Heterogeneous mutational profile and prognosis conferred by TP53 mutations in appendiceal mucinous neoplasms

Progress in Biological Research and Treatment of Pseudomyxoma Peritonei

Pseudomyxoma peritonei (PMP) is a rare disease characterized by extensive peritoneal implantation and mass secretion of mucus after primary mucinous tumors of the appendix or other organ ruptures. Cytoreductive surgery (CRS) combined with hyperthermic intraperitoneal chemotherapy (HIPEC) is currently the preferred treatment, with excellent efficacy and safety, and is associated with breakthrough progress in long-term disease control and prolonged survival. However, the high recurrence rate of PMP is the key challenge in its treatment, which limits the clinical application of multiple rounds of CRS-HIPEC and does not benefit from conventional systemic chemotherapy. Therefore, the development of alternative therapies for patients with refractory or relapsing PMP is critical. The literature related to PMP research progress and treatment was searched in the Web of Science, PubMed, and Google Scholar databases, and a literature review was conducted. The overview of the biological research, treatment status, potential therapeutic strategies, current research limitations, and future directions associated with PMP are presented, focuses on CRS-HIPEC therapy and alternative or combination therapy strategies, and emphasizes the clinical transformation prospects of potential therapeutic strategies such as mucolytic agents and targeted therapy. It provides a theoretical reference for the treatment of PMP and the main directions for future research.

Clinicopathological spectrums and prognosis of primary appendiceal adenocarcinoma, goblet cell adenocarcinoma, and low-grade appendiceal mucinous neoplasms

Primary appendiceal adenocarcinoma (APCA), goblet cell adenocarcinoma (GCA), and low/high-grade appendiceal mucinous neoplasms (LAMN/HAMN) are distinct entities with overlapping clinical presentation and histomorphology, leading to diagnostic challenges. We retrospectively reviewed our archived cases between 2010 and 2018 for diagnosis reappraisal and comparative analysis using updated terminology and modern parameters. A total of 87 cases (22 APCA, 40 GCA, and 25 LAMN pT≥3) were included. The entire cohort had 49 women and 38 men with a median age of 59.9 (range 26-88) years. There were no statistically significant differences in age and sex among the three groups. Clinically, patients with GCA were more likely to present with acute appendicitis (65%) and more likely to have appendectomy as initial surgery (68%). Both APCA and GCA were more likely to involve the proximal appendix while LAMN was more likely to involve the distal appendix (p<0.05). All APCAs were associated with mucosal precursor lesions, most commonly tubular, tubulovillous, or villous adenoma, flat LAMN/HAMN-pTis mucinous epithelium, or mixed, which correlated with distinct histomorphology, tumour differentiation, and stage. Although polypoid precursor lesions were rare in GCA, a significant proportion of GCA showed crypt atypia associated with neoplastic cells. Immunohistochemically, APCA had more frequent β-catenin nuclear positivity and loss of SATB2 expression (p<0.05). KRAS mutation was more common in APCA than in GCA (8/11 vs 1/7, p<0.01). We further validated the three-tiered grading system (G1, G2, G3) in GCA, which correlated well with tumour stage and patient survival. APCA had worse progression-free and disease-specific survivals than GCA and LAMN (pT≥3) with the latter being relatively indolent even when perforated with peritoneal spread. Our study is the first comprehensive comparison between all three appendiceal neoplasms. We also describe a spectrum of previously under-recognised crypt atypia in GCA, which should trigger a diligent search for GCA if present.

The genetic profile and molecular subtypes of human pseudomyxoma peritonei and appendiceal mucinous neoplasms: a systematic review

Pseudomyxoma peritonei (PMP) is a rare, progressive, slowly growing neoplastic condition which is poorly understood, with a 5-year progression-free survival rate as low as 48%. PMP is most commonly caused by appendiceal mucinous neoplasms (AMN), and understanding their genetic biology and pathogenicity may allow for the development of better novel systemic treatments to target key deleterious mutations and the implicated pathways. The primary aim of this systematic review was to identify the genetic profile of histologically confirmed human PMP or AMN samples. The secondary aim was to identify whether genetic marks could be used to predict patient survival. Ovid EMBASE, Ovid MEDLINE, PubMed, and Web of Science were searched to identify studies investigating the genetic profile of histologically-confirmed human PMP or AMN samples. We review findings of 46 studies totalling 2181 tumour samples. The most frequently identified somatic gene mutations in patients with PMP included KRAS (38-100%), GNAS (17-100%), and TP53 (5-23%); however, there were conflicting results of their effect on survival. Three studies identified molecular subtypes based on gene expression profiles classifying patients into oncogene-enriched, immune-enriched, and mixed molecular subtypes with prognostic value. This review summarises the current literature surrounding genetic aberrations in PMP and AMNs and their potential utility for targeted therapy. Given the recent advances in clinical trials to directly target KRAS and GNAS mutations in other cancers, we propose a rationale to explore these mutations in future pre-clinical studies in PMP with a view for a future clinical trial.

Molecular and immunophenotypic characterization of anal squamous cell carcinoma reveals distinct clinicopathologic groups associated with HPV and TP53 mutation status

Squamous cell carcinoma (SqCC) is the most common malignancy of the anal canal, where it is strongly associated with HPV infection. Characteristic genomic alterations have been identified in anal SqCC, but their clinical significance and correlation with HPV status, pathologic features, and immunohistochemical markers are not well established. We examined the molecular and clinicopathologic features of 96 HPV-positive and 20 HPV-negative anal SqCC. HPV types included 89 with HPV16, 2 combined HPV16/HPV18, and 5 HPV33. HPV-positive cases demonstrated frequent mutations or amplifications in PIK3CA (30%; p = 0.027) or FBXW7 mutations (10%). HPV-negativity was associated with frequent TP53 (53%; p = 0.00001) and CDKN2A (21%; p = 0.0045) mutations. P16 immunohistochemistry was positive in all HPV-positive cases and 3/20 HPV-negative cases (p < 0.0001; sensitivity: 100%; specificity: 85%) and was associated with basaloid morphology (p = 0.0031). Aberrant p53 immunohistochemical staining was 100% sensitive and specific for TP53 mutation (p < 0.0001). By the Kaplan-Meier method, HPV-negativity, aberrant p53 staining, and TP53 mutation were associated with inferior overall survival (OS) (p < 0.0001, p = 0.0103, p = 0.0103, respectively) and inferior recurrence-free survival (p = 0.133, p = 0.0064, and p = 0.0064, respectively). TP53/p53 status stratified survival probability by HPV status (p = 0.013), with HPV-negative/aberrant p53 staining associated with the worst OS, HPV-positive/wild-type p53 with best OS, and HPV-positive/aberrant p53 or HPV-negative/wild-type p53 with intermediate OS. On multivariate analysis HPV status (p = 0.0063), patient age (p = 0.0054), T stage (p = 0.039), and lymph node involvement (p = 0.044) were independently associated with OS. PD-L1 expression (CPS ≥ 1) was seen in 30% of HPV-positive and 40% of HPV-negative cases, and PD-L1 positivity was associated with a trend toward inferior OS within the HPV-negative group (p = 0.064). Our findings suggest that anal SqCC can be subclassified into clinically, pathologically, and molecularly distinct groups based on HPV and TP53 mutation status, and p16 and p53 immunohistochemistry represent a clinically useful method of predicting these prognostic groups.

Immunohistochemistry features and molecular pathology of appendiceal neoplasms

Primary appendiceal neoplasms (ANs) comprise a heterogeneous group of tumors. The pathology and classification of ANs have been controversial, and thus, a new classification of these neoplasms was published in the World Health Organization (WHO) classification of tumors (5th edition, 2019). However, immunohistochemistry (IHC) features of epithelial ANs are not explained in this edition and the limited data on the molecular pathology of these tumors shows inconsistent findings in various studies. It would be useful to identify biomarkers appropriate for each subtype to better aid in treatment selection. Therefore, we reviewed the literature to investigate what is known of the molecular pathology and IHC features of the most frequently diagnosed pathological subtypes of epithelial ANs based on the recent classification. The inconsistencies in research findings regarding the IHC features and molecular pathology of ANs could be due to differences in the number of samples and their collection and preparation as well as to the lack of a universally accepted classification system for these neoplasms. However, the literature shows that epithelial ANs typically stain positive for MUC2, CK20, and CDX2 and that the expression of SATB2 protein could be used as a biomarker for appendix tumor origin. Low-grade appendiceal mucinous neoplasms tend to have mutations in KRAS and GNAS but are usually wild-type for BRAF, APC, and P53. Conversely, appendiceal adenocarcinomas are frequently found with mutations in KRAS, GNAS, P53, PIK3CA, and APC, and have significant nuclear expression of β-catenin, loss of nuclear or nuclear and cytoplasmic expression of SMAD4, and loss of cytoplasmic membranous expression of E-cadherin. Goblet cell carcinomas (GCCs) typically stain positive for keratin and mucin markers and are frequently mutated in P53 and chromatin-modifier genes, but they tend to be wild-type for KRAS, GNAS, APC, and PIK3CA. The expression of CK7 and SATB2 proteins is usually negative in appendiceal neuroendocrine neoplasms and they lack the mutations in common cancer-associated genes including APC, BRAF, SMAD4, and PIK3C. The available data suggest that GCCs have distinct molecular and immunohistochemical features and that they have characteristics more in common with adenocarcinoma than classical neuroendocrine tumors. In addition, MSI does not seem to have a role in the pathogenesis of epithelial ANs because they are rarely detected in these tumors. Finally, hereditary predisposition may have a role in the development of ANs because heterozygous CTNNβ1, NOTCH1, and NOTCH4 germline mutations have recently been identified in low and high grades ANs.

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.

Molecular and clinicopathological features of appendiceal mucinous neoplasms

Appendiceal mucinous tumors (AMTs) include low-grade mucinous appendiceal neoplasms (LAMNs), high-grade mucinous appendiceal neoplasms (HAMNs), and mucinous adenocarcinomas (MACs). We collected 51 AMT samples (LAMN: 34, HAMN: 8, MAC: 9). Three of the eight HAMN cases contained LAMN components, and four out of nine MAC cases contained LAMN and/or HAMN components within the tumor. A next-generation sequencing (NGS) cancer hotspot panel was used to analyze 11 pure LAMN, 4 HAMN, and 3 MAC cases. The results revealed KRAS and GNAS as the most frequently mutated genes. Sanger sequencing was then performed to detect KRAS, GNAS, and TP53 mutations in the remaining 31 cases and RNF43 mutations in all cases. KRAS/GNAS and TP53 mutations occurred exclusively in pure LAMNs; however, five LAMN cases had mutations in both KRAS and GNAS. RNF43 mutations almost exclusively occurred with KRAS/GNAS mutations in pure LAMNs. In MAC and HAMN, KRAS/GNAS mutation status was nearly preserved between lower-grade areas. Most of the detected RNF43 mutations was missense type. RNF43 mutations were detected in both components of MAC with lower-grade area; however, RNF43 mutations detected in these two lesions were entirely different. RNF43 mutations were detected in only one of the eight HAMN patients, which was the sole case without pseudomyxoma peritonei (PMP). None of the four MAC patients with RNF43 mutation showed PMP. These findings suggest that RNF43 mutations occur at a later stage of MAC development and do not associate with PMP. Furthermore, a gradual transition from LAMN to MAC via HAMN could be considered.