Individuals with sessile serrated polyps express an aggressive colorectal phenotype

Artificial intelligence applications in predicting the behavior of gastrointestinal cancers in pathology

Recent research has provided a wealth of data supporting the application of artificial intelligence (AI)-based applications in routine pathology practice. Indeed, it is clear that these methods can significantly support an accurate and rapid diagnosis by eliminating errors, increasing reliability, and improving workflow. In addition, the effectiveness of AI in the pathological evaluation of prognostic parameters associated with behavior, course, and treatment in many types of tumors has also been noted. Regarding gastrointestinal system (GIS) cancers, the contribution of AI methods to pathological diagnosis has been investigated in many studies. On the other hand, studies focusing on AI applications in evaluating parameters to determine tumor behavior are relatively few. For this purpose, the potential of AI models has been studied over a broad spectrum, from tumor subtyping to the identification of new digital biomarkers. The capacity of AI to infer genetic alterations of cancer tissues from digital slides has been demonstrated. Although current data suggest the merit of AI-based approaches in assessing tumor behavior in GIS cancers, a wide range of challenges still need to be solved, from laboratory infrastructure to improving the robustness of algorithms, before incorporating AI applications into real-life GIS pathology practice. This review aims to present data from AI applications in evaluating pathological parameters related to the behavior of GIS cancer with an overview of the opportunities and challenges encountered in implementing AI in pathology.

Sessile serrated lesions: Clinicopathological characteristics, endoscopic diagnosis, and management

The 2019 World Health Organization (WHO) Classification of Tumours of the Digestive System (5th edition) introduced the term "sessile serrated lesion" (SSL) to replace the term "sessile serrated adenoma/polyp" (SSA/P). SSLs are early precursor lesions in the serrated neoplasia pathway that result in colorectal carcinomas with BRAF mutations, methylation for DNA repair genes, a CpG island methylator phenotype, and high levels of microsatellite instability. Some of these lesions can rapidly become dysplastic or invasive carcinomas that exhibit high lymphatic invasion and lymph node metastasis potential. The 2019 WHO classification noted that dysplasia arising in an SSL most likely is an advanced polyp, regardless of the morphologic grade of the dysplasia. Detecting SSLs with or without dysplasia is critical; however, detection of SSLs is challenging, and their identification by endoscopists and pathologists is inconsistent. Furthermore, indications for their endoscopic treatment have not been established. Moreover, SSLs are considered to contribute to the development of post-colonoscopy colorectal cancers. Herein, the clinicopathological and endoscopic characteristics of SSLs, including features determined using white light and image-enhanced endoscopy, therapeutic indications, therapeutic methods, and surveillance are reviewed based on the literature. This information may lead to more intensive research to improve detection, diagnosis, and rates of complete resection of these lesions and reduce post-colonoscopy colorectal cancer rates.

Current Developments of Artificial Intelligence in Digital Pathology and Its Future Clinical Applications in Gastrointestinal Cancers

The implementation of DP will revolutionize current practice by providing pathologists with additional tools and algorithms to improve workflow. Furthermore, DP will open up opportunities for development of AI-based tools for more precise and reproducible diagnosis through computational pathology. One of the key features of AI is its capability to generate perceptions and recognize patterns beyond the human senses. Thus, the incorporation of AI into DP can reveal additional morphological features and information. At the current rate of AI development and adoption of DP, the interest in computational pathology is expected to rise in tandem. There have already been promising developments related to AI-based solutions in prostate cancer detection; however, in the GI tract, development of more sophisticated algorithms is required to facilitate histological assessment of GI specimens for early and accurate diagnosis. In this review, we aim to provide an overview of the current histological practices in AP laboratories with respect to challenges faced in image preprocessing, present the existing AI-based algorithms, discuss their limitations and present clinical insight with respect to the application of AI in early detection and diagnosis of GI cancer.

Deep Neural Network Models for Colon Cancer Screening

Early detection of colorectal cancer can significantly facilitate clinicians' decision-making and reduce their workload. This can be achieved using automatic systems with endoscopic and histological images. Recently, the success of deep learning has motivated the development of image- and video-based polyp identification and segmentation. Currently, most diagnostic colonoscopy rooms utilize artificial intelligence methods that are considered to perform well in predicting invasive cancer. Convolutional neural network-based architectures, together with image patches and preprocesses are often widely used. Furthermore, learning transfer and end-to-end learning techniques have been adopted for detection and localization tasks, which improve accuracy and reduce user dependence with limited datasets. However, explainable deep networks that provide transparency, interpretability, reliability, and fairness in clinical diagnostics are preferred. In this review, we summarize the latest advances in such models, with or without transparency, for the prediction of colorectal cancer and also address the knowledge gap in the upcoming technology.

Self-reported Metabolic Risk Factor Associations with Adenomatous, Sessile Serrated, and Synchronous Adenomatous and Sessile Serrated Polyps

Studies have found a positive association between metabolic risk factors, such as obesity and diabetes, and adenomatous polyps (AP). However, fewer studies have assessed the association between sessile serrated polyps (SSP) or synchronous diagnosis of APs and SSPs (synch polyps). Study participants (N = 1,370; ages 40-85) undergoing screening colonoscopy were enrolled between August 2016 and February 2020. Self-reported metabolic risk factors, including diabetes, hypertension, hyperlipidemia, and overweight/obesity, were evaluated for associations with new diagnoses of APs, SSPs, and synch polyps at the present colonoscopy. Average participant age was 60.73 ± 8.63 (SD) years; 56.7% were female and 90.9% white. In an assessment of individual metabolic risk factors, adjusted for age, sex, race, and smoking status, increased body mass index (BMI; overweight or obese vs. normal BMI of <25 kg/m2) was associated with an increased odds for new onset of colon APs (P trend < 0.001) as was a diagnosis of diabetes [adjusted conditional OR (aCOR) = 1.59 (1.10-2.29)]. No associations were seen between the metabolic risk factors and onset of SSPs. Being obese or hypertensive each increased the odds of new onset of synch polyps with aCOR values of 2.09 (1.01-4.32) and 1.79 (1.06-3.02), respectively. Self-reported risk factors may help assess polyp type risk. Because SSPs and synch polyps are rare, larger studies are needed to improve our understanding of the contribution of these factors to polyp risk. These data lead us to hypothesize that differences in observed metabolic risk factors between polyp types reflect select metabolic impact on pathways to colorectal cancer. PREVENTION RELEVANCE: Self-reported medical history provides valuable insight into polyp risk, potentially enabling the use of larger retrospective studies of colonoscopy populations to assess knowledge gaps. More aggressive colonoscopy screening, critical to colorectal cancer prevention, may be considered in populations of individuals with metabolic risk factors and modifiable lifestyle risk factors.

Features associated with high-risk sessile serrated polyps at index and follow-up colonoscopy

BACKGROUND AND AIM

Clinically significant serrated polyps are precursors of colorectal cancers, with features considered high risk including size ≥10 mm, dysplasia, and presence of synchronous conventional adenoma. While these features have been described in cohorts undergoing screening colonoscopy, there is little information regarding the prevalence and patient characteristics associated with high-risk sessile serrated polyps (SSPs) in those undergoing surveillance colonoscopy.

METHODS

Polyp pathology at the index and first follow-up colonoscopy performed between 2004 and 2019 were examined in patients enrolled in a surveillance program because of an index finding of adenoma and/or SSP. Demographics and pathology features for SSP were compared between the colonoscopies.

RESULTS

Of 6297 patients undergoing index colonoscopy, 2035 underwent follow-up colonoscopy after 3.3 years (interquartile range 2.1-4.8 years). The proportion with SSP decreased from 7.6% at index to 5.0% at follow-up (P < 0.001); however, the proportion of SSPs that were considered high risk was not different between the colonoscopies (62.8% vs 62.4%). Female gender was associated with the presence of high-risk SSP at index colonoscopy (odds ratio [OR] 1.62, 95% confidence interval [CI] 1.28-2.06), while age ≥75 years (OR 3.38, 95% CI 1.67-6.81) and previous high-risk SSP (OR 9.40, 95% CI 4.23-20.88) were independently associated with high-risk SSP at follow-up.

CONCLUSIONS

The prevalence of SSP falls by one-third at first follow-up colonoscopy although the proportion of SSP with high-risk features remains the same. While females were more likely to have a high-risk SSP at the index colonoscopy, those at greatest risk for high-risk SSP at follow-up colonoscopy were age >75 years and an index high-risk SSP.

Histopathology classification and localization of colorectal cancer using global labels by weakly supervised deep learning

Colorectal cancer (CRC) is the second leading cause of cancer-related mortality worldwide. In coping with it, histopathology image analysis (HIA) provides key information for clinical diagnosis of CRC. Nowadays, the deep learning methods are widely used in improving cancer classification and localization of tumor-regions in HIA. However, these efforts are both time-consuming and labor-intensive due to the manual annotation of tumor-regions in the whole slide images (WSIs). Furthermore, classical deep learning methods to analyze thousands of patches extracted from WSIs may cause loss of integrated information of image. Herein, a novel method was developed, which used only global labels to achieve WSI classification and localization of carcinoma by combining features from different magnifications of WSIs. The model was trained and tested using 1346 colorectal cancer WSIs from the Cancer Genome Atlas (TCGA). Our method classified colorectal cancer with an accuracy of 94.6 %, which slightly outperforms most of the existing methods. Its cancerous-location probability maps were in good agreement with annotations from three individual expert pathologists. Independent tests on 50 newly-collected colorectal cancer WSIs from hospitals produced 92.0 % accuracy and cancerous-location probability maps were in good agreement with the three pathologists. The results thereby demonstrated that the method sufficiently achieved WSI classification and localization utilizing only global labels. This weakly supervised deep learning method is effective in time and cost, as it delivered a better performance in comparison with the state-of-the-art methods.

Relationship between serrated polyps and synchronous and metachronous advanced neoplasia: A retrospective study

OBJECTIVE

Serrated polyps (SP) are regarded as precursor lesions of colorectal cancer (CRC). We conducted this single-center study aiming to investigate the relationship between SP and synchronous and metachronous advanced neoplasia in the Chinese population.

METHODS

The data for this retrospective study were collected from the Endoscopy Center and Department of Gastroenterology of Renji Hospital, School of Medicine, Shanghai Jiao Tong University between May 2012 and May 2019. Altogether 2205 patients were pathologically confirmed with colorectal SP.

RESULTS

The detection rate of SP among all polyps has gradually increased since 2014 and reached 8.74% by 2019. Among all the SP cases, 1540 (69.84%) were confirmed as having hyperplasic polyps (HP), 486 (22.04%) were having sessile serrated lesions (SSL), and 171 (7.76%) had traditional serrated adenomas (TSA). Compared with HP (2.14%), SSL and TSA were larger and more likely to be accompanied by synchronous and metachronous advanced neoplasia (6.79% and 6.08%). We next found that large SP (diameter ≥10 mm) (odds ratio [OR] 2.52, 95% confidence interval [CI] 1.40-4.55, P = 0.002) and SSL with high-grade intraepithelial neoplasia (OR 13.85, 95% CI 3.28-58.56, P < 0.001) were associated with an increased risk of synchronous advanced neoplasia. However, we failed to find a relationship between SP and metachronous advanced neoplasia because few patients had developed metachronous advanced neoplasia.

CONCLUSION

Large SP and SSL with high-grade intraepithelial neoplasia are associated with synchronous advanced neoplasia and require timely surveillance.

Patterns of polyp histology: predictors of peril in the mucosa

BACKGROUND

Precursor colonic polyps of varied subtypes correlate with the known neoplastic pathways. When patients present with synchronous pre-malignant polyps of multiple histologies, multiple genetic mechanisms are likely to be active, potentially resulting in a more unstable, tumourigenic mucosa.

METHODS

We hypothesized that patients with a combination of sessile serrated adenomas/polyps (SSA/Ps), hyperplastic (HP) polyps and adenomas would be at highest risk of developing dysplasia/cancer compared to SSA/Ps alone, due to the synergistic effect of multiple active carcinogenic pathways. A prospective colonoscopy database was examined for patients with a history of SSA/P. Patients were placed into four groups based on patterns of polyp histology as follows: (i) only SSA/Ps; (ii) SSA/P + HP; (iii) SSA/Ps + adenomas; and (iv) SSA/Ps + HP + adenomas. These groups were compared in terms of the numbers, size, location and histology of polyps and personal or family history of colorectal cancer.

RESULTS

A total of 374 patients were included. The average age was 70 years (range 21-88), and 43% were male. There was a trend towards the most aggressive neoplastic pattern in group 4, associated with a tendency to larger SSA/Ps, more villous architecture in the adenomas and more high-grade dysplasia in both types of polyps. It was also associated with multiplicity of both SSA/Ps and adenomas. No SSA/Ps existing in the absence of adenomas had cytological dysplasia.

CONCLUSION

The combination of SSA/Ps, HP and adenomas in the colorectal epithelium seems to be a marker for aggressive carcinogenesis and suggests that accurate and effective surveillance is important to manage this risk.

Colorectal sessile serrated lesion with large size or synchronous neoplasm: a prospective study

BACKGROUND

Colorectal sessile serrated lesion (SSL) with synchronous neoplasm or large size are linked to higher risk of cancer, but their characteristics are unclear.

METHODS

We prospectively included consecutive colorectal hyperplasic polyp and SSL collected at our institution from August 2011 to August 2012. The following data were collected and analyzed: age, gender, polyp site, aggregated polyp size, history of polyp, and synchronous neoplasm.

RESULTS

We collected 437 specimens including 353 (80.8%) hyperplasic polyp and 84 (19.2%) SSL. Compared with hyperplasic polyp, SSL was independently associated with proximal colon [odds ratio (OR) 3.61, P< 0.001], larger size (OR 3.98, P< 0.001), but not history of polyp, age or gender. Large SSL (≥1 vs <1 cm) was associated with polyp site (P= 0.035) and synchronous advanced adenoma and cancer (P< 0.001). SSL with synchronous adenoma and cancer were more likely found in males (OR 1.91, P= 0.001), elderly (OR 1.02, P= 0.033), and patients with the index polyp in proximal colon (OR 1.32, P= 0.022), but not related to history of adenoma and cancer. Moreover, synchronous adenoma, SSL and cancer were independently associated with male gender (OR 1.90, P< 0.001), but surprisingly not older age, histology of index polyp (SSL vs hyperplasic polyp), index-polyp site or history of adenoma and cancer.

CONCLUSIONS

This prospective study shows male gender is associated with both synchronous adenoma and cancer, and synchronous adenoma, SSL and cancer, while index polyp site is associated with synchronous adenoma and cancer.

The heterogeneous clinical and pathological landscapes of metastatic Braf-mutated colorectal cancer

Colorectal cancer (CRC) is a complex and molecularly heterogeneous disease representing one of the most frequent causes of cancer-related death worldwide. About 8-15% of CRCs harbor a mutation in BRAF gene, a proto-oncogene involved in cell proliferation, differentiation and survival through the MAPK signaling cascade. The acquisition of BRAF mutation is an early event in the "serrated" CRC carcinogenetic pathway and is associated with specific and aggressive clinico-pathological and molecular features. Despite that the presence of BRAF mutation is a well-recognized negative prognostic biomarker in metastatic CRC (mCRC), a great heterogeneity in survival outcome characterizes these patients, due to the complex, and still not completely fully elucidated, interactions between the clinical, genetic and epigenetic landscape of BRAF mutations. Because of the great aggressiveness of BRAF-mutated mCRCs, only 60% of patients can receive a second-line chemotherapy; so intensive combined and tailored first-line approach could be a potentially effective strategy, but to minimize the selective pressure of resistant clones and to reduce side effects, a better stratification of patients bearing BRAF mutations is needed.

Risk factors of traditional serrated adenoma and clinicopathologic characteristics of synchronous conventional adenoma

BACKGROUND AND AIMS

Traditional serrated adenoma (TSA) is rare and known to have a malignant potential. We aimed to investigate the prevalence and risk factors of TSA and compare the characteristics of synchronous conventional adenoma (AD) in patients with TSA with those of AD in patients with AD only.

METHODS

We reviewed medical records of 31,932 healthy subjects who underwent screening colonoscopy at a single hospital between 2012 and 2017.

RESULTS

TSA was observed in 116 patients (.4%). Among them, 47 patients (40.5%) had TSA only and 69 patients (59.5%) had synchronous AD. Multivariable analysis showed independent risk factors for TSA to include age ≥50 years (odds ratio [OR], 3.34; 95% confidence interval [CI], 1.72-6.49; P < .001), hypertension (OR, 2.07; 95% CI, 1.09-3.92; P = .026), and current smoking (OR, 2.58; 95% CI, 1.28-5.23; P = .008). There were significantly more ADs (2.5 ± 2.0 vs 1.8 ± 1.6, P = .009) and ADs were of larger size (6.7 ± 5.0 vs 5.3 ± 3.6 mm, P = .027) in TSA patients than in AD-only patients. Furthermore, advanced adenoma and high-risk adenoma were more frequently observed in TSA patients than in AD-only patients (24.2% vs 11.2%, P = .002; 43.5% vs 23.6%, P < .001).

CONCLUSIONS

The prevalence of TSA in healthy adults was .4%. Age ≥50 years, hypertension, and current smoking may be risk factors of TSA. Synchronous AD is often observed with TSA and may show more advanced features than those in AD-only patients.

Terminology, Molecular Features, Epidemiology, and Management of Serrated Colorectal Neoplasia

In addition to the adenoma to carcinoma sequence, colorectal carcinogenesis can occur via the serrated pathway. Studies have focused on clarification of categories and molecular features of serrated polyps, as well as endoscopic detection and risk assessment. Guidelines from the World Health Organization propose assigning serrated polyps to categories of hyperplastic polyps, traditional serrated adenomas, and sessile serrated lesions (SSLs). Traditional serrated adenomas and SSLs are precursors to colorectal cancer. The serrated pathway is characterized by mutations in RAS and RAF, disruptions to the Wnt signaling pathway, and widespread methylation of CpG islands. Epidemiology studies of serrated polyps have been hampered by inconsistencies in terminology and reporting, but the prevalence of serrated class polyps is 20%-40% in average-risk individuals; most serrated polyps detected are hyperplastic. SSLs, the most common premalignant serrated subtype, and are found in up to 15% of average-risk patients by high-detecting endoscopists. Variations in rate of endoscopic detection of serrated polyps indicate the need for careful examination, with adequate bowel preparation and sufficient withdrawal times. Risk factors for SSLs include white race, family history of colorectal cancer, smoking, and alcohol intake. Patients with serrated polyps, particularly SSLs and traditional serrated adenomas, have an increased risk of synchronous and metachronous advanced neoplasia. Surveillance guidelines vary among countries, but SSLs and proximal hyperplastic polyps require special attention in assignment of surveillance interval-especially in light of concerns regarding incomplete detection and resection.

Sessile Serrated Polyps with Synchronous Conventional Adenomas Increase Risk of Future Advanced Neoplasia

BACKGROUND

Surveillance colonoscopy guidelines following adenomas or sessile serrated adenomas/polyps (SSPs) are based on pathology features known to be associated with risk of future colorectal cancer. A synchronous conventional adenoma may increase the malignant potential of SSP, but current guidelines do not address this combination of pathologies.

AIMS

The aim was to assess the risk of advanced neoplasia after SSP with or without synchronous adenoma compared to that following a conventional adenoma.

METHODS

An audit was conducted on colonoscopies performed between 2000 and 2014 as part of a surveillance program. Index colonoscopy findings were classified as: low-risk SSP and high-risk SSP (size ≥ 10 mm or with cytological dysplasia) with and without synchronous adenoma; high-risk adenoma and low-risk adenoma. Risk of advanced neoplasia was determined at subsequent surveillance colonoscopies.

RESULTS

In total, 2157 patients had adenoma or SSP found at index colonoscopy-low-risk adenoma (40%), high-risk adenoma (54%) and SSP (4%). Synchronous adenomas were seen with 47% of SSP. The median follow-up was 50.3 months (interquartile range 28.1-79.3). Compared to an index finding of low-risk adenoma, index findings of high-risk adenoma, as well as SSP with synchronous adenoma, were independent predictors of future advanced neoplasia (high-risk adenoma: hazard ratio (HR) = 2.04 (95% CI 1.70-2.45); high-risk SSP + adenoma HR = 3.20 (95% CI 1.31-7.82); low-risk SSP + adenoma: HR = 2.20 (95% CI 1.03-4.68)).

CONCLUSIONS

Synchronous adenoma increases the risk of advanced neoplasia for SSP equivalent to that seen following high-risk adenoma. Guidelines for surveillance should take into account concurrent pathologies with SSP.

A rare trigger for acute appendicitis leading to small bowel obstruction: traditional serrated adenoma of the appendiceal foramen

This is the first documented case of traditional serrated adenoma (TSA) of the appendiceal foramen that triggered acute appendicitis resulting in small bowel obstruction (SBO). An 88-year-old Japanese man presented with abdominal pain, distension, and appetite loss. Computed tomography demonstrated distended ileum adherent to cecum with thickened walls. He was diagnosed with SBO, and open ileoceal resection was eventually performed. Pathological examination revealed that a pedunculated polyp had obstructed the appendiceal foramen and triggered acute appendicitis, thus leading to SBO. Histopathological examination of the polyp revealed that the long fronds of the adenoma were lined by dysplastic epithelial cells, which is a characteristic feature of TSA. This case report illustrates that a tiny TSA can trigger the obstruction of the appendiceal foramen and lead to acute appendicitis and SBO. We underline the need for the resection of the polyps in this region regardless of their size.

Sessile Serrated Adenomas in Young Patients may have Limited Risk of Malignant Progression

GOALS

To provide preliminary evidence that sessile serrated adenomas (SSA) are low-risk polyps in young patients.

BACKGROUND

SSAs are the dominant polyp of the serrated neoplasia pathway and as such are the precursor of up to 20% of colorectal carcinomas (CRC). Up to 90% of these cancers are expected to harbor a BRAF mutation. SSAs are being diagnosed with increasing frequency in young patients, placing a significant burden on colonoscopic services. Evidence to direct the surveillance intervals for these young patients is not available.

STUDY

We utilized 2 patient cohorts comprising (1) a consecutive series of patients who underwent outpatient colonoscopy through a tertiary hospital and (2) a consecutive series of resection specimens for CRC processed through a gastrointestinal pathology service. The prevalence of SSAs by age was determined in the patients undergoing colonoscopy and compared with the ages of patients with BRAF mutated CRC in the pathology series.

RESULTS

The prevalence of SSAs was similar irrespective of age. By comparison, BRAF mutated CRCs were very rare (3.8% of cases) in patients younger than 50 years of age and uncommon (9.3% of cases) in patients younger than 60 years of age, but increased to 39.8% in patients older than 80 years of age.

CONCLUSIONS

These results suggest that SSAs develop at a young age, but have a prolonged dwell time and are unlikely to develop into cancer in patients younger than 60 years of age. These findings highlight the need for further targeted research to determine the most appropriate surveillance intervals for young patients with sporadic SSAs.

Volumetric growth rates of sessile serrated adenomas/polyps observed in situ at longitudinal CT colonography

OBJECTIVE

Sessile serrated adenomas/polyps (SSA/Ps) are now recognized as potential cancer precursors, but little is known about their natural history. We assessed the in vivo growth rates of histologically proven SSA/Ps at longitudinal CT colonography (CTC) and compared results with non-advanced tubular adenomas (TAs).

METHODS

We identified a cohort of 53 patients (mean age, 54.8 ± 5.5 years; M:F, 26:27) from one center with a total of 58 SSA/Ps followed longitudinally at CTC (mean follow-up interval, 5.3 ± 1.9 years). Initial and final size measurements were determined using dedicated CTC software. Findings were compared with 141 non-advanced TAs followed at CTC (mean, 4.1 ± 2.3 years) in 113 patients (mean age, 56.8 ± 6.9 years).

RESULTS

SSA/Ps were more often flat (62% [36/58] vs. 14% [20/141], p < 0.0001) and right-sided (98% [57/58] vs. 46% [65/141], p < 0.0001) compared with TAs. Initial average diameter was greater for SSA/Ps (9.3 mm vs. 6.3 mm; p < 0.0001). Mean annual volumetric growth was + 12.7%/year for SSA/Ps vs. + 36.4%/year for TAs (p = 0.028). Using a previously defined threshold of + 20% increase in volume/year to define progression, 22% (13/58) of SSA/Ps and 41% (58/141) of TAs progressed (p = 0.014). None of the SSA/Ps had dysplasia or invasive cancer at histopathology.

CONCLUSIONS

Sessile serrated adenoma/polyps demonstrate slower growth compared with conventional non-advanced tubular adenomas, despite larger initial linear size. This less aggressive behavior may help explain the more advanced patient age for serrated pathway cancers. Furthermore, these findings could help inform future colonoscopic surveillance strategies, as current guidelines are largely restricted to expert opinion related to the absence of natural history data.

KEY POINTS

• Sessile serrated adenoma/polyps (SSA/Ps) tend to be flat, right-sided, and demonstrate slower growth compared with conventional non-advanced tubular adenomas. • This less aggressive behavior of SSA/Ps may help explain the more advanced patient age for serrated pathway cancers.

Sessile Serrated Adenomas: How to Detect, Characterize and Resect

Serrated polyps are important contributors to the burden of colorectal cancers (CRC). These lesions were once considered to have no malignant potential, but currently up to 30% of all CRC are recognized to arise from the serrated neoplasia pathway. The primary premalignant lesions are sessile serrated adenomas/polyps (SSA/Ps), although traditional serrated adenomas are relatively uncommon. Compared to conventional adenomas, SSA/Ps are morphologically subtle with indistinct borders, may be difficult to detect endoscopically, are more prevalent than previously thought, are associated with synchronous and metachronous advanced neoplasia, and have a higher risk of incomplete resection. Although many lesions remain “dormant,” progressive disease is associated with the development of dysplasia and more rapid progression to CRC. As a result, SSA/Ps are strongly implicated in the development of interval cancers. These factors represent unique challenges that require a meticulous approach to their management. In this review, we summarize the contemporary literature on the characterization, detection and resection of SSA/Ps.

Adenomas - Genetic factors in colorectal cancer prevention

Colorectal cancer is the second most common type of cancer both in Europe and Poland. During the last 30 years more than a 3-fold increase has been observed in Poland due to environmental and genetic factors. Almost all colorectal malignancies are related to the formation and malignant transformation of colorectal dysplasia and adenoma. Efforts aiming to decrease the number of colorectal cancer deaths are focused on the disease early detection. Genetic diagnosis for hereditary syndromes predisposing to colorectal cancer has been developed and is a part of the routine treatment. Most cancers are sporadic. They often develop from polyps in the colon. In addition to the genetic events described in the 1990s, showing the adenoma transformation into carcinoma that has been a prime example of malignant transformation for a long time, there are also other possibilities of neoplastic transformation. The recognition of colorectal cancer risk factors make sense as their nature is lifestyle- and diet-related. In this review paper those risk factors are presented and the prevention of colorectal cancer is discussed taking into account genetic factors.

Clinical outcomes of surveillance colonoscopy for patients with sessile serrated adenoma

Background/Aims

Sessile serrated adenomas (SSAs) are known to be precursors of colorectal cancer (CRC). The proper interval of follow-up colonoscopy for SSAs is still being debated. We sought to determine the proper interval of colonoscopy surveillance in patients diagnosed with SSAs in South Korea.

Methods

We retrospectively reviewed the medical records of patients diagnosed with SSAs who received 1 or more follow-up colonoscopies. The information reviewed included patient baseline characteristics, SSA characteristics, and colonoscopy information.

Results

From January 2007 to December 2011, 152 SSAs and 8 synchronous adenocarcinomas were identified in 138 patients. The mean age of the patients was 62.2 years and 60.1% patients were men. SSAs were located in the right colon (i.e., from the cecum to the hepatic flexure) in 68.4% patients. At the first follow-up, 27 SSAs were identified in 138 patients (right colon, 66.7%). At the second follow-up, 6 SSAs were identified in 65 patients (right colon, 66.7%). At the 3rd and 4th follow-up, 21 and 11 patients underwent colonoscopy, respectively, and no SSAs were detected. The total mean follow-up duration was 33.9 months. The mean size of SSAs was 8.1±5.0 mm. SSAs were most commonly found in the right colon (126/185, 68.1%). During annual follow-up colonoscopy surveillance, no cancer was detected.

Conclusions

Annual colonoscopy surveillance is not necessary for identifying new CRCs in all patients diagnosed with SSAs. In addition, the right colon should be examined more carefully because SSAs occur more frequently in the right colon during initial and follow-up colonoscopies.

What influences preneoplastic colorectal lesion recurrence?

The hypothesis of the local recurrence of preneoplastic lesions was first put forward in the 1950s. Disease recurrence may result from an inherent imbalance in cell proliferation that promotes carcinogenesis in apparently normal mucosa. Our review sheds light on how early preneoplastic lesions could be used to diagnose relapsed preneoplastic and, developing neoplastic lesions. We focus in detail on the clinical-pathological and molecular features of adenoma subtypes and their role in relapsed adenoma and their development into colorectal carcinoma. Moreover, we include the data available on microbiota and its metabolites and their role in recurrence. We strongly believe that a significant improvement could be achieved in colorectal screening by introducing personalized endoscopic surveillance for polyp-bearing patients on the basis of the presence of molecular markers that are predictive of recurrence.

Deep Learning for Classification of Colorectal Polyps on Whole-slide Images

CONTEXT

Histopathological characterization of colorectal polyps is critical for determining the risk of colorectal cancer and future rates of surveillance for patients. However, this characterization is a challenging task and suffers from significant inter- and intra-observer variability.

AIMS

We built an automatic image analysis method that can accurately classify different types of colorectal polyps on whole-slide images to help pathologists with this characterization and diagnosis.

SETTING AND DESIGN

Our method is based on deep-learning techniques, which rely on numerous levels of abstraction for data representation and have shown state-of-the-art results for various image analysis tasks.

SUBJECTS AND METHODS

Our method covers five common types of polyps (i.e., hyperplastic, sessile serrated, traditional serrated, tubular, and tubulovillous/villous) that are included in the US Multisociety Task Force guidelines for colorectal cancer risk assessment and surveillance. We developed multiple deep-learning approaches by leveraging a dataset of 2074 crop images, which were annotated by multiple domain expert pathologists as reference standards.

STATISTICAL ANALYSIS

We evaluated our method on an independent test set of 239 whole-slide images and measured standard machine-learning evaluation metrics of accuracy, precision, recall, and F1 score and their 95% confidence intervals.

RESULTS

Our evaluation shows that our method with residual network architecture achieves the best performance for classification of colorectal polyps on whole-slide images (overall accuracy: 93.0%, 95% confidence interval: 89.0%-95.9%).

CONCLUSIONS

Our method can reduce the cognitive burden on pathologists and improve their efficacy in histopathological characterization of colorectal polyps and in subsequent risk assessment and follow-up recommendations.

Sessile Serrated Polyps and Colon Cancer Prevention

Evidence suggests that up to one fifth of colorectal carcinomas develop from serrated polyps, named for their pattern of colonic crypts, and include the sessile serrated adenoma/polyp (SSA/P) that has malignant potential. SSA/Ps are typically located in the proximal colon and have molecular features of hypermethylation of CpG islands in gene promoters and activating point mutations (V600E) in the BRAF oncogene. Both of these features are seen in sporadic colorectal carcinomas with microsatellite instability (MSI) which is potentially consistent with an origin of these cancers from precursor SSA/Ps. Dysplasia is detected in a subset of SSA/Ps with a high risk of progression to carcinoma. An uncommon serrated polyp is the traditional serrated adenoma that is typically found in the left colon, has a tubulovillous architecture, and frequently harbors mutant KRAS To date, the epidemiology of these serrated lesions is poorly understood, and limited observational data suggest a potential chemopreventive benefit of nonsteroidal anti-inflammatory drugs. The current primary strategy to reduce the risk of colorectal carcinoma from serrated polyps is to enhance their detection at colonoscopy and to ensure their complete removal. This review provides insight into the epidemiologic, clinical, histopathologic, and molecular features of serrated polyps and includes data on their endoscopic detection and chemoprevention. Cancer Prev Res; 10(5); 270-8. ©2017 AACR.

Increased Risk of Colorectal Cancer Development Among Patients With Serrated Polyps

BACKGROUND & AIMS

Sessile serrated adenomas/polyps (SSA/Ps) and traditional serrated adenomas (TSAs) are now distinguished from hyperplastic polyps and recognized as precursors to colorectal cancer (CRC). We studied CRC risks associated with serrated polyps.

METHODS

By using Danish databases (1977-2009), we conducted a nationwide population-based, case-control study nested within individuals who had received colonoscopies (n = 272,342), and identified 2045 CRC cases and 8105 CRC-free individuals (controls). For each case and control, we identified the first colorectal polyp(s) that underwent a biopsy or were excised during or after the initial colonoscopy, and obtained tissue blocks for hyperplastic lesions. Four expert pathologists reviewed these lesions using current terminology for serrated polyps. We used logistic regression to compute odds ratios (ORs) to associate the risk of CRC with polyp type and estimated the absolute risks by multiplying the risk in patients with no polyps by these ORs.

RESULTS

Seventy-nine cases and 142 controls had SSA/Ps (OR, 3.07; 95% confidence interval [CI], 2.30-4.10). SSA/Ps with cytology markers of dysplasia were associated with a particularly high OR (4.76; 95% CI, 2.59-8.73). Women with SSA/P had a higher risk for CRC than men with SSA/P (OR for women, 5.05; 95% CI, 3.05-8.37 vs OR for men, 2.18; 95% CI, 1.24-3.82); patients with SSA/P proximal to the splenic flexure had the highest risk for CRC (OR, 12.42; 95% CI, 4.88-31.58). The OR for CRC was 4.84 in the 14 cases vs 17 controls with TSAs (95% CI, 2.36-9.93), 2.51 in the 757 cases vs 1698 controls with conventional adenomas (95% CI, 2.25-2.80), and 1.30 in the 55 cases vs 235 controls with hyperplastic polyps (95% CI, 0.96-1.77). The 10-year risk for CRC was 4.4% for patients with SSA/P with dysplasia, 4.5% for patients with TSAs, and 2.3% for patients with conventional adenomas.

CONCLUSION

Patients with SSA/P or TSA are at increased risk for CRC; their level of risk is similar to or higher than that of patients with conventional adenomas.

[Serrated polyps and their association with synchronous advanced colorectal neoplasia]

INTRODUCTION

Large serrated polyps (SP), proximal SP, SP with dysplasia and the presence of multiple sessile serrated adenomas/polyps (SSA/P), which we refer to as SP with increased risk of metachronous lesions (SPIRML), have been associated with an increased risk of advanced colon lesions on follow-up. It is unclear, however, whether SPIRML are also associated with an increased risk of synchronous advanced colorectal neoplasia (ACN).

AIM

The aim of this study was to estimate the prevalence of SPIRML and to evaluate the association between SPIRML and synchronous ACN.

METHODS

A cross-sectional population-based study in all patients (1,538) with histological diagnosis of SP obtained from colonoscopies, sigmoidoscopies and colonic surgery performed in Navarra Health Service hospitals (Spain) in 2011. Demographic parameters and synchronous colonic lesions (adenomas, advanced adenomas [AA] and ACN) were analyzed.

RESULTS

One fourth of the sample (384 patients) presented SPIRML. These were older patients, with a slight predominance of women, and with no differences in body mass index (BMI) compared to patients without SPIRML. In the univariate analysis, patients with SPIRML showed an increased risk of adenoma, AA and ACN. In the multivariate analysis, the SPIRML group had a higher risk of synchronous AA and ACN (odds ratio [OR]: 2.38 [1.77-3.21] and OR: 2.29 [1.72-3.05], respectively); in the case of ACN, this risk was statistically significant in both locations (proximal or distal), with OR slightly higher for the proximal location. Different subtypes of SPIRML had a higher risk of AA and synchronous NA.

CONCLUSION

SPIRML were common in patients with SP, and their presence was associated with an increased risk of synchronous ACN.

Long-term risk of colorectal cancer in individuals with serrated polyps

OBJECTIVE

Although serrated polyps may be precursors of colorectal cancer (CRC), prospective data on the long-term CRC risk in individuals with serrated polyps are lacking.

DESIGN

In a population-based randomised trial, 12,955 individuals aged 50-64 years were screened with flexible sigmoidoscopy, while 78 220 individuals comprised the control arm. We used Cox models to estimate HRs with 95% CIs for CRC among individuals with ≥1 large serrated polyp (≥10 mm in diameter), compared with individuals with adenomas at screening, and to population controls, and multivariate logistic regression to assess polyp risk factors for CRC.

RESULTS

A total of 103 individuals had large serrated polyps, of which 81 were included in the analyses. Non-advanced adenomas were found in 1488 individuals, advanced adenomas in 701. Median follow-up was 10.9 years. Compared with the control arm, the HR for CRC was 2.5 (95% CI 0.8 to 7.8) in individuals with large serrated polyps, 2.0 (95% CI 1.3 to 2.9) in individuals with advanced adenomas and 0.6 (95% CI 0.4 to 1.1) in individuals with non-advanced adenomas. A large serrated polyp was an independent risk factor for CRC, adjusted for histology, size and multiplicity of concomitant adenomas (OR 3.3; 95% CI 1.3 to 8.6). Twenty-three large serrated polyps found at screening were left in situ for a median of 11.0 years. None developed into a malignant tumour.

CONCLUSIONS

Individuals with large serrated polyps have an increased risk of CRC, comparable with individuals with advanced adenomas. However, this risk may not be related to malignant growth of the serrated polyp.

TRIAL REGISTRATION NUMBER

The Norwegian Colorectal Cancer Screening trial is registered at clinicaltrials.gov (NCT00119912).

Serrated polyps and the risk of synchronous colorectal advanced neoplasia: a systematic review and meta-analysis

OBJECTIVES

Serrated polyps of the colon comprise a heterogeneous group of lesions with distinct histological and malignant features. The presence of serrated polyps has been associated with synchronous advanced neoplasia, although the magnitude of this relationship is unclear.

METHODS

Using studies identified from systematic literature search up to February 2014, we performed a systematic review and meta-analysis to estimate the pooled prevalence of serrated polyps and their association with synchronous advanced neoplasia. Random-effects models were used to combine estimates from heterogeneous studies, and odds ratios (ORs) with 95% confidence intervals (CIs) were presented.

RESULTS

Nine studies with 34,084 participants were included. The mean age of subjects was 59.9±6.6 years and 52.5% of the subjects were male. Pooled prevalence of serrated polyps was 15.6% (95% CI, 10.3-22.9%). The pooled OR of advanced neoplasia in individuals with serrated polyps was 2.05 (95% CI, 1.38-3.04). Pooled analysis showed that the presence of proximal serrated polyps (OR=2.77, 95% CI, 1.71-4.46) and large serrated polyps (OR=4.10, 95% CI, 2.69-6.26) was associated with an increased risk of synchronous advanced neoplasia. The pooled OR for advanced neoplasia in individuals with proximal and large serrated polyps was 3.35 (95% CI, 2.51-4.46). Considerable heterogeneity was observed in most analyses.

CONCLUSIONS

Our meta-analysis showed that serrated polyps are associated with a more than twofold increased risk of detection of synchronous advanced neoplasia. Individuals with proximal and large serrated polyps have the highest risk. These individuals deserve surveillance colonoscopy.

Colorectal cancer screening and prevention in women

Colorectal cancer (CRC) is one of the leading cancers and cause of cancer deaths in American women and men. Females and males share a similar lifetime cumulative risk of CRC however, substantial differences in risk factors, tumor biology, and effectiveness of cancer prevention services have been observed between them. This review distills the evidence documenting the unique variation observed between the genders relating to CRC risk factors, screening and prevention. Consistent evidence throughout the world demonstrates that women reach equivalent levels of adenomas and CRC as men but it occurs nearly a decade later in life than in their male counterparts. Women have a higher proportion of tumors which are hypermethylated, have microsatellite instability and located in the proximal colon suggesting the serrated pathway may be of greater consequence in them than in men. Other CRC risk factors such as smoking, diet and obesity have been shown to have disparate effects on women which may related to interactions between estrogen exposure, body fat distribution, and the biologic underpinnings of their tumors. There is data showing the uptake, choice, and efficacy of different CRC screening methods in women is dissimilar to that in men. The mortality benefit from FOBT, sigmoidoscopy, and protection from interval CRC by colonoscopy appears to be lower in women than men. A greater understanding of these gender idiosyncrasies will facilitate an personalized approach to CRC prevention and should ultimately lead to a reduced burden of disease.

How does the serrated polyp pathway alter CRC screening and surveillance?

Screening and surveillance for colorectal cancer (CRC) reduces mortality through the detection of early-stage adenocarcinoma, and more importantly the detection and removal of premalignant polyps. While adenomas have historically been considered the most common and screening-relevant precursor lesions, there is accumulating evidence showing that the serrated pathway is an important contributor to CRC, and a disproportionate contributor to interval or postcolonoscopy CRC, particularly in the proximal colon. The serrated pathway is characterized by mutations in the BRAF gene, high levels of methylation of promoter CpG islands (CIMP-high), and the sessile serrated adenoma/polyp (SSA/P) is the most important precursor lesion. The study of serrated polyps has been complicated by evolving nomenclature, substantial variation among pathologists in the identification of SSA/Ps, high variability in endoscopic detection rates, and uncertainty regarding the relation to synchronous and metachronous colonic neoplasia. This paper presents an overview of the serrated polyp pathway and discusses its clinical implications including its impact on CRC screening.

Sessile serrated polyps: detection, eradication, and prevention of the evil twin

OPINION STATEMENT

The sessile serrated polyp (SSP), also known as sessile serrated adenoma, is the evil twin among the colorectal cancer precursors. As will be described, these lesions have multiple aliases (serrated adenoma, serrated polyp, or serrated lesion among others), they hang out in a bad neighborhood (the poorly prepped right colon), they hide behind a mask of mucus, they are difficult for witnesses (pathologists) to identify, they are difficult for police (endoscopists) to find, they are difficult to permanently remove from the society (high incomplete resection rate), they can be impulsive (progress rapidly to colorectal cancer (CRC)), and enforcers (gastroenterologists) do not know how best to control them (uncertain surveillance recommendations). There is no wonder that there is a need to understand these lesions well, learn how best to prevent the colonic mucosa from going down this errant path or, if that fails, detect these deviants and eradicate them from the colonic society. These lesions should be on endoscopists' most wanted list.

Sessile serrated adenomas: an evidence-based guide to management

The concept of serrated colorectal neoplasia and a serrated pathway to colorectal cancer (CRC) is relatively new and continuing to evolve, but it has become highly relevant to gastroenterologists, pathologist, and oncologists alike. Sessile serrated adenomas (SSA) are now thought to be the major precursor lesion of serrated pathway cancers, which represent up to one-third of all sporadic CRC cases. However, despite their increasingly recognized importance, relatively little is known about the epidemiology and natural history of SSAs, and the molecular and epigenetic aspects are incompletely understood. Endoscopists must be aware of the unique features of SSAs so that the practice of colonoscopic screening for CRC can include optimized detection, removal, and appropriate surveillance of SSAs and other serrated precursor lesions. In this review, we discuss the history, epidemiology, and pathologic aspects of SSAs, as well as a recommended management approach and a discussion of uncertainties and opportunities for future research.

Serrated neoplasia of the colon: what do we really know?

Colonoscopy offers incomplete protection from colorectal cancer, particularly in the right colon. Part of this inadequacy may be related to serrated neoplasia. Serrated polyps of the colorectum are now understood to be a heterogeneous group of polyps, some of which are cancer precursors, such as the sessile serrated adenoma (SSA) and the traditional serrated adenoma (TSA). In contrast to conventional adenomas, there is limited published literature on the epidemiology and natural history of these lesions. Furthermore, existing guidelines regarding screening and surveillance practices for these polyps are based largely on expert opinion without firm evidence. In this review, we describe the current understanding of the molecular biology, histopathology, and endoscopic features of serrated neoplasia of the colorectum, with an emphasis on aspects relevant to the practicing gastroenterologist.

Colorectal advanced neoplasms occur through dual carcinogenesis pathways in individuals with coexisting serrated polyps

Background

Individuals with serrated polyps (SP) are at higher risk for synchronous colorectal advanced neoplasms (AN) and cancers. However, it remains unclear whether there is a unique involvement of the serrated pathway and/or the classical adenoma-carcinoma sequence in this setting.

Methods

Colorectal ANs, which include tubular adenomas ≥10 mm, adenomas with villous histology, high-grade intraepithelial neoplasms, and cancers, were collected retrospectively. The groups included ANs with (AN+SP) or without (AN-only) coexisting SPs. Clinicopathological findings were compared between groups. BRAF and KRAS mutations in ANs and SPs, and methylation levels at long interspersed element-1 (LINE-1) in adjacent mucosa were determined by pyrosequencing.

Results

Seventy-five ANs from 40 patients in the AN+SP group, and 179 ANs from 119 patients in the AN-only group were analyzed. There were no significant differences in clinicopathological findings between the two groups, except that intraepithelial neoplasia in the AN+SP group was more likely to be located in the right colon (P = 0.018). BRAF mutations were significantly more frequent in the AN+SP group (P = 0.003), while KRAS mutations showed no significant differences between groups (P = 0.142). The majority of high-grade intraepithelial neoplasms in both groups showed a contiguous component of conventional adenoma. Individuals with large and right-sided SPs had significantly more conventional adenomas compared to those without such SPs (P = 0.027 and P = 0.031, respectively). Adjacent mucosa from individuals with multiple and large SPs showed significantly lower methylation levels at LINE-1 compared to individuals without such associated SPs (P = 0.049 and P = 0.015, respectively).

Conclusion

Our data suggest that both the adenoma-carcinoma sequence and the serrated pathway are operational in individuals with coexisting ANs and SPs. The reduced methylation levels at LINE-1 in the background mucosa suggest the possibility of an underlying ‘field defect’.

Serrated polyps detected during screening colonoscopies

AIM OF THE STUDY

It is estimated that between 15% and 35% of sporadic colorectal cancers (CRC) developing from adenomas come from serrated polyps. Currently, the most effective method used to prevent CRC is the removal of adenomas, including serrated polyps, during colonoscopy. The aim of this paper is to analyze the changes characterized as serrated polyps and detected during screening colonoscopies performed as part of the Screening Program for Early Colorectal Cancer Detection (SPED).

MATERIAL AND METHODS

In our center, as part of the nationwide SPED between 2000 and 2009, 1,442 screening colonoscopies were performed.

RESULTS

Serrated polyps were found in 11.9% of all patients and in 45.8% of patients who had polyps removed by endoscopy. In screening colonoscopy of the large intestine, the following polyps were found most frequently: hyperplastic, < 1 cm, without a stalk, multiple, located in the distal part of the large intestine, in men and in patients with a first-degree relative with a history of abdominal cancer. Detecting and removing polyps was facilitated by the fact that the cecum was intubated and the bowel preparation had been performed either very well or well. The detection rate of serrated polyps was not influenced by patients' place of residence or their age.

CONCLUSIONS

Serrated polyps constitute a frequent, and very frequent among removed polyps, abnormality detected during screening colonoscopy.

Metachronous serrated neoplasia is uncommon after right colectomy in patients with methylator colon cancers with a high degree of microsatellite instability

BACKGROUND

Right-sided serrated polyps are precursors to sporadic microsatellite unstable colon cancers via the methylator pathway and have a high rate of synchronous and metachronous lesions. Serrated polyps also occur in Lynch syndrome, where right-sided microsatellite unstable cancers arise from germline mutations in mismatch repair genes.

OBJECTIVE

The aim of this study was to compare serrated neoplasia in patients with sporadic and hereditary microsatellite unstable colon cancer and to examine the effect of right colectomy on the risk of metachronous polyps and cancers.

DESIGN

This is a retrospective, descriptive, cohort study from database and chart review.

SETTING

This study was conducted at a tertiary care hospital with a center for hereditary colorectal cancer.

PATIENTS

Patients who had colon cancers with a high degree of microsatellite instability, methylator cancers, and Lynch syndrome cancers, were included.

INTERVENTIONS

Interventions included colectomy, surveillance colonoscopy, and polypectomy.

MAIN OUTCOME MEASURES

The primary outcomes measured were the incidence and location of metachronous polyps and cancers.

RESULTS

Eighty-five patients were included: 47 with methylator cancers and 38 with Lynch syndrome. Median ages at surgery were 75 years (range, 41-90) and 48 years (range, 27-77), p < 0.0001. Forty-six (98%) patients with methylator cancers and 17 (45%) patients with Lynch syndrome underwent a right colectomy, p < 0.0001. Metachronous cancers occurred in 19/60 (32%) of patients with Lynch syndrome and no patients with methylator cancers, p < 0.0001. Thirty-four patients with methylator cancers had colonoscopic follow-up, with a median of 2 colonoscopies per patient over a 32-month follow-up (range, 1-136). Sixty-three percent of patients with Lynch syndrome had colonoscopic follow-up, median of 4 colonoscopies per patient over 102 months (range, 1-462), p < 0.0001. Four (9%) patients with methylator cancers each had 1 metachronous serrated polyp, compared with 10/37 (27%) patients with Lynch syndrome (p = 0.049), whose median number of polyps was 2 (range, 1-8). Characteristics of other associated polyps were similar between cohorts.

LIMITATIONS

This study is somewhat limited by potential inherent bias from its retrospective design. Also, a high number of deaths in the CIMP+ cohort could have contributed to the low number of serrated polyps detected on colonoscopy surveillance, but given current understanding of serrated polyp growth, this may truly represent the left colon's tendency not to develop serrated polyps.

CONCLUSIONS

Cancers with a high degree of microsatellite instability arise through 2 different molecular mechanisms. Metachronous serrated neoplasia, benign and malignant, following right colectomy in patients with the CpG-island methylator phenotype of colorectal cancer is uncommon. However, the colons of patients with Lynch syndrome are at high risk after segmental colectomy.

Gene expression profiling of serrated polyps identifies annexin A10 as a marker of a sessile serrated adenoma/polyp

Sessile serrated adenomas/polyps (SSA/Ps) are precursors of colon cancer, particularly those that exhibit microsatellite instability. Distinguishing SSA/Ps from the related, but innocuous, microvesicular hyperplastic polyp (MVHP) can be challenging. In this study seven gastrointestinal pathologists reviewed 109 serrated polyps and identified 60 polyps with histological consensus. Microarray analysis was performed on six distal consensus MVHPs < 9 mm, six proximal consensus SSA/Ps > 9 mm, and six normal colon biopsies (three proximal, three distal). Comparative gene expression analysis confirmed the close relationship between SSA/Ps and MVHPs as there was overlapping expression of many genes. However, the gene expression profile in SSA/Ps had stronger and more numerous associations with cancer-related genes compared with MVHPs. Three genes (TFF2, FABP6, and ANXA10) were identified as candidates whose expression can differentiate SSA/Ps from MVHPs, and the differences in expression were confirmed by quantitative RT-PCR. As ANXA10 showed the most promise in differentiating these polyps, the expression of ANXA10 was evaluated by immunohistochemistry in consensus SSA/Ps (n = 26), MVHPs (n = 21), and normal colon (n = 9). Immunohistochemical expression of ANXA10 was not identified in separate samples of normal colon or in the normal colonic epithelium adjacent to the serrated polyps. Consistent with the microarray and quantitative RT-PCR experiments, immunohistochemical expression of ANXA10 was markedly increased in SSA/Ps compared to MVHPs (p < 0.0001). An ANXA10 score ≥ 3 has a sensitivity of 73% and a specificity of 95% in the diagnosis of an SSA/P. In conclusion, we show that SSA/Ps and MVHPs have significant overlap in gene expression, but also important differences, particularly in cancer-related pathways. Expression of ANXA10 may be a potential marker of the serrated pathway to colon cancer.

Serrated colon polyps as precursors to colorectal cancer

Identification of the serrated neoplasia pathway has improved our understanding of the pathogenesis of colorectal cancer (CRC). Insights include an increased recognition of the malignant potential of different types of serrated polyps such as sessile and traditional serrated adenomas. Sessile serrated adenomas share molecular features with colon tumors that have microsatellite instability and a methylator phenotype, indicating that these lesions are precursors that progress via the serrated neoplasia pathway. These data have important implications for clinical practice and CRC prevention, because hyperplastic polyps were previously regarded as having no malignant potential. There is also evidence that the serrated pathway contributes to interval or missed cancers. Endoscopic detection of serrated polyps is a challenge because they are often inconspicuous with indistinct margins and are frequently covered by adherent mucus. It is important for gastroenterologists to recognize the subtle endoscopic features of serrated polyps to facilitate their detection and removal, and thereby ensure a high-quality colonoscopic examination. Recognition of the role of serrated polyps in colon carcinogenesis has led to the inclusion of these lesions in postpolypectomy surveillance guidelines. However, an enhanced effort is needed to identify and completely remove serrated adenomas, with the goal of increasing the effectiveness of colonoscopy to reduce CRC incidence.

Paneth cells in colonic adenomas: association with male sex and adenoma burden

Paneth cells have been reported in colorectal adenomas and adenocarcinomas; however, the frequency of colonic Paneth cell-containing adenomas is unknown as are their clinicopathologic features. A total of 152 consecutive colorectal adenomas from 103 patients (57 males and 46 females) were reviewed. The frequency of Paneth cells in this cohort of adenomas was determined and correlated with patient demographics. Twenty-six adenomas (17.1%) from 22 (21.4%) patients harbored Paneth cells, which were not limited to the base of the crypts but aberrantly located throughout the crypts. Patient age, adenoma size, villous features, and grade of dysplasia were not different between these 2 groups. Not surprisingly, Paneth cell-containing adenomas were more likely to occur in the proximal colon (84.6% vs. 55.6%; P=0.006). There was a strong association between male sex and Paneth cell-containing adenomas, as 23 of 26 (88.5%) of these adenomas occurred in male individuals compared with 71 of 126 (56.3%) non-Paneth cell-containing adenomas (P=0.002). Upon review of an additional 460 adenomas from 200 patients with varying numbers of adenomas (68 with 1 adenoma, 68 with 2 adenomas, and 64 with 3 or more adenomas), the risk of harboring synchronous adenomas was associated with villous morphology, proximal location, and the presence of a Paneth cell-containing adenoma. Thus, the presence of a Paneth cell-containing adenoma may be a marker for increased risk of developing colorectal neoplasia.

Colorectal carcinoma: Pathologic aspects

Colorectal carcinoma is one of the most common cancers and one of the leading causes of cancer-related death in the United States. Pathologic examination of biopsy, polypectomy and resection specimens is crucial to appropriate patient managemnt, prognosis assessment and family counseling. Molecular testing plays an increasingly important role in the era of personalized medicine. This review article focuses on the histopathology and molecular pathology of colorectal carcinoma and its precursor lesions, with an emphasis on their clinical relevance.

Serrated lesions of the colorectum: review and recommendations from an expert panel

Serrated lesions of the colorectum are the precursors of perhaps one-third of colorectal cancers (CRCs). Cancers arising in serrated lesions are usually in the proximal colon, and account for a disproportionate fraction of cancer identified after colonoscopy. We sought to provide guidance for the clinical management of serrated colorectal lesions based on current evidence and expert opinion regarding definitions, classification, and significance of serrated lesions. A consensus conference was held over 2 days reviewing the topic of serrated lesions from the perspectives of histology, molecular biology, epidemiology, clinical aspects, and serrated polyposis. Serrated lesions should be classified pathologically according to the World Health Organization criteria as hyperplastic polyp, sessile serrated adenoma/polyp (SSA/P) with or without cytological dysplasia, or traditional serrated adenoma (TSA). SSA/P and TSA are premalignant lesions, but SSA/P is the principal serrated precursor of CRCs. Serrated lesions have a distinct endoscopic appearance, and several lines of evidence suggest that on average they are more difficult to detect than conventional adenomatous polyps. Effective colonoscopy requires an endoscopist trained in the endoscopic appearance of serrated lesions. We recommend that all serrated lesions proximal to the sigmoid colon and all serrated lesions in the rectosigmoid > 5 mm in size, be completely removed. Recommendations are made for post-polypectomy surveillance of serrated lesions and for surveillance of serrated polyposis patients and their relatives.

Colorectal carcinoma: Pathologic aspects

Colorectal carcinoma is one of the most common cancers and one of the leading causes of cancer-related death in the United States. Pathologic examination of biopsy, polypectomy and resection specimens is crucial to appropriate patient managemnt, prognosis assessment and family counseling. Molecular testing plays an increasingly important role in the era of personalized medicine. This review article focuses on the histopathology and molecular pathology of colorectal carcinoma and its precursor lesions, with an emphasis on their clinical relevance.

Failure to recognize serrated polyposis syndrome in a cohort with large sessile colorectal polyps

BACKGROUND

Serrated polyposis syndrome (SPS) is a rare condition of multiple serrated colorectal polyps and cancers. Colorectal cancer risk is increased in SPS.

OBJECTIVE

We determined the prevalence of SPS in a cohort of patients with large (≥ 2 cm) sessile colorectal polyps and the rate at which the diagnosis was made by the clinicians.

DESIGN

Review of patient care database. The 2010 World Health Organization (WHO) criteria were used to identify cases of SPS.

SETTING

Tertiary academic center.

PATIENTS

529 consecutive patients referred for endoscopic resection of a sessile colorectal polyp ≥ 2 cm.

MAIN OUTCOME MEASUREMENTS

Prevalence of SPS in the cohort and frequency with which the referring physician and the endoscopist recognized SPS.

RESULTS

Of the 529 patients, 20 (4%) met the WHO criteria for SPS. Only 1 of these cases was suspected by a referring physician. Twelve cases (60%) were either diagnosed or suspected by the endoscopist at our center. Compared with all other patients without SPS, those with SPS were more likely to have an index lesion (the lesion that led to referral) that was serrated (60% vs 3.8%), to have a cecal or ascending colon index lesion (70% vs 45%), and to be current smokers (42% vs 15%). Including the first colonoscopy to remove the index lesion and 26 follow-up colonoscopies, the endoscopist at our center removed 183 serrated polyps from the 20 patients with SPS; of those polyps, 68 were >1 cm. Three patients were referred for surgical resection of involved colon. Eighteen of the 20 patients with SPS met the WHO criterion of 5 serrated polyps proximal to the sigmoid, of which 2 are >1 cm. Failure to recognize SPS by the referring physician was at least partly related to unrecognized serrated lesions. Failure to recognize SPS by the endoscopist at our institution was the result of not systematically applying WHO criteria to the polyp findings.

LIMITATIONS

Retrospective study.

CONCLUSIONS

SPS was common in a cohort of patients with large sessile colorectal polyps, and it was frequently unrecognized. These data suggest the need for better detection of serrated lesions, better awareness of SPS, and more consistent application of SPS criteria to the polyp findings of individual patients.

Editorial: sessile serrated adenomas and their pit patterns: we must first see the forest through the trees

Serrated lesions of the colorectum include hyperplastic polyps, which are non-neoplastic, and sessile serrated adenomas (SSAs, also known as sessile serrated polyps) and traditional serrated adenomas, which are premalignant. It is believed that up to 30% of colon cancers and many post-colonoscopy cancers arise from serrated neoplasms. Post-colonoscopy cancers have been found to have a molecular signature similar to SSAs, including CpG island methylation, BRAF mutations, and microsatellite instability. A novel pit pattern, Type II-O, has been demonstrated to have a high specificity for SSAs. Unfortunately, the sensitivity is too low to utilize a Type II-O pit pattern to determine which serrated lesion is neoplastic and needs resection. Moreover, there is significant endoscopist-related variability in the detection of serrated lesions of the colon. Efforts to improve the detection of serrated neoplasms are warranted.