to evaluate the tolerance in living animals and the surgical complications such as rectal damage, haemorrhage and infection.

CONCLUSION

This study provides an anatomical description and surgical access of the presacral space with a minimal invasive approach. Retroperitoneoscopy allows access to the rectum and the dorsal aspect of the pelvis.

Preoperative beta blockers and other drugs in relation to anastomotic leakage after anterior resection for rectal cancer

AIM

Previous research has indicated that preoperative beta blocker therapy is associated with a decreased risk of complications after surgery for rectal cancer. This is thought to arise because of the anti-inflammatory activity of the drug. These results need to be reproduced and analyses extended to other drugs with such properties, as this information might be useful in clinical decision-making. The main aim of this work was to replicate previous findings of beta blocker use as a prognostic marker for postoperative leakage. We also investigated whether drug exposure might induce anastomotic leaks.

METHOD

This is a retrospective multicentre cohort study, comprising 1126 patients who underwent anterior resection for rectal cancer between 2014 and 2018. The use of any preoperative beta blocker was treated as the primary exposure, while anastomotic leakage within 12 months of surgery was the outcome. Secondary exposures comprised angiotensin-converting enzyme inhibitors/angiotensin receptor blockers, statins and metformin. Using multivariable regression, we performed a replication analysis with a predictive aim for beta blockers only, while adjustment for confounding was done in more causally oriented analyses for all drugs. We estimated incidence rate ratio (IRR) and relative risk (RR) with 95% confidence intervals (CIs).

RESULTS

Anastomotic leakage occurred in 20.6% of patients. Preoperative beta blockers were used by 22.7% of the cohort, while the leak distribution was almost identical between exposure groups. In the main replication analysis, no association could be detected (IRR 0.95, 95% CI 0.68-1.33). In the causally oriented analyses, only metformin affected the risk of leakage (RR 1.59, 95% Cl 1.31-1.92).

CONCLUSION

While previous research has suggested that preoperative beta blocker use could be prognostic of anastomotic leakage, this study could not detect any such association. On the contrary, our results indicate that preoperative beta blocker use neither predicts nor causes anastomotic leakage after anterior resection for rectal cancer.

EBV-Positive Intravascular Large B-Cell Lymphoma of the Small Intestine: A Case Report and Literature Review

Intravascular large B-cell lymphoma (IVLBCL) is a rare lymphoma that affects the brain, skin, and bone marrow. We describe the case of a 75-year-old man who was admitted to the hospital after 4 h of stomach aches. A thorough physical examination indicated stomach discomfort and skin discoloration. Laboratory tests revealed thrombocytopenia and elevated lactate dehydrogenase levels. A computed tomography scan of the abdomen revealed that the small intestine wall was thickened, edematous, and necrotic. The necrotic small bowel was surgically removed, revealing many little round, homogenous, and unusual cells in the mesenteric vein. In-situ hybridization revealed that these cells were positive for PAX5, CD20, CD79a, CD10, and BCL2, as well as Epstein-Barr virus-encoded small RNA. After 1 week of hospitalization without treatment, the patient was diagnosed with IVLBCL and died of multiple organ dysfunction syndrome. IVLBCL is a rare illness that affects the small intestine and possibly the gastrointestinal system. It has an insidious start, a fast development, and a dismal prognosis. Knowing its clinicopathologic traits helps in understanding the illness, making an early diagnosis, and preventing rapid worsening.

Comprehensive CT Imaging Analysis of Primary Colorectal Squamous Cell Carcinoma: A Retrospective Study

The aim of this study was to evaluate the findings of CT scans in patients with pathologically confirmed primary colorectal squamous-cell carcinoma (SCC). The clinical presentation and CT findings in eight patients with pathologically confirmed primary colorectal squamous-cell carcinoma were retrospectively reviewed by two gastrointestinal radiologists. Hematochezia was the most common symptom (n = 5). The tumors were located in the rectum (n = 7) and sigmoid colon (n = 1). The tumors showed circumferential wall thickening (n = 4), bulky mass (n = 3), or eccentric wall thickening (n = 1). The mean maximal wall thickness of the involved segment was 29.1 mm ± 13.4 mm. The degree of tumoral enhancement observed via CT was well enhanced (n = 4) or moderately enhanced (n = 4). Necrosis within the tumor was found in five patients. The mean total number of metastatic lymph nodes was 3.1 ± 3.3, and the mean short diameter of the largest metastatic lymph node was 16.6 ± 5.7 mm. Necrosis within the metastatic node was observed in six patients. Invasions to adjacent organs were identified in five patients (62.5%). Distant metastasis was detected in only one patient. In summary, primary SCCs that arise from the colorectum commonly present as marked invasive wall thickening or a bulky mass with heterogeneous well-defined enhancement, internal necrosis, and large metastatic lymphadenopathies.

Evaluation of association between center colorectal neuroendocrine neoplasm volume and survival among patients with colorectal neuroendocrine carcinoma

BACKGROUND

Although correlation between center volume and survival has been reported for several complex cancers, it remains unknown if this is true for colorectal neuroendocrine carcinomas (CRNECs). We hypothesized that higher center annual volume of colorectal neuroendocrine neoplasm resections would be associated with overall survival (OS) for patients with CRNECs.

METHODS

Patients in the National Cancer Database diagnosed with stages I-III CRNEC between 2006 and 2018 and who underwent surgical resection were identified. The mean annual colorectal neuroendocrine neoplasm resection volume threshold associated with significantly worse mortality hazard was determined using restricted cubic splines. Kaplan-Meier (KM) method was used to compare OS, while Cox proportional hazards model was used for multivariable analysis.

RESULTS

There were 694 patients with CRNEC who met inclusion criteria across 1229 centers. Based on the cubic spline, centers treating fewer than one colorectal neuroendocrine neoplasm patient every 3 years on average had worse outcomes. Centers below this threshold were classified as low-volume (LV) centers corresponding with 42% of centers and about 15% of the patient cohort. In unadjusted survival analysis, LV patients had a median OS of 14 months (95% confidence interval [CI]: 10-19) while those treated at HV centers had a median OS of 33 months (95% CI: 25-49). In multivariable analysis, resection at a LV center was associated with increased risk of mortality (1.42 [95% CI: 1.01-2.00], p = 0.04).

CONCLUSION

CRNEC patients have a dire prognosis; however, treatment at an HV center may be associated with decreased risk of mortality.

Clinical Outcome of Patients with Gastric, Duodenal, or Rectal Neuroendocrine Tumors after Incomplete Endoscopic Resection

Objectives: Our aim was to investigate the clinical outcome of patients with well-differentiated gastric, duodenal, and rectal neuroendocrine tumors after treatment with incomplete endoscopic resection due to the finding of microscopic positive resection margins (R1). Methods: This is a retrospective analysis of consecutive patients with type 1 gastric, non-ampullary non-functioning duodenal, or rectal neuroendocrine neoplasms with positive R1 margins after endoscopic resection. The rate of tumor recurrence and progression-free survival were considered to be the study's main endpoints. Statistical analysis was performed using MedCalc® v.17 software and a p-value of <0.05 was considered significant. A Cox proportional-hazard regression was performed to identify risk factors for disease recurrence/progression. Results: After evaluating 110 patients, a total of 58 patients were included in the final analysis (15 gastric NENs, 12 duodenal NENs, and 31 rectal NENs). After evidence of endoscopic R1 resection had been gathered, 26 patients (44.8%) underwent an endoscopic/surgical extension of the previous resection. Tumor progression (all local recurrences) occurred in five out of fifty-eight patients (8.6%) with a median PFS of 36 months. There were no tumor-related deaths. G2 grading and the gastric primary tumor site were the only features significantly associated with the risk of recurrence of the disease (HR: 11.97 [95% CI: 1.22-116.99], HR: 12.54 [95% CI: 1.28-122.24], respectively). Conclusions: Tumor progression rarely occurs in patients with microscopic positive margin excision (R1) after endoscopic resection and does not seem to affect patients' clinical outcomes.

Traction Devices May Not Affect the Vertical Margin Distance in the Endoscopic Submucosal Dissection of Rectal Neuroendocrine Tumors

Introduction The usefulness of traction devices (TDs) in endoscopic submucosal dissection (ESD) for rectal neuroendocrine tumors (NETs) has not been reported. The aim of this study was to investigate the impact of using a TD on the vertical margin (VM) distance in the ESD of rectal NETs. Methods In this single-center, retrospective study, we included patients with rectal NETs who were treated with ESD during 2013-2023. They were divided into TD and non-TD groups. One pathologist remeasured the VM distance (primary outcome) and the depth of submucosal invasion (SM depth). Secondary outcomes were margins, resection time, delayed bleeding, and perforation. First, we performed propensity score matching (PSM) to assess the usefulness of TD for VM distance. Then, we used multiple regression analysis to identify factors affecting the VM distance. Results The TD and non-TD groups comprised 24 and 117 lesions, respectively. Patients in the TD group were significantly younger than those in the non-TD group (P = 0.003). In the TD and non-TD groups, the VM distance was 150 μm and 100 μm, respectively (P = 0.70). Only resection time significantly differed between groups, shorter in the TD group (P = 0.005). Twenty-two cases in each group were matched after PSM, yielding no significant differences in VM distance. The use of a TD was not an independent predictor of VM distance (P = 0.65), but age (P < 0.001) and SM depth (P = 0.003) were. Conclusion Using a TD does not seem to affect the VM distance in ESD for rectal NETs.

Retrorectal Hernia: A Rare Cause of Constipation Diagnosed on Magnetic Resonance (MR) Defecography

Retrorectal herniation of the sigmoid colon is a rare condition characterized by the protrusion of a segment of the colon into the pre-sacral space and posterior to the rectum. This herniation occurs through a defect in the peritoneum, which may have developed secondary to congenital mechanisms, surgery, trauma, or inflammatory processes. Here, a case of retrorectal herniation of the sigmoid colon in an elderly female patient presenting with constipation is reported, with a review of the literature.

Robotic surgery for deep-infiltrating endometriosis: is it time to take a step forward?

Endometriosis is a chronic debilitating disease that affects nearly 10% of women of the reproductive age. Although the treatment modalities of endometriosis are numerous, surgical excision of the endometriotic implants and nodules remains the sole cytoreductive approach. Laparoscopic excision of endometriosis was proven to be beneficial in improving the postoperative pain and fertility. Moreover, it was also proved to be safe and efficient in treating the visceral localization of deep endometriosis, such as urinary and colorectal endometriosis. More recently, robotic-assisted surgery gained attention in the field of endometriosis surgery. Although the robotic technology provides a 3D vision of the surgical field and 7-degree of freedom motion, the safety, efficacy, and cost-effectiveness of this approach are yet to be determined. With this paper, we aim to review the available evidence regarding the role of robotic surgery in the management of endometriosis along with the current practices in the field.

Nodular hyperplasia of lymphoglandular complexes in dogs: A potential diagnostic pitfall for rectal masses

Lymphoglandular complexes are components of the gut-associated lymphoid tissue that are characterized by submucosal lymphoid aggregates invested by projections of mucosal epithelium. Reports of pathology involving these structures are rare in both human and veterinary literature. Here, the authors report 2 cases of rectal masses excised from dogs following a period of tenesmus and hematochezia. In both animals, the masses were composed of lymphoid tissue closely encompassing tubuloacinar structures. Immunohistochemistry and polymerase chain reaction antigen receptor rearrangement testing demonstrated that the lymphoid population was polyclonal, comprising T and B cells arranged in loosely follicular aggregates centered on the epithelial foci. In light of these findings, a diagnosis of lymphoglandular complex nodular hyperplasia was reported. To the authors' knowledge, this is the first report of this condition in dogs.

A Novel Use of a Schanz Pin-Rectal Foreign Body Extraction: A Case Report

Introduction

Retained rectal foreign bodies (RFBs) can be difficult to extract, forcing the surgeon to get creative. This is the first case report utilizing orthopedic drilling and joystick manipulation techniques for foreign body extraction.

Case Report

A 63-year-old male presented to the emergency department with a pool ball in his rectum for two days. Extraction attempts under anesthesia both transanally and through a low midline laparotomy were unsuccessful due to the patient's pelvic anatomy. Orthopedic surgery was consulted to see if any manipulation or resection of the pelvis might aid in extraction. Ultimately, a Schanz pin was drilled retrogradely from the rectum into the pool ball and successfully manipulated the pool ball out of the patient.

Conclusion

Techniques such as drilling and joystick manipulation are common in orthopedic surgery but rarely used in other surgical fields. This case presented a novel use of a Schanz pin in RFB extraction. Application of orthopedic surgical technique in a colorectal surgery in this case saved the patient from more invasive interventions such as pubic symphysiotomy or ischial tuberosity resection.

Analysis of cell populations in the normal rhesus macaque (Macaca mulatta) lower intestinal tract and diagnostic thresholds for chronic enterocolitis

Rhesus macaques (Macaca mulatta) are used extensively in biomedical research, often with a focus on the gastrointestinal tract, and yet a full characterization of their normal resident intestinal cell populations has not been published. In addition, chronic enterocolitis (CE), also known as idiopathic chronic diarrhea, affects up to 25% of colony-housed rhesus macaques, often requiring euthanasia for welfare concerns and severely limiting their value as a breeding animal or research subject. We aimed to characterize subjective and objective variables in sections of the ileum, cecum, colon, and rectum in 16 healthy rhesus macaques and compare these results with a cohort of 37 animals euthanized for CE to produce relevant diagnostic thresholds and to improve case definitions for future studies. We found neutrophils to be an infrequent but expected component of the large intestinal leukocyte population. Animals with CE had significantly increased total leukocyte populations between crypts in the cecum, colon, and rectum; variable increases in specific cell populations across all levels of the distal intestinal tract; and significantly increased intraepithelial CD3+ T cells in the colon and rectum. Concentrations of enteroendocrine cells, enterochromaffin cells, and intestinal mast cells were not significantly different between healthy and affected individuals. This study characterizes individual leukocyte populations in the rhesus macaque lower intestinal tract, is the first to evaluate rhesus macaque intestinal mast cells, and provides key diagnostic thresholds for evaluating animals with potential CE.

Submucosal Lipoma in the Rectum Found Incidentally During Colonoscopy Screening: A Case Report

Gastrointestinal (GI) tract lipomas are a benign entity of GI tumors. In this case report, we present a 53-year-old patient who was found to have a rectal lipoma incidentally in an asymptomatic middle-aged female during a routine colonoscopy screening. The tumor was excised during colonoscopy and sent for histopathology, which confirmed the diagnosis. We also provide a literature review of GI lipomas, focusing on their occurrence in the rectum.

RAS mutation status in combination with the JSHBPS nomogram may be useful for preoperative identification of colorectal liver metastases with high risk of recurrence and mortality after hepatectomy

PURPOSE

To investigate the prognostic impact of RAS mutations on the Japanese Society of Hepatobiliary and Pancreatic Surgeons (JSHBPS) nomogram score in patients with colorectal cancer liver metastasis (CRLM) following hepatectomy.

METHODS

We included 218 consecutive patients undergoing hepatectomy for CRLM between 2004 and 2020. The JSHBPS nomogram score was calculated using six preoperative clinical factors. The score ranged from 0 to 25, and higher scores indicated greater tumor burden. Associations of RAS mutations with disease-free survival (DFS) and overall survival (OS) by the JSHBPS nomogram score were examined. Multivariable Cox proportional hazard regression models were used to estimate adjusted hazard ratios (HRs) and confidence intervals (CIs).

RESULTS

RAS mutations were detected in 72 (33%) of the 218 patients. Multivariate analyses revealed that RAS mutations were independently associated with poor DFS (HR, 1.93; 95% CI: 1.20-3.10; p = .007) and OS (HR, 2.65; 95% CI: 1.59-4.71; p = .001) compared with wild-type RAS with JSHBPS nomogram scores ≤ 10. However, in patients with scores ≥ 11, the association of RAS mutations with DFS or OS was not statistically significant (p > .08).

CONCLUSION

RAS mutation status in combination with the JSHBPS nomogram may be useful for preoperatively identifying CRLM with high risk of recurrence and mortality after hepatectomy.

Tumor-associated microbiome features of metastatic colorectal cancer and clinical implications

Background

Colon microbiome composition contributes to the pathogenesis of colorectal cancer (CRC) and prognosis. We analyzed 16S rRNA sequencing data from tumor samples of patients with metastatic CRC and determined the clinical implications.

Materials and methods

We enrolled 133 patients with metastatic CRC at St. Vincent Hospital in Korea. The V3-V4 regions of the 16S rRNA gene from the tumor DNA were amplified, sequenced on an Illumina MiSeq, and analyzed using the DADA2 package.

Results

After excluding samples that retained <5% of the total reads after merging, 120 samples were analyzed. The median age of patients was 63 years (range, 34-82 years), and 76 patients (63.3%) were male. The primary cancer sites were the right colon (27.5%), left colon (30.8%), and rectum (41.7%). All subjects received 5-fluouracil-based systemic chemotherapy. After removing genera with <1% of the total reads in each patient, 523 genera were identified. Rectal origin, high CEA level (≥10 ng/mL), and presence of lung metastasis showed higher richness. Survival analysis revealed that the presence of Prevotella (p = 0.052), Fusobacterium (p = 0.002), Selenomonas (p<0.001), Fretibacterium (p = 0.001), Porphyromonas (p = 0.007), Peptostreptococcus (p = 0.002), and Leptotrichia (p = 0.003) were associated with short overall survival (OS, <24 months), while the presence of Sphingomonas was associated with long OS (p = 0.070). From the multivariate analysis, the presence of Selenomonas (hazard ratio [HR], 6.35; 95% confidence interval [CI], 2.38-16.97; p<0.001) was associated with poor prognosis along with high CEA level.

Conclusion

Tumor microbiome features may be useful prognostic biomarkers for metastatic CRC.

Analysis of the Genetic Characteristics and Metastatic Pathways of G1 and G2 Colorectal Neuroendocrine Neoplasms

Objective

G1 and G2 colorectal neuroendocrine neoplasms (NENs) are a group of rare and indolent diseases. We aimed to delineate their genetic characteristics and explore their metastatic mechanisms.

Methods

We used next-generation sequencing technology for targeted sequencing for 54 patients with G1 and G2 colorectal NENs. We delineated their genetic features and compared the genetic characteristics between metastatic NENs and nonmetastatic NENs. Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis was utilized to explore their abnormal pathways and study their potential metastatic mechanisms.

Results

We collected 23 metastatic NENs and 31 nonmetastatic NENs. In the whole cohort, the common mutated genes were NCOR2, BRD4, MDC1, ARID1A, AXIN2, etc. The common copy number variations (CNVs) included amplification of HIST1H3D, amplification of HIST1H3E, and loss of PTEN. The KEGG enrichment analysis revealed that PI3K-Akt, MAPK, and Rap1 were the major abnormal pathways. There were significantly different genetic features between metastatic NENs and nonmetastatic NENs. The metastatic NENs shared only 47 (22.5%) mutated genes and 6 (13.3%) CNVs with nonmetastatic NENs. NCOR2, BRD4, CDKN1B, CYP3A5, and EIF1AX were the commonly mutated genes in metastatic NENs, while NCOR2, MDC1, AXIN2, PIK3C2G, and PTPRT were the commonly mutated genes in nonmetastatic NENs. Metastatic NENs presented a significantly higher proportion of abnormal pathways of cell senescence (56.5% vs 25.8%, P = .022) and lysine degradation (43.5% vs 16.1%, P = .027) than nonmetastatic NENs.

Conclusion

G1 and G2 colorectal NENs are a group of heterogeneous diseases that might obtain an increased invasive ability through aberrant cell senescence and lysine degradation pathways.

An Unusual Case of Gastric Heterotopia Presenting as Rectal Prolapse

Heterotopic gastric mucosa (HGM) involving the rectum is an uncommon finding. It is especially rare in young children. Rectal prolapse is an uncommon presentation of HGM. We report a case of HGM in the rectum of a 2-year-old previously healthy girl, who presented with rectal prolapse and painless bleeding. Endoscopic mucosal resection was performed to completely resect the lesion after the patient failed to respond to proton pump inhibitors. This case underscores the importance of considering HGM involving the rectum as a cause of rectal prolapse in young pediatric patients.

Focal hemolymphangioma of the rectum: A case report and literature review

RATIONALE

Gastrointestinal hemolymphangiomas are very rare, especially in the rectum. Only 3 cases of rectal hemolymphangioma, all of which are diffuse lesions, have been reported in the English literature on PubMed. Our case is the first focal lesion of the rectum. It is important for radiologists to correctly identify the imaging features of rectal hemolymphangiomas.

PATIENT CONCERNS

A 51-year-old woman visited our hospital because of intermittent constipation for 3 years.

DIAGNOSES

Colonoscopy revealed a prominent lesion on the left anterior wall of the lower rectum. Transvaginal color Doppler ultrasonography showed that the posterior vaginal wall area had a mixed-echo mass, and blood flow signals of the dots and stripes could be seen. Pelvic magnetic resonance imaging showed that the cystic space-occupying lesion in the region between the left anterior wall of the lower rectum and the posterior wall of the middle and lower vagina had a clear boundary.

INTERVENTIONS

The patient underwent surgery to remove the rectal lesions. The surgical specimen was finally diagnosed as local hemolymphangioma by pathological analysis.

LESSONS

Localized hemolymphangioma of the rectum is very rare, and imaging examination is essential for the diagnosis and evaluation of the extent of lesion invasion.