Immunophenotype analysis using CLDN18, CDH17, and PAX8 for the subcategorization of endocervical adenocarcinomas in situ: gastric-type, intestinal-type, gastrointestinal-type, and Müllerian-type

Cell lineage-specific immunohistochemical markers in biliary intraepithelial neoplasia: Implications for subclassification and grading

Biliary intraepithelial neoplasia (BilIN), a precursor to cholangiocarcinoma, is categorized into low- and high-grade based on histological characteristics. Although gastric, intestinal, and biliary phenotypes of BilIN have been identified, detailed analyses of their immunophenotypic profiles using cell lineage-specific markers remain limited. This study aimed to define the immunohistochemical profiles of BilIN lesions, subclassify them based on their immunophenotypes, and correlate these profiles with histological grades. We examined 77 BilIN lesions from extrahepatic bile ducts, including 30 low- and 47 high-grade lesions, using immunohistochemical staining for gastric (claudin-18, MUC5AC), intestinal (cadherin-17, glycoprotein A33), and biliary (carbohydrate sulfotransferase 4) markers, along with progression markers (S100P, IMP3). Expression levels were semiquantitatively scored and correlated with histopathological features. BilIN lesions were classified into four immunophenotypes: gastric (G-type), intestinal (I-type), gastrointestinal (GI-type), and biliary (B-type). Low-grade lesions comprised G- (33.3 %), GI- (40 %), I- (13.3 %), and B-types (13.3 %), while high-grade lesions included G- (40.4 %), GI- (29.8 %), I- (21.3 %), and B-types (8.5 %). In low-grade BilIN, G-type lesions corresponded to gastric mucous cells, I-type to intestinal epithelial cells, and B-type to bile duct epithelial cells, while most GI-type lesions exhibited mixed G- and I-type components. High-grade BilIN differentiation based solely on histological characteristics was challenging to delineate due to overlapping features among I-, GI-, and B-type cells. S100P and IMP3 expression levels were significantly elevated in high-grade lesions, particularly within the I+B-type BilIN group, with no notable differences in G- or GI-type BilIN. Immunophenotypic profiling with lineage-specific markers effectively subclassified BilIN, enhancing the understanding of its histogenesis and progression.

Claudin-18 and Mutation Surrogate Immunohistochemistry in Gastric-type Endocervical Lesions and their Differential Diagnoses

Gastric-type endocervical adenocarcinomas (GAS) are aggressive HPV-independent neoplasms with molecular alterations in TP53 , STK11 , CDKN2A , and SMAD4 . Claudin-18 (CLDN18) has emerged as a useful marker to distinguish GAS from HPV-associated neoplasia. Its role in separating GAS from benign proliferations and exuberant endocervical glands is unknown. We studied the utility of immunohistochemistry for CLDN18, progesterone receptor (PR), and mutation surrogate stains (P53, STK11/LKB1, MTAP, SMAD4/DPC4) in 46 GAS, 12 benign gastric-type endocervical lesions, 54 benign Mullerian endocervical populations, and 11 HPV-associated endocervical adenocarcinomas. PD-L1 and HER2 immunostains were evaluated in GAS. Gastric-type lesions were more often positive for CLDN18 (100% benign, 78% GAS, most often well to moderately differentiated) compared to benign Mullerian endocervical specimens (all negative) and HPV-associated neoplasia (18%, always focal). Conversely, PR was negative in all gastric-type lesions and positive in 92% of benign Mullerian endocervical populations. GAS revealed aberrant/mutant expression of P53 in 35%, STK11/LKB1 in 25%, MTAP in 23%, and SMAD4/DPC4 in 9% of cases. Abnormal staining in at least one of these 4 mutation surrogate markers was present in 63% of GAS. HER2 score of 3+ was seen in 25% of GAS, and PD-L1 was positive in 37% based on a combined positive score. CLDN18 is a sensitive and highly specific marker of gastric-type benign and malignant endocervical lesions. Once a gastric-type phenotype is confirmed, mutation surrogate immunostains can be used to support a diagnosis of GAS. PD-L1 and HER2 expression is seen in a subset of GAS offering therapeutic options for this aggressive tumor.

The Clinicopathological and Molecular Characteristics of Endocervical Gastric-Type Adenocarcinoma and the Use of Claudin18.2 as a Potential Therapeutic Target

Endocervical gastric-type adenocarcinoma (GAS) is an aggressive type of endocervical mucinous adenocarcinoma characterized as being unrelated to human papillomavirus (HPV) and resistant to chemo/radiotherapy. In this study, we investigated the histology, immunohistochemistry patterns, and molecular characteristics in a large cohort of GAS (n = 62). Histologically, the majority of GAS cases exhibited a distinct morphology resembling gastric glands, although 2 exceptional cases exhibited HPV-associated adenocarcinoma morphology while retaining the characteristic histology of GAS at the invasive front. By immunohistochemistry, Claudin18.2 emerged as a highly sensitive and specific marker for GAS. Additionally, the strong expression of Claudin18.2 in patients with GAS indicated the potential of anti-Claudin18.2 therapy in the treatment of GAS. Other immunohistochemistry markers, including Muc6, p16, p53, Pax8, ER, and PR, may provide additional diagnostic clues for GAS. Quantitative methylation analysis revealed that the overexpression of Claudin18.2 in GAS was governed by the hypomethylation of the CLDN18.2 promoter CpG islands. To further elucidate the pathogenic mechanisms of GAS and its relationship with gastric adenocarcinoma, we performed whole exome sequencing on 11 GAS and 9 gastric adenocarcinomas. TP53, CDKN2A, STK11, and TTN emerged as the most frequently mutated genes in GAS. Mutations in these genes primarily affected cell growth, cell cycle regulation, senescence, and apoptosis. Intriguingly, these top mutated genes in GAS were also commonly mutated in gastric and pancreaticobiliary adenocarcinomas. Regarding germline variants, we identified a probably pathogenic variant in SPINK1, a gene linked to hereditary pancreatic cancer syndrome, in one GAS sample. This finding suggests a potential pathogenic link between pancreatic cancers and GAS. Overall, GAS exhibits molecular characteristics that resemble those observed in gastric and pancreaticobiliary adenocarcinomas, thereby lending support to the aggressive nature of GAS compared with HPV-associated adenocarcinoma.

Biology and management of lobular endocervical glandular hyperplasia

AIM

Lobular endocervical glandular hyperplasia (LEGH) is a multicystic proliferative disorder of the uterine cervix. The aim of this review was to clarify the current understanding of this unique tumor.

METHOD

This article reviews the chronological progress of research regarding clinico-pathological and genetic aspects of LEGH and related cervical cystic diseases such as Nabothian cyst and adenocarcinoma of gastric type (GAS), using the literature and data from our institute. We also describe clinical management including preoperative diagnosis and adequate surgical/expectant treatment based on the biological features.

RESULTS

Recent studies revealed several unique aspects of LEGH, that is, (i) production of gastric mucin, (ii) symptomatic and histological similarity with minimal deviation adenocarcinoma (MDA), and (iii) frequent association with GAS, including MDA. These findings indicated that LEGH is a gastric metaplasia, as well as pre-cancerous neoplasia. For the preoperative diagnosis of LEGH, the combination of "cosmos" sign on magnetic resonance imaging, detection of gastric mucin, and lack of nuclear atypia on cytology is important. Cone biopsy is effective for pathological diagnosis. Simple hysterectomy is indicated as surgical treatment for LEGH; however, meticulous follow-up is also an option, especially for young patients, because the rate of malignant transformation was reported to be 1%-2%. For LEGH patients who selected follow-up, a worsening cytology and increase in lesion size were important signs of malignant change of LEGH for safe follow-up.

CONCLUSION

Proper understanding of the characteristics of LEGH is important for adequate management.

Membranous and nuclear staining of CLDN18 in HPV-independent and HPV-associated endocervical adenocarcinomas

OBJECTIVES

A classification system for endocervical adenocarcinoma (ECA) based on high-risk human papillomavirus (HPV) status has been established; however, the immunohistochemical markers distinguishing HPV-independent and HPV-associated ECAs have not been fully described. Here, we aimed to characterize ECA immunopathological features.

METHODS

We evaluated the immunohistochemical profile of CLDN18, CDX2, PAX8, p16, p53, and CEA in 60 ECAs comprising 10 HPV-independent ECAs and 50 HPV-associated ECAs. Both the membranous and nuclear expression levels of CLDN18 were analyzed.

RESULTS

Membranous CLDN18 (CLDN18 [M]) was found to be expressed in the mucinous epithelium of all HPV-independent ECAs, including eight gastric-type ECAs (G-ECAs), one endometrioid ECA, and one clear cell ECA, but no nuclear CLDN18 (CLDN18 [N]) expression was detected in HPV-independent ECAs. Among HPV-associated ECAs, CLDN18 (M) expression levels in intestinal-type (I-ECAs) and usual-type ECAs (U-ECAs) were significantly different from those in invasive stratified mucin-producing (iSMILE) carcinomas (p = 0.036). Positive CLDN18 (M) staining was present in 55.6% (5/9) of intestinal-type and 39.4% (13/33) of usual-type ECAs and was not present in iSMILE ECAs. Silva pattern C cancers expressed higher levels of CLDN18 (M) than Silva pattern A and B cancers (p = 0.004), whereas the CLDN18 (N) expression levels in cancers showing Silva pattern A were significantly higher than those in cancers exhibiting Silva patterns B and C (p < 0.001).

CONCLUSION

Membranous CLDN18 is expressed in ECAs and is particularly frequently expressed in HPV-independent ECAs, and membranous CLDN18 expression has potential as a therapeutic target. Nuclear staining of CLDN18 is a new immunohistochemical marker for diagnosing Silva pattern A HPV-associated ECAs and is associated with a good prognosis. Further studies should investigate the therapeutic and prognostic significance of membranous and nuclear CLDN18 expression and develop a related test that can be implemented in the clinical evaluation of ECAs.

Squamous and Glandular Epithelial Tumors of the Cervix: A Pragmatical Review Emphasizing Emerging Issues in Classification, Diagnosis, and Staging

Squamous cell carcinoma is the most frequent epithelial malignant tumor of the cervix and among the most frequent neoplasm in women worldwide. Endocervical adenocarcinoma is the second most common malignancy. Both tumors and their precursors are currently classified based on human papillomavirus status, with prognostic and predictive value. Various prognostic biomarkers and alternative morphologic parameters have been recently described and could be used in the management of these patients. This pragmatical review highlights recent developments, emerging issues as well as controversial areas regarding the cause-based classification, diagnosis, staging, and prognostic parameters of epithelial malignant tumors of the cervix.

Claudin-18 as a Promising Surrogate Marker for Endocervical Gastric-type Carcinoma

HIK1083 and trefoil factor 2 (TFF2) are known to be expressed in gastric-type carcinoma (GAS), but they do not reliably mark all GASs, and focal expression can be missed in biopsy specimens. We aimed to investigate whether claudin-18 and alpha-methylacyl-CoA racemase (AMACR) could be surrogate markers to separate GAS from other types of endocervical adenocarcinoma (ECA) and to compare their usefulness with that of HIK1083 and TFF2. Claudin-18 and AMACR immunohistochemistry was performed, and the results were compared with that of TFF2 and HIK1083, using whole sections of 75 ECAs (22 GASs and 53 non-GASs) and 179 ECAs with tissue microarrays (TMAs). TMAs were built to simulate the assessment of immunohistochemical stains in small biopsies. Any membranous (claudin-18) or cytoplasmic/membranous (AMACR, TFF2, HIK1083) staining of >5% of tumor cells was considered positive. Of 75 ECAs with whole sections, claudin-18 was significantly more frequently expressed in GASs (21/22) compared with non-GASs (8/53) (P<0.01). In ECAs with TMAs, claudin-18 expression was significantly frequent in GASs (15/23, 65.2%) than in non-GASs (3/152, 2.0%; all usual-type) (P<0.01). All claudin-18-positive GASs showed intense staining except 1 case. Claudin-18 shared the same degree of sensitivity and specificity with HIK1083 and TFF2. Three clear cell carcinomas were positive for claudin-18, but none showed intense staining. AMACR was expressed in a subset of ECAs and showed no impact in distinguishing between GAS and other ECAs. Our results suggest that claudin-18 is a promising surrogate marker to separate GAS from other types of ECA, including clear cell carcinoma.

Clinicopathological and prognostic significance of immunophenotypic characterization of endocervical adenocarcinoma using CLDN18, CDH17, and PAX8 in association with HPV status

In 2020, the WHO published a new system for classifying invasive endocervical adenocarcinoma based on histological features and high-risk human papillomavirus (HPV) infection. However, immunophenotypes of each histological subtype require further investigation. We immunohistochemically analyzed 66 invasive endocervical adenocarcinomas using three cell-lineage-specific markers: claudin 18 (CLDN18) for gastric, cadherin 17 (CDH17) for intestinal, and PAX8 for Müllerian epithelial cells. We identified five immunophenotypes of endocervical adenocarcinoma: gastric (21%); intestinal (14%); gastrointestinal (11%); Müllerian (35%); and not otherwise specified (NOS) (20%). Adenocarcinomas with gastric immunophenotype, characterized by aging (p = 0.0050), infrequent HPV infection (p < 0.0001), concurrent lobular endocervical glandular hyperplasia (p = 0.0060), lymphovascular invasion (p = 0.0073), advanced clinical stage (p = 0.0001), and the poorest progression-free (p < 0.0001) and overall (p = 0.0023) survivals, were morphologically compatible with gastric-type adenocarcinoma of the WHO 2020 classification. Conversely, most adenocarcinomas with Müllerian (91%) and intestinal (89%) immunophenotypes were HPV associated and morphologically compatible with usual- or intestinal-type adenocarcinomas of the WHO 2020 classification. The morphology of adenocarcinomas with gastrointestinal immunophenotype was intermediate or mixed between those of gastric and intestinal immunophenotypes; 57% were HPV associated. Adenocarcinomas with NOS immunophenotype were mainly HPV associated (85%) and histologically poorly differentiated. Multivariate analysis revealed that gastric (p = 0.008), intestinal + gastrointestinal (p = 0.0103), and NOS (p = 0.009) immunophenotypes were independent predictors of progression-free survival. Immunophenotypes characterized by CLDN18, CDH17, and PAX8 exhibited clinicopathological relevance and may improve the diagnostic accuracy and prognostic value of conventional histological classification.

Targeting claudins in cancer: diagnosis, prognosis and therapy

Increasing evidence has linked claudins to signal transduction and tumorigenesis. The expression of claudins is frequently dysregulated in the context of neoplastic transformation, suggesting their promise as biomarkers for diagnosis and prognosis or targets for treatment. Claudin binders (Clostridium perfringens enterotoxin and monoclonal antibody) have been tested in preclinical experiments, and some of them have progressed into clinical trials involving patients with certain cancers. However, the clinical development of many of these agents has not advanced to clinical applications. Herein, I review the current status of preclinical and clinical investigations of agents targeting claudins for diagnosis, prognosis and therapy. I also discuss the potential of combining claudin binders with other currently approved therapeutic agents.