Pathological features associated with metastasis in patients with early invasive (pT1) colorectal carcinoma in colorectal polyps

Pitfalls during histological assessment in locally resected pT1 colorectal cancer

Colorectal cancer (CRC) is a common malignancy worldwide, and the stage of the tumour is closely related to clinical outcome. Bowel cancer screening programmes have resulted in the identification of colorectal cancer at earlier stages. Approximately 10% of patients with the earliest stage of CRC (i.e. pT1) will possess regional lymph node metastases (LNM). Therefore, if these patients have initially been treated by local resection (e.g. polypectomy), this subgroup will require surgical resection. Identification of pathological risk factors for LNM within locally resected pT1 CRC is a very important process during the histological assessment of these lesions. This paper describes the most commonly encountered and clinically significant difficulties in the histological assessment of these cases. These pitfalls are illustrated using four examples of locally resected pT1 CRC that were received by our department during routine diagnostic practice.

Interobserver agreement and practice patterns for grading of colorectal carcinoma: World Health Organization (WHO) classification of tumours 5th edition versus American Joint Committee on Cancer (AJCC) 8th edition staging manual

AIMS

The current American Joint Committee on Cancer (AJCC) staging manual and the College of American Pathologists (CAP) colorectal carcinoma (CRC) protocol specify use of a four-tiered grading system (i.e. grades 1-4; well-differentiated-undifferentiated) for CRC, based on percentage of gland formation. The World Health Organization (WHO) 5th edition grades CRC into low-grade (well- and moderately differentiated) and high-grade (poorly and undifferentiated), based on the least differentiated component. We studied interobserver agreement and practice patterns among pathologists when grading CRC by these two grading systems.

METHODS AND RESULTS

Five gastrointestinal pathologists reviewed 100 scanned CRC slides and graded the tumour on each slide, per provided criteria in (a) WHO 5th edition book, (b) AJCC manual/CAP CRC protocol and (c) their clinical practice. A questionnaire for grading selected CRC subtypes was also provided. Statistical analysis was performed using Pearson's χ2 test and Fleiss multi-rater kappa analyses. Overall, agreement among the five reviewers when grading via WHO and AJCC criteria for low-grade and high-grade CRC was moderate (κ = 0.568, P < 0.001) and good (κ = 0.611, P < 0.001), respectively. All reviewers graded significantly more tumours as high-grade when using WHO (median = 46) versus AJCC/CAP criteria (median = 20).

CONCLUSIONS

Interobserver agreement was higher using the AJCC grading criteria as a two-tiered system. Significantly more tumours were called high-grade using the WHO criteria. This raises concerns regarding upgrading tumours, as well as potential differences in grading tumours among pathologists worldwide, based on regional preferred grading systems. Synchronisation of these two grading systems is necessary for uniform grading of CRCs throughout institutions.

Significant variation in the assessment and management of screen-detected colorectal polyp cancers

PURPOSE

Endoscopic resection is appropriate for selected colorectal polyp cancers, but significant variation exists in treatment. This study aims to investigate variation in management of screen-detected polyp cancers (T1), factors predicting primary endoscopic polypectomy and threshold for subsequent surgical resection.

METHOD

Patients with polyp cancers (T1) diagnosed by the bowel cancer screening programme (BCSP) were investigated at two screening centres (5 individual sites and 4 MDTs, 2012-2022). Patient demographics, pathological characteristics, management and outcomes were recorded. Variation in management was compared between sites. Risk factors for primary endoscopic polypectomy and the need for subsequent surgical resection were analysed using multivariable binary logistic regression models.

RESULTS

Of 220 polyp cancers, 178 (81%) underwent primary endoscopic resection. Secondary surgical excision was required in 54 (30%). Study sites were not significantly different in their primary management for colonic or rectal polyps. Only the size of colonic polyps was associated with primary surgery rather than endoscopic polypectomy (OR 1.05 (95% CI 1.00-1.11); p = 0.038). There was a difference between study sites in the odds ratio for secondary surgery after primary polypectomy for colonic polyps (OR 3.97 (95% CI 1.20-16.0); p = 0.033) but not rectal. Other factors associated with the requirement for secondary surgery were as follows: sessile morphology for colonic polyps (OR 2.92 (95% CI 1.25-6.97); p = 0.013) and en-bloc resection for rectal polyps (OR 0.14 (0.02-0.85); p = 0.043).

CONCLUSION

There was significant variation in the assessment and treatment of colonic polyp cancers. Standardising pathology reporting and treatment algorithms may lead to better consistency of care and a reduction in secondary surgery.

Risk assessment in pT1 colorectal cancer

Colorectal cancer (CRC) is a common malignancy worldwide and tumour stage is closely related to clinical outcome. A small but significant proportion of submucosal-invasive (ie, pT1) CRC are associated with regional lymph node metastases (LNM) and a worse prognosis. The likelihood of LNM in pT1 CRC needs to be balanced against the operative risk and costs of surgical resection when determining the best patient management. A wide range of histopathological and clinical factors may affect LNM risk in this setting. This script provides a comprehensive overview of the tumour and patient-associated features that have been linked to LNM risk in pT1 CRC. Some of the features are well established within the literature and are included in published guidelines, while others are novel and emerging in nature. Odds ratios for LNM that are associated with key predictive features are provided where appropriate, and published models developed as an aid to the calculation of LNM risk are discussed.

Sporadic Polyps of the Colorectum

Colorectal polyps are common, and their diagnosis and classification represent a major component of gastrointestinal pathology practice. The majority of colorectal polyps represent precursors of either the chromosomal instability or serrated neoplasia pathways to colorectal carcinoma. Accurate reporting of these polyps has major implications for surveillance and thus for cancer prevention. In this review, we discuss the key histologic features of the major colorectal polyps with a particular emphasis on diagnostic pitfalls and areas of contention.

Machine Learning and Radiomics Analysis for Tumor Budding Prediction in Colorectal Liver Metastases Magnetic Resonance Imaging Assessment

PURPOSE

We aimed to assess the efficacy of machine learning and radiomics analysis using magnetic resonance imaging (MRI) with a hepatospecific contrast agent, in a pre-surgical setting, to predict tumor budding in liver metastases.

METHODS

Patients with MRI in a pre-surgical setting were retrospectively enrolled. Manual segmentation was made by means 3D Slicer image computing, and 851 radiomics features were extracted as median values using the PyRadiomics Python package. Balancing was performed and inter- and intraclass correlation coefficients were calculated to assess the between observer and within observer reproducibility of all radiomics extracted features. A Wilcoxon-Mann-Whitney nonparametric test and receiver operating characteristics (ROC) analysis were carried out. Balancing and feature selection procedures were performed. Linear and non-logistic regression models (LRM and NLRM) and different machine learning-based classifiers including decision tree (DT), k-nearest neighbor (KNN) and support vector machine (SVM) were considered.

RESULTS

The internal training set included 49 patients and 119 liver metastases. The validation cohort consisted of a total of 28 single lesion patients. The best single predictor to classify tumor budding was original_glcm_Idn obtained in the T1-W VIBE sequence arterial phase with an accuracy of 84%; wavelet_LLH_firstorder_10Percentile was obtained in the T1-W VIBE sequence portal phase with an accuracy of 92%; wavelet_HHL_glcm_MaximumProbability was obtained in the T1-W VIBE sequence hepatobiliary excretion phase with an accuracy of 88%; and wavelet_LLH_glcm_Imc1 was obtained in T2-W SPACE sequences with an accuracy of 88%. Considering the linear regression analysis, a statistically significant increase in accuracy to 96% was obtained using a linear weighted combination of 13 radiomic features extracted from the T1-W VIBE sequence arterial phase. Moreover, the best classifier was a KNN trained with the 13 radiomic features extracted from the arterial phase of the T1-W VIBE sequence, obtaining an accuracy of 95% and an AUC of 0.96. The validation set reached an accuracy of 94%, a sensitivity of 86% and a specificity of 95%.

CONCLUSIONS

Machine learning and radiomics analysis are promising tools in predicting tumor budding. Considering the linear regression analysis, there was a statistically significant increase in accuracy to 96% using a weighted linear combination of 13 radiomics features extracted from the arterial phase compared to a single radiomics feature.

Lymph Node Molecular Analysis with OSNA Enables the Identification of pT1 CRC Patients at Risk of Recurrence: A Multicentre Study

Early-stage colorectal carcinoma (CRC)-pT1-is a therapeutic challenge and presents some histological features related to lymph node metastasis (LNM). A significant proportion of pT1 CRCs are treated surgically, resulting in a non-negligible surgical-associated mortality rate of 1.5-2%. Among these cases, approximately 6-16% exhibit LNM, but the impact on survival is unclear. Therefore, there is an unmet need to establish an objective and reliable lymph node (LN) staging method to optimise the therapeutic management of pT1 CRC patients and to avoid overtreating or undertreating them. In this multicentre study, 89 patients with pT1 CRC were included. All histological features associated with LNM were evaluated. LNs were assessed using two methods, One-Step Nucleic Acid Amplification (OSNA) and the conventional FFPE plus haematoxylin and eosin (H&E) staining. OSNA is an RT-PCR-based method for amplifying CK19 mRNA. Our aim was to assess the performance of OSNA and H&E in evaluating LNs to identify patients at risk of recurrence and to optimise their clinical management. We observed an 80.9% concordance in LN assessment using the two methods. In 9% of cases, LNs were found to be positive using H&E, and in 24.7% of cases, LNs were found to be positive using OSNA. The OSNA results are provided as the total tumour load (TTL), defined as the total tumour burden present in all the LNs of a surgical specimen. In CRC, a TTL ≥ 6000 CK19 m-RNA copies/µL is associated with poor prognosis. Three patients had TTL > 6000 copies/μL, which was associated with higher tumour budding. The discrepancies observed between the OSNA and H&E results were mostly attributed to tumour allocation bias. We concluded that LN assessment with OSNA enables the identification of pT1 CRC patients at some risk of recurrence and helps to optimise their clinical management.