The third pathway of colorectal carcinogenesis

The histologic features, molecular features, detection and management of serrated polyps: a review

The serrated pathway to colorectal cancers (CRCs) is a significant pathway encompassing five distinct types of lesions, namely hyperplastic polyps (HPs), sessile serrated lesions (SSLs), sessile serrated lesions with dysplasia (SSL-Ds), traditional serrated adenomas (TSAs), and serrated adenoma unclassified. In contrast to the conventional adenoma-carcinoma pathway, the serrated pathway primarily involves two mechanisms: BRAF/KRAS mutations and CpG island methylator phenotype (CIMP). HPs are the most prevalent non-malignant lesions, while SSLs play a crucial role as precursors to CRCs, On the other hand, traditional serrated adenomas (TSAs) are the least frequently encountered subtype, also serving as precursors to CRCs. It is crucial to differentiate these lesions based on their unique morphological characteristics observed in histology and colonoscopy, as the identification and management of these serrated lesions significantly impact colorectal cancer screening programs. The management of these lesions necessitates the crucial steps of removing premalignant lesions and implementing regular surveillance. This article provides a comprehensive summary of the epidemiology, histologic features, molecular features, and detection methods for various serrated polyps, along with recommendations for their management and surveillance.

Prognostic Biomarkers of Cell Proliferation in Colorectal Cancer (CRC): From Immunohistochemistry to Molecular Biology Techniques

Colorectal cancer (CRC) is one of the most common and severe malignancies worldwide. Recent advances in diagnostic methods allow for more accurate identification and detection of several molecular biomarkers associated with this cancer. Nonetheless, non-invasive and effective prognostic and predictive testing in CRC patients remains challenging. Classical prognostic genetic markers comprise mutations in several genes (e.g., APC, KRAS/BRAF, TGF-β, and TP53). Furthermore, CIN and MSI serve as chromosomal markers, while epigenetic markers include CIMP and many other candidates such as SERP, p14, p16, LINE-1, and RASSF1A. The number of proliferation-related long non-coding RNAs (e.g., SNHG1, SNHG6, MALAT-1, CRNDE) and microRNAs (e.g., miR-20a, miR-21, miR-143, miR-145, miR-181a/b) that could serve as potential CRC markers has also steadily increased in recent years. Among the immunohistochemical (IHC) proliferative markers, the prognostic value regarding the patients' overall survival (OS) or disease-free survival (DFS) has been confirmed for thymidylate synthase (TS), cyclin B1, cyclin D1, proliferating cell nuclear antigen (PCNA), and Ki-67. In most cases, the overexpression of these markers in tissues was related to worse OS and DFS. However, slowly proliferating cells should also be considered in CRC therapy (especially radiotherapy) as they could represent a reservoir from which cells are recruited to replenish the rapidly proliferating population in response to cell-damaging factors. Considering the above, the aim of this article is to review the most common proliferative markers assessed using various methods including IHC and selected molecular biology techniques (e.g., qRT-PCR, in situ hybridization, RNA/DNA sequencing, next-generation sequencing) as prognostic and predictive markers in CRC.

Whole exome sequencing of a gut-associated lymphoid tissue neoplasm points to precursor or early form of sporadic colon carcinoma

Gut-associated lymphoid tissue (GALT) carcinoma is a colorectal neoplasm characterized by cystically dilated neoplastic glands that extend into prominent, well-circumscribed submucosal lymphoid tissue. Although often subtle, lamina propria between and around the neoplastic glands (identified by plasma cells, scattered eosinophils, etc.) is frequent in cases with classic morphology, arguing (at least in such cases) in favor of adenoma extending into lymphoglandular complexes rather than true invasive carcinoma. Some have postulated that the tumor arises from M-cells, specialized epithelial cells overlying GALT, and others have suggested it represents a unique pathway to carcinoma, specific to the environmental conditions of epithelium overlying lymphoid tissue. Although both hypotheses are intriguing, definitive phenotypic and genetic support is currently lacking. To address these possibilities, we undertook whole exome sequencing and immunohistochemical characterization of a GALT neoplasm recently identified on our clinical service. We discovered well-known mutations in both APC and KRAS, as well as mutations in several Wnt pathway components (MED12, BCL9L, RFX4, DACT3). No immunohistochemical expression of GP2, a marker of M-cell differentiation, was identified. Expression of CDX2, SATB2, and the DNA mismatch repair proteins was observed, while expression of both CK7 and CK20 was absent. No PD-L1 expression was present on tumor cells, but PD-L1 expression was noted in a subset of tumor-adjacent mononuclear cells. Overall, the findings suggest that GALT neoplasms, although morphologically distinct, may be a precursor or early form of typical sporadic colon carcinoma.

Colorectal epithelial neoplasm associated with gut-associated lymphoid tissue

BACKGROUND

Colorectal epithelial neoplasm extending into the submucosal gut-associated lymphoid tissue (GALT) can cause difficulties in the differential diagnosis. Regarding GALT-associated epithelial neoplasms, a few studies favor the term "GALT carcinoma" while other studies have mentioned the term "GALT-associated pseudoinvasion/epithelial misplacement (PEM)".

METHODS

The clinicopathologic characteristics of 11 cases of colorectal epithelial neoplasm associated with submucosal GALT diagnosed via endoscopic submucosal dissection were studied.

RESULTS

Eight cases (72.7%) were in males. The median age was 59 years, and age ranged from 53 to 73. All cases had a submucosal tumor component more compatible with GALT-associated PEM. Eight cases (72.7%) were located in the right colon. Ten cases (90.9%) had a non-protruding endoscopic appearance. Nine cases (81.8%) showed continuity between the submucosal and surface adenomatous components. Nine cases showed (81.8%) focal defects or discontinuation of the muscularis mucosae adjacent to the submucosal GALT. No case showed hemosiderin deposits in the submucosa or desmoplastic reaction. No case showed single tumor cells or small clusters of tumor cells in the submucosal GALT. Seven cases (63.6%) showed goblet cells in the submucosa. No cases showed oncocytic columnar cells lining submucosal glands.

CONCLUSIONS

Our experience suggests that pathologists should be aware of the differential diagnosis of GALT-associated submucosal extension by colorectal adenomatous neoplasm. Further studies are needed to validate classification of GALT-associated epithelial neoplasms.

Impact of an optimized colonoscopic screening program for patients with Lynch syndrome: 6-year results of a specialized French network

BACKGROUND

Despite colonoscopic screening, colorectal cancer (CRC) remains frequent in patients with Lynch syndrome (LS). The objective of this study was to evaluate the impact of an optimized colorectal screening program within a French dedicated network.

METHODS

All LS patients followed at our institution were consecutively included in the Prédisposition au Cancer Colorectal-Ile de France (PRED-IdF) network. Patients were offered an optimized screening program allowing an adjustment of the interval between colonoscopies, depending on bowel preparation, chromoendoscopy achievement and adenoma detection. Colonoscopies were defined as optimal when all the screening criteria were respected. We compared colonoscopy quality and colonoscopy detection rate before and after PRED-IdF inclusion, including polyp detection rate (PDR), adenoma detection rate (ADR) and cancer detection rate (CDR).

RESULTS

Between January 2010 and January 2016, 144 LS patients were consecutively included (male/female = 50/94, mean age = 51 ± 13 years and mutations: MLH1 = 39%, MSH2 = 44%, MSH6 = 15%, PMS2 = 1%). A total of 564 colonoscopies were analyzed, 353 after inclusion and 211 before. After PRED-IdF inclusion, 98/144 (68%) patients had optimal screening colonoscopies versus 33/132 (25%) before (p < 0.0005). The optimal colonoscopy rate was 304/353 (86%) after inclusion versus 87/211 (41%) before, (p < 0.0001). PRED-IdF inclusion was associated with a reduction of CRC occurrence with a CDR of 1/353 (0.3%) after inclusion versus 6/211 (2.8%) before (p = 0.012). ADR and PDR were 99/353 (28%) versus 60/211 (28.8%) (p > 0.05) and 167/353 (48.1%) versus 90/211 (42.2%) (p > 0.05), respectively after and before inclusion.

CONCLUSIONS

An optimized colonoscopic surveillance program in LS patients seems to improve colonoscopic screening quality and might possibly decrease colorectal interval cancer occurrence. Long-term cohort studies are needed to confirm these results.

GALT carcinoma: three case reports with glycoprotein 2 immunohistochemistry and electron microscopic observations

AIMS

Gut-associated lymphoid tissue (GALT) carcinoma is a rare colorectal tumour that arises in the epithelium covering GALT. GALT carcinoma is a differentiated tubular adenocarcinoma with dense lymphoid tissue with a characteristically well-demarcated margin. To date, 26 cases of GALT carcinoma, including the three cases discussed here, have been reported. Most (24 of 26) were discovered at early stages and none of the cases have documented any metastases. This suggests that GALT carcinoma may have a favourable prognosis. It is hypothesised that GALT carcinoma originates from M cells in specialised epithelia covering GALT. However, this hypothesis has yet to be confirmed.

METHODS AND RESULTS

In this study, we examined three cases of GALT carcinoma by immunohistochemistry detection of glycoprotein 2, a specific marker for M cells, and electron microscopy. Our findings showed that the tumour cells of GALT carcinoma in all three cases were negative for M cells. We thus concluded that GALT carcinoma may be a tubular adenocarcinoma arising by chance in the GALT. This unique carcinoma is a diferentiated adenocarcinoma that grows slowly with the development of GALT.

CONCLUSIONS

We propose that GALT carcinoma should be classified separately because of its histological setting and good prognosis.

Clinical significance of peripheral circulating tumor cell counts in colorectal polyps and non-metastatic colorectal cancer

Background

The presence of peripheral circulating tumor cells indicates the possible existence of a tumor in vivo; however, low numbers of circulating tumor cells (CTCs) can be detected in peripheral blood of healthy individuals as well as patients with benign tumors. It is not known whether peripheral CTC counts differ between patients with benign colorectal disease and those with colorectal cancer.

Methods

Comparative analysis of preoperative peripheral circulating tumor cells counts was completed in patients with benign colorectal disease (colorectal polyps) and non-metastatic cancer of the colon and rectum.

Results

The results of this analysis showed that patients with colorectal cancer had higher CTC counts than patients with colorectal polyps (3.47 ± 0.32/3.2 ml vs 1.49 ± 0.2/3.2 ml, P < 0.001). Colorectal cancer patients with tumors of the sigmoid colon displayed the highest CTC counts (4.87 ± 0.95/3.2 ml), followed by those with tumors of the rectum (3.73 ± 0.54/3.2 ml), ascending colon (3.5 ± 0.63/3.2 ml), transverse colon (2.4 ± 0.68/3.2 ml), and descending colon (2.08 ± 0.46/3.2 ml). Colorectal polyp patients with polyps in the rectum showed the highest CTC counts (2.2 ± 0.77/3.2 ml), followed by those with polyps in the ascending colon (1.82 ± 0.54/3.2 ml), sigmoid colon (1.38 ± 0.25/3.2 ml), transverse colon (0.75 ± 0.25/3.2 ml), and descending colon (0.33 ± 0.21/3.2 ml). The differences in CTC counts suggest that anatomical location of colorectal tumors may affect blood vessel metastasis. Meanwhile, patients with moderately differentiated and poorly differentiated tumors displayed higher peripheral blood CTC counts compared to those with well-differentiated tumors (P < 0.001). This result suggests that the type of tissue differentiation of colorectal tumors may act as another factor that affects blood vessel metastasis.

Conclusions

Circulating tumor cells can be detected in the peripheral blood of colorectal cancer patients as well as patients with colorectal polyps. The differences in CTC counts suggest that anatomical location and the type of tissue differentiation of colorectal tumors may affect blood vessel metastasis.