GNAS mutations are present in colorectal traditional serrated adenomas, serrated tubulovillous adenomas and serrated adenocarcinomas with adverse prognostic features

Significance of Micromorphological Characteristics and Expression of Intermediate Filament Proteins CK7 and CK20 in the Differential Diagnosis of Serrated Lesions of the Colorectum

Serrated lesions in the colorectum include all epithelial neoplastic lesions, which show a sawtooth-like morphology in the epithelial crypts. Classification systems nosologically divide colon serrated polyps into three different categories, primarily emphasizing their micromorphological growth pattern and cytodifferentiation: (1) hyperplastic polyps, (2) sessile serrated adenomas/polyps and (3) traditional serrated adenomas. Overall, 109 patients with serrated lesions of the colon, who underwent endoscopic or surgical polypectomy/tumorectomy during one or multiple endoscopic or surgical interventions, over a four-year period, were analyzed. The average age of patients was 62.8 ± 11.6 years. The frequency of serrated lesions of the colon in male patients was 2.4 times higher than in females (70.6% vs. 29.4%). All sessile serrated lesions without dysplasia were positive for CK7 and statistically significant compared to other serrated lesions, if this positivity was present in the complete crypt (p = 0.005). CK20 positivity, which is limited to the upper half of the crypt, is a special feature of hyperplastic polyps compared to other serrated lesions, which is statistically significant (p = 0.0078). Whereas, CK20 positivity of complete crypts is a statistically significant feature of traditional serrated adenomas (p < 0.01). Differences in the expression pattern of cytokeratin 7 and 20 in different serrated lesions may indicate different pathways of colorectal carcinogenesis, and be diagnostically and prognostically useful.

Colorectal adenosquamous carcinoma: genomic profiling of a rare histotype of colorectal cancer

Colorectal adenosquamous carcinoma (ASC) is exceedingly rare, comprising less than 0.1% of all colorectal malignancies, and is characterized by an aggressive disease course, with a higher metastatic rate and worse outcome than conventional colorectal adenocarcinoma. A comprehensive molecular profile of this group of neoplasms is still lacking. A total of 22 cases of colorectal ASCs (with 22 primary lesions and 7 metastases matched with 4 primaries) were subject to NGS targeting 67 cancer-related genes (VariantPlex solid tumor; Archer). Mismatch repair (MMR), p53, and ^V600EBRAF status were also investigated by immunohistochemistry. In 28 of 29 (96.6%) ASC samples, at least one single-nucleotide variant (SNV) or copy number variation (CNV) was detected. Among the 22 primary tumors, the most frequently mutated genes were TP53 (59.1%), APC (40.9%), KRAS (27.3%), BRAF (13.6%), and GNAS (9.1%). Only 1/22 (4.5%) primary ASC was MMR-deficient (MMRd) and harbored a BRAF mutation. Limited differences in SNVs were observed between primary and metastatic diseases. This study sheds light on the molecular landscape of colorectal ASCs. According to our data, the genomic profile of colorectal ASC is similar to that of conventional colorectal carcinoma, with significant druggable genetic alterations. Further studies are required to understand the more aggressive clinical behavior of this neoplasm.

A GNAS Gene Mutation's Independent Expression in the Growth of Colorectal Cancer: A Systematic Review and Meta-Analysis

Globally, colorectal carcinoma CRC is the third most common cancer and the third most common reason for cancer-associated mortality in both genders. The GNAS mutations are significantly linked with poor prognosis and failed treatment outcomes in CRC. A systematic review and meta-analysis of multiple studies executed following Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) criteria and registered with PROSPERO (registration number: CRD42021256452). The initial search includes a total of 271 publications; however, only 30 studies that merit the eligibility criteria were eventually chosen. Data analysis via OpenMeta Analyst and comprehensive meta-analysis 3.0 (CMA 3.0) software were used to investigate the prevalence of GNAS gene mutation among CRC patients. The meta-analysis consisted of 10,689 participants with most being males 6068/10,689 (56.8%). Overall, prevalence of GNAS mutations was 4.8% (95% CI: 3.1−7.3) with I2 = 94.39% and (p < 0.001). In 11/30 studies, the frequency of GNAS gene mutations was majorly in codons R201C [40.7% (95% CI: 29.2−53.2%)] and in codon R201H [39.7% (95% CI = 27.1−53.8)]. Overall prevalence of GNAS mutations was highest among the male gender: 53.9% (95% CI: 48.2−59.5%: I2 = 94.00%, (p < 0.001), tumour location (colon): 50.5% (95% CI: 33.2−67.6%: I2 = 97.93%, (p < 0.001), tumour grade (Well): 57.5% (95% CI: 32.4−79.2%: I2 = 98.10%, (p < 0.001) and tumour late stage: 67.9% (95% CI: 49.7−84.3%: I2 = 98.%, (p < 0.001). When stratified according to study location, a higher prevalence was observed in Japan (26.8%) while Italy has the lowest (0.4%). Overall prevalence of GNAS gene mutations was 4.8% with codons R201C and R201H being the most mutated, and the results conformed with numerous published studies on GNAS mutation.

Discovery of Long Non-Coding RNA MALAT1 Amplification in Precancerous Colorectal Lesions

A colorectal adenoma, an aberrantly growing tissue, arises from the intestinal epithelium and is considered as precursor of colorectal cancer (CRC). In this study, we investigated structural and numerical chromosomal aberrations in adenomas, hypothesizing that chromosomal instability (CIN) occurs early in adenomas. We applied array comparative genomic hybridization (aCGH) to fresh frozen colorectal adenomas and their adjacent mucosa from 16 patients who underwent colonoscopy examination. In our study, histologically similar colorectal adenomas showed wide variability in chromosomal instability. Based on the obtained results, we further stratified patients into four distinct groups. The first group showed the gain of MALAT1 and TALAM1, long non-coding RNAs (lncRNAs). The second group involved patients with numerous microdeletions. The third group consisted of patients with a disrupted karyotype. The fourth group of patients did not show any CIN in adenomas. Overall, we identified frequent losses in genes, such as TSC2, COL1A1, NOTCH1, MIR4673, and GNAS, and gene gain containing MALAT1 and TALAM1. Since long non-coding RNA MALAT1 is associated with cancer cell metastasis and migration, its gene amplification represents an important event for adenoma development.

The histomorphological and molecular landscape of colorectal adenomas and serrated lesions

The 2019 WHO classification of digestive system tumors significantly reformed the classificatory definition of serrated lesions of the colorectal mucosa and added new essential diagnostic criteria for both conventional adenomas and hereditary gastrointestinal polyposis syndromes. Histopathological examination of colorectal adenocarcinoma precursors lesions represents an important segment of daily clinical practice in a pathology department and is essential for the implementation of current colorectal adenocarcinoma secondary prevention strategies. This overview will focus on a schematic histopathological and molecular classification of precursor lesions arising within colorectal mucosa.

Spectrum of Somatic Cancer Gene Variations Among Adults With Appendiceal Cancer by Age at Disease Onset

IMPORTANCE

The incidence of appendiceal cancer (AC) is rising, particularly among individuals younger than 50 years (early-onset AC), with unexplained etiologies. The unique spectrum of somatic cancer gene variations among patients with early-onset AC is largely undetermined.

OBJECTIVE

To characterize the frequency of somatic variations and genomic patterns among patients with early-onset (age <50 years) vs late-onset (age ≥50 years) AC.

DESIGN, SETTING, AND PARTICIPANTS

This cohort study included individuals aged 18 years and older diagnosed with pathologically verified AC. Cases with clinical-grade targeted sequencing data from January 1, 2011, to December 31, 2019, were identified from the international clinicogenomic data-sharing consortium American Association for Cancer Research Project Genomics Evidence Neoplasia Information Exchange (GENIE). Data analysis was conducted from May to September 2020.

EXPOSURES

Age at disease onset.

MAIN OUTCOMES AND MEASURES

Somatic variation prevalence and spectrum in AC patients was determined. Variation comparisons between early-onset and late-onset AC were evaluated using multivariable logistic regression with adjustment for sex, race/ethnicity, histological subtype, sequencing center, and sample type.

RESULTS

In total 385 individuals (mean [SD] age at diagnosis, 56.0 [12.4] years; 187 [48.6%] men; 306 [79.5%] non-Hispanic White individuals) with AC were included in this study, and 109 patients (28.3%) were diagnosed with early-onset AC. Race/ethnicity differed by age at disease onset; non-Hispanic Black individuals accounted for a larger proportion of early-onset vs late-onset cases (9 of 109 [8.3%] vs 11 of 276 [4.0%]; P = 0.04). Compared with patients aged 50 years or older at diagnosis, patients with early-onset AC had significantly higher odds of presenting with nonsilent variations in PIK3CA, SMAD3, and TSC2 (PIK3CA: odds ratio [OR], 4.58; 95% CI, 1.72-12.21; P = .002; SMAD3: OR, 7.37; 95% CI, 1.24-43.87; P = .03; TSC2: OR, 12.43; 95% CI, 1.03-149.59; P = .047). In contrast, patients with early-onset AC had a 60% decreased odds of presenting with GNAS nonsilent variations compared with patients with late-onset AC (OR, 0.40; 95% CI, 0.21-0.76, P = .006). By histological subtype, young patients with mucinous adenocarcinomas of the appendix had 65% decreased odds of variations in GNAS compared with late-onset cases in adjusted models (OR, 0.35; 95% CI, 0.15-0.79; P = .01). Similarly, patients with early-onset nonmucinous appendiceal adenocarcinomas had 72% decreased odds of presenting with GNAS variations vs late-onset cases, although these findings did not reach significance (OR, 0.28; 95% CI, 0.07-1.14; P = .08). GNAS and TP53 variations were mutually exclusive in ACs among early-onset and late-onset cases (P < .05).

CONCLUSIONS AND RELEVANCE

In the study, AC diagnosed among younger individuals harbored a distinct genomic landscape compared with AC diagnosed among older individuals. Development of therapeutic modalities that target these unique molecular features may yield clinical implications specifically for younger patients.

Fibrous Dysplasia/McCune-Albright Syndrome: A Rare, Mosaic Disease of Gα s Activation

Fibrous dysplasia/McCune-Albright syndrome (FD/MAS) is a rare disorder of striking complexity. It arises from somatic, gain-of-function mutations in GNAS, leading to mosaic Gα s activation and inappropriate production of intracellular cyclic adenosine monophosphate (cAMP). The clinical phenotype is largely determined by the location and extent of affected tissues, and the pathophysiological effects of Gα s activation within these tissues. In bone, Gα s activation results in impaired differentiation of skeletal stem cells, leading to discrete skeletal lesions prone to fracture, deformity, and pain. Extraskeletal manifestations include a variable combination of hyperpigmented macules and hyperfunctioning endocrinopathies. Distinctive age-related changes in disease development has key effects on histologic, radiographic, and clinical features. FD/MAS thus presents along a uniquely broad clinical spectrum, and the resulting challenges in diagnosis and management can be difficult for clinicians. This review presents FD/MAS in the context of a mosaic disorder of Gα s activation, providing an intellectual framework within which to understand, evaluate, and treat this interesting disease. It includes a comprehensive summary of current understanding of FD/MAS pathogenesis, and a detailed discussion of clinical presentation and management. Critical areas of unmet need are highlighted, including discussion of key challenges and potential solutions to advance research and clinical care in FD/MAS.

Clinicopathological and molecular correlations in traditional serrated adenoma

BACKGROUND

Traditional serrated adenoma (TSA) is the least common type of colorectal serrated polyp, which exhibits considerable morphological and molecular diversity.

METHODS

We examined the spectra of alterations in MAPK and WNT pathway genes and their relationship with clinicopathological features in 128 TSAs.

RESULTS

Sequencing analyses identified BRAF V600E, BRAF non-V600E, KRAS, and NRAS mutations in 77, 3, 45, and 1 lesion, respectively. Collectively, 124 lesions (97%) had mutations in MAPK pathway genes. Alterations in WNT pathway genes were identified in 107 lesions (84%), including RSPO fusions/overexpression, RNF43 mutations, ZNRF3 mutations, APC mutations, and CTNNB1 mutations in 47, 45, 2, 13, and 2 lesions, respectively. Ten lesions (8%) harbored GNAS mutations. There was significant interdependence between the altered MAPK and WNT pathway genes. RSPO fusions/overexpression was significantly associated with KRAS mutations (31/47, 66%), whereas most RNF43 mutations coexisted with the BRAF V600E mutation (40/45, 89%). Histologically, extensive slit-like serration was more common in lesions with the BRAF V600E mutation (71%) and those with RNF43 mutations (87%). Prominent ectopic crypt formation was more prevalent in lesions with RSPO fusions/overexpression (58%) and those with GNAS mutations (100%).

CONCLUSIONS

Our observations indicate that TSAs mostly harbor various combinations of concurrent WNT and MAPK gene alterations. The associations between genetic and morphological features suggest that the histological diversity of TSA reflects the underlying molecular heterogeneity.

Traditional serrated adenoma: an overview of pathology and emphasis on molecular pathogenesis

Objective

To provide an overview of the pathology and molecular pathogenesis of traditional serrated adenomas (TSA).

Design

Describe the morphology and molecules that play a role in their pathogenesis.

Results

These exuberant polypoid lesions are typified by tall cells with deeply eosinophilic cytoplasm, elongated nuclei bearing delicate chromatin, ectopic crypt foci, deep clefting of the lining mucosa and an overall resemblance to small bowel mucosa.

Broadly, TSAs arise via three mechanisms. They may be BRAF mutated and CpG island methylator phenotype (CIMP)-high: right sided, mediated through a microvesicular hyperplastic polyp or a sessile serrated adenoma, may also have RNF43 mutations and result in microsatellite stable (MSS) colorectal cancers (CRC). The second pathway that is mutually exclusive of the first is mediated through KRAS mutation with CIMP-low TSAs. These are left-sided TSAs, are not associated with another serrated polyp and result in MSS CRC. These TSAs also have RSPO3, RNF43 and p53 mutations together with aberrant nuclear localisation of β-catenin. Third, there is a smaller group of TSAs that are BRAF and KRAS wild type and arise by as yet unknown molecular events. All TSAs show retention of mismatch repair proteins.

Conclusion

These are characteristic unusual polyps with a complex molecular landscape.