Tumor and α-SMA-expressing stromal cells in pancreatic neuroendocrine tumors have a distinct RNA profile depending on tumor grade.

Alpha-smooth muscle actin (α-SMA) expression in the stroma is linked to the presence of cancer-associated fibroblasts and is known to correlate with worse outcomes in various tumors. In this study, using a GeoMx digital spatial profiling approach, we characterized the gene expression of the tumor and α-SMA-expressing stromal cell compartments in pancreatic neuroendocrine tumors (PanNETs). The profiling was performed on tissues from eight retrospective cases (three grade 1, four grade 2, and one grade 3). Selected regions of interest were segmented geometrically based on tissue morphology and fluorescent signals from synaptophysin and α-SMA markers. The α-SMA-expressing stromal-cell-associated genes were involved in pathways of extracellular matrix modification, whereas, in tumor cells, the gene expression profiles were associated with pathways involved in cell proliferation. The comparison of gene expression profiles across all three PanNET grades revealed that the differences between grades are not only present at the level of the tumor but also in the α-SMA-expressing stromal cells. Furthermore, the tumor cells from regions with a rich presence of adjacent α-SMA-expressing stromal cells revealed an upregulation of matrix metalloproteinase-9 (MMP9) expression in grade 3 tumors. This study provides an in-depth characterization of gene expression profiles in α-SMA-expressing stromal and tumor cells, and outlines potential crosstalk mechanisms.

Transcriptomic Differences in Medullary Thyroid Carcinoma According to Grade.

Medullary thyroid carcinoma (MTC) is a rare cancer derived from neuroendocrine C-cells of the thyroid. In contrast to other neuroendocrine tumors, a histological grading system was lacking until recently. A novel two-tier grading system based on the presence of high proliferation or necrosis is associated with prognosis. Transcriptomic analysis was conducted on 21 MTCs, including 9 high-grade tumors, with known mutational status, using the NanoString Tumor Signaling 360 Panel. This analysis, covering 760 genes, revealed upregulation of the genes EGLN3, EXO1, UBE2T, UBE2C, FOXM1, CENPA, DLL3, CCNA2, SOX2, KIF23, and CDCA5 in high-grade MTCs. Major pathways differentially expressed between high-grade and low-grade MTCs were DNA damage repair, p53 signaling, cell cycle, apoptosis, and Myc signaling. Validation through qRT-PCR in 30 MTCs demonstrated upregulation of ASCL1, DLL3, and SOX2 in high-grade MTCs, a gene signature akin to small-cell lung carcinoma, molecular subgroup A. Subsequently, DLL3 expression was validated by immunohistochemistry. MTCs with DLL3 overexpression (defined as ≥ 50% of positive tumor cells) were associated with significantly lower disease-free survival (p = 0.041) and overall survival (p = 0.01). Moreover, MTCs with desmoplasia had a significantly increased expression of DLL3. Our data supports the idea that DLL3 should be further explored as a predictor of aggressive disease and poor outcomes in MTC.

Performance of the Idylla microsatellite instability test in endometrial cancer.

CONTEXT: DNA mismatch repair (MMR) deficiency (dMMR) testing is now recommended in endometrial cancer. Defect identification in the molecules participating in this pathway, or the presence of microsatellite instability, are commonly employed for this purpose. Novel methods are continuously evolving to report dMMR/microsatellite instability and to easily perform routine diagnoses. OBJECTIVE: The main aim of this study was to compare the concordance of the Idylla microsatellite instability test for the identification of dMMR endometrial cancer samples defined by immunohistochemistry and MMR genomic status. DESIGN: We applied the Idylla MSI test to 126 early-stage endometrial cancer cases with MMR testing by immunohistochemistry and genomic characterization (methylation in MLH1 and sequence alterations in MLH1, PMS2, MSH2 and MSH6). Individual markers and overall specific performance indicators were explored. RESULTS: The Idylla platform achieved a higher global concordance rate with MMR genomic status than with immunohistochemistry (75 % and 66 %, respectively). Sensitivity and specificity are also higher (75 % vs 66 % and 96 % vs 90 %, respectively). Clustering analysis split the patients into 2 well-differentiated clusters, the pMMR and the dMMR group, represented by MLH1/PMS2 loss and the MLH1 methylated promoter. Overall, immunohistochemistry and MMR genomic status identified more dMMR cases than did the Idylla test, although correlations were improved with a modified Idylla test cut-off. CONCLUSIONS: Performance of the Idylla test was better correlated with MMR genomic status than MMR immunohistochemistry status, which improved with a modified test cut-off. Further studies are needed to confirm the cut-off accuracy.

Enteroblastic adenocarcinoma of the ampulla of Vater / Adenocarcinoma enteroblástico de la ampolla de Vater

Adenocarcinoma with enteroblastic differentiation is a rare histologic subtype of adenocarcinoma of the gastrointestinal tract that shows unique histologic and immunohistochemical features that resemble fetal intestinal epithelium. This histological subtype has been widely described in the stomach, where it most frequently appears, but, in other locations, it is misdiagnosed because of the poor experience in routine diagnostic setting. Here we present a case of an 87-year-old male with an adenocarcinoma of the ampulla of Vater with enteroblastic differentiation with a literature review of the cases described of this subtype in this location to date. The anatomical peculiarity of the ampulla, joined with the infrequent nature of this histological subtype, makes this case of great interest to aid to better characterize the biological behavior of these tumors. (AU)

El adenocarcinoma con diferenciación enteroblástica es un subtipo histológico poco frecuente de adenocarcinoma gastrointestinal que muestra características histológicas e inmunohistoquímicas únicas que se asemejan al epitelio intestinal fetal. Este subtipo histológico ha sido ampliamente descrito en el estómago, donde aparece con mayor frecuencia, pero en otras localizaciones es mal diagnosticado debido a la poca experiencia en el diagnóstico de rutina. Presentamos un caso de un varón de 87 años con adenocarcinoma de ampolla de Vater con diferenciación enteroblástica, junto a una revisión bibliográfica de los casos descritos de este subtipo en esta localización hasta el momento. La peculiaridad anatómica de la ampolla, sumada al carácter poco frecuente de este subtipo histológico, dotan a este caso de gran interés para ayudar a caracterizar mejor el comportamiento biológico de estos tumores. (AU)

Pegvisomant and pasireotide in PRL and GH co-secreting vs GH-secreting Pit-NETs.

The objective of the study was to evaluate the efficacy of second-line therapies in patients with acromegaly caused by a growth hormone (GH) and prolactin (PRL) co-secreting pituitary neuroendocrine tumor (GH&PRL-Pit-NET) compared to their efficacy in patients with acromegaly caused by a GH-secreting pituitary neuroendocrine tumor (GH-Pit-NET). This is a multicenter retrospective study of patients with acromegaly on treatment with pasireotide and/or pegvisomant. Patients were classified in two groups: GH&PRL-Pit-NETs when evidence of hyperprolactinemia and immunohistochemistry (IHC) for GH and PRL was positive or if PRL were >200 ng/dL regardless of the PRL-IHC and GH-Pit-NETs when the previously mentioned criteria were not met. A total of 28 cases with GH&PRL-Pit-NETs and 122 with GH-Pit-NETs met the inclusion criteria. GH&PRL-Pit-NETs presented at a younger age, caused hypopituitarism, and were invasive more frequently than GH-Pit-NETs. There were 124 patients treated with pegvisomant and 49 with pasireotide at any time. The efficacy of pegvisomant for IGF-1 normalization was of 81.5% and of pasireotide of 71.4%. No differences in IGF-1 control with pasireotide and with pegvisomant were observed between GH&PRL-Pit-NETs and GH-Pit-NETs. All GH&PRL-Pit-NET cases treated with pasireotide (n = 6) and 82.6% (n = 19/23) of the cases treated with pegvisomant normalized PRL levels. No differences in the rate of IGF-1 control between pegvisomant and pasireotide were detected in patients with GH&PRL-Pit-NETs (84.9% vs 66.7%, P = 0.178). We conclude that despite the more aggressive behavior of GH&PRL-Pit-NETs than GH-Pit-NETs, no differences in the rate of IGF-1 control with pegvisomant and pasireotide were observed between both groups, and both drugs have shown to be effective treatments to control IGF-1 and PRL hypersecretion in these tumors.

The best linear unbiased prediction (BLUP) method as a tool to estimate the lifetime risk of pancreatic ductal adenocarcinoma in high-risk individuals with no known pathogenic germline variants.

Pancreatic ductal adenocarcinoma (PDAC) is the fourth leading cause of cancer-related death in the Western world. The number of diagnosed cases and the mortality rate are almost equal as the majority of patients present with advanced disease at diagnosis. Between 4 and 10% of pancreatic cancer cases have an apparent hereditary background, known as hereditary pancreatic cancer (HPC) and familial pancreatic cancer (FPC), when the genetic basis is unknown. Surveillance of high-risk individuals (HRI) from these families by imaging aims to detect PDAC at an early stage to improve prognosis. However, the genetic basis is unknown in the majority of HRIs, with only around 10-13% of families carrying known pathogenic germline mutations. The aim of this study was to assess an individual's genetic cancer risk based on sex and personal and family history of cancer. The Best Linear Unbiased Prediction (BLUP) methodology was used to estimate an individual's predicted risk of developing cancer during their lifetime. The model uses different demographic factors in order to estimate heritability. A reliable estimation of heritability for pancreatic cancer of 0.27 on the liability scale, and 0.07 at the observed data scale as obtained, which is different from zero, indicating a polygenic inheritance pattern of PDAC. BLUP was able to correctly discriminate PDAC cases from healthy individuals and those with other cancer types. Thus, providing an additional tool to assess PDAC risk HRI with an assumed genetic predisposition in the absence of known pathogenic germline mutations.

Effectiveness of combined first-line medical treatment in acromegaly with prolactin cosecretion.

OBJECTIVE: The aim of this study is to compare the response to first-line medical treatment in treatment-naive acromegaly patients with pure growth hormone (GH)-secreting pituitary adenoma (GH-PA) and those with GH and prolactin cosecreting PA (GH&PRL-PA). DESIGN: This is a retrospective multicentric study of acromegaly patients followed from 2003 to 2023 in 33 tertiary Spanish hospitals with at least 6 months of first-line medical treatment. METHODS: Baseline characteristics, first-line medical treatment strategies, and outcomes were analyzed. We employed a multiple logistic regression full model to estimate the impact of some baseline characteristics on disease control after each treatment modality. RESULTS: Of the 144 patients included, 72.9% had a GH-PA, and 27.1% had a GH&PRL-PA. Patients with GH&PRL-PA were younger (43.9 ± 15.0 vs 51.9 ± 12.7 years, P < .01) and harboring more frequently macroadenomas (89.7% vs 72.1%, P = .03). First-generation somatostatin receptor ligand (fgSRL) as monotherapy was given to 106 (73.6%) and a combination treatment with fgSRL and cabergoline in the remaining 38 (26.4%). Patients with GH&PRL-PA received more frequently a combination therapy (56.4% vs 15.2%, P < .01). After 6 months of treatment, in the group of patients under fgSRL as monotherapy, those patients with GH&PRL-PA had worse control compared to GH-PAs (29.4% vs 55.1%, P = .04). However, these differences in the rate of disease control between both groups disappeared when both received combination treatment with fgSRL and cabergoline. CONCLUSION: In GH&PRL-PA, the biochemical control achieved with fgSRL as monotherapy is substantially worse than in patients harboring GH-PA, supporting the inclusion of cabergoline as first-line medical treatment in combination with fgSRLs in these subgroups of patients.

The Peptidoglycan Recognition Protein 1 confers immune evasive properties on pancreatic cancer stem cells.

OBJECTIVE: Pancreatic ductal adenocarcinoma (PDAC) has limited therapeutic options, particularly with immune checkpoint inhibitors. Highly chemoresistant 'stem-like' cells, known as cancer stem cells (CSCs), are implicated in PDAC aggressiveness. Thus, comprehending how this subset of cells evades the immune system is crucial for advancing novel therapies. DESIGN: We used the KPC mouse model (LSL-KrasG12D/+; LSL-Trp53R172H/+; Pdx-1-Cre) and primary tumour cell lines to investigate putative CSC populations. Transcriptomic analyses were conducted to pinpoint new genes involved in immune evasion. Overexpressing and knockout cell lines were established with lentiviral vectors. Subsequent in vitro coculture assays, in vivo mouse and zebrafish tumorigenesis studies, and in silico database approaches were performed. RESULTS: Using the KPC mouse model, we functionally confirmed a population of cells marked by EpCAM, Sca-1 and CD133 as authentic CSCs and investigated their transcriptional profile. Immune evasion signatures/genes, notably the gene peptidoglycan recognition protein 1 (PGLYRP1), were significantly overexpressed in these CSCs. Modulating PGLYRP1 impacted CSC immune evasion, affecting their resistance to macrophage-mediated and T-cell-mediated killing and their tumourigenesis in immunocompetent mice. Mechanistically, tumour necrosis factor alpha (TNFα)-regulated PGLYRP1 expression interferes with the immune tumour microenvironment (TME) landscape, promoting myeloid cell-derived immunosuppression and activated T-cell death. Importantly, these findings were not only replicated in human models, but clinically, secreted PGLYRP1 levels were significantly elevated in patients with PDAC. CONCLUSIONS: This study establishes PGLYRP1 as a novel CSC-associated marker crucial for immune evasion, particularly against macrophage phagocytosis and T-cell killing, presenting it as a promising target for PDAC immunotherapy.

The Spanish Familial Pancreatic Cancer Registry (PANGENFAM): a decade follow-up of individuals at high-risk for pancreatic cancer.

The Spanish Familial Pancreatic Cancer Registry (PANGENFAM) was established in 2009 and aims to characterize the genotype and phenotype of familial pancreatic cancer (FPC). Furthermore, an early detection screening program for pancreatic ductal adenocarcinoma (PDAC) is provided to healthy high-risk individuals from FPC and hereditary pancreatic cancer families (first-degree relatives). This article describes our experience over the last 10 years in high-risk screening. Hereditary and familial pancreatic cancer families were identified through the oncology and gastroenterology units. High-risk individuals underwent annual screening with endoscopic ultrasound (EUS) and magnetic resonance (MRI) from age 40 or 10 years younger than the youngest affected family member. Results: PANGENFAM has enrolled 290 individuals from 143 families, including 52 PDAC cases and 238 high-risk individuals. All high-risk individuals eligible for screening were offered to enter the surveillance program, with 143 currently participating. Pancreatic abnormalities were detected in 94 individuals (median age 53 years (29-83), with common findings including cystic lesions and inhomogeneous parenchyma. Imaging test concordance was 66%. Surgical intervention was performed in 4 high-risk individuals following highly suspicious lesions detected by imaging. PANGENFAM is a valuable resource for science innovation, such as biobanking, with clinical and imaging data available for analysis. For high-risk families, it may offer a potential for early diagnosis. Collaboration with other national and international registries is needed to increase our understanding of the disease biology and to standardize criteria for inclusion and follow-up, optimizing cost-effectiveness and efficacy.

Enteroblastic adenocarcinoma of the ampulla of Vater.

Adenocarcinoma with enteroblastic differentiation is a rare histologic subtype of adenocarcinoma of the gastrointestinal tract that shows unique histologic and immunohistochemical features that resemble fetal intestinal epithelium. This histological subtype has been widely described in the stomach, where it most frequently appears, but, in other locations, it is misdiagnosed because of the poor experience in routine diagnostic setting. Here we present a case of an 87-year-old male with an adenocarcinoma of the ampulla of Vater with enteroblastic differentiation with a literature review of the cases described of this subtype in this location to date. The anatomical peculiarity of the ampulla, joined with the infrequent nature of this histological subtype, makes this case of great interest to aid to better characterize the biological behavior of these tumors.

Differences between GH and PRL co-secreting and GH-secreting pituitary adenomas. A series of 604 cases.

PURPOSE: To evaluate differences in clinical presentation and in surgical outcomes between growth hormone-secreting pituitary adenomas (GH-PAs) and GH and prolactin co-secreting pituitary adenomas (GH&PRL-PAs). METHODS: Multicenter retrospective study of 604 patients with acromegaly submitted to pituitary surgery. Patients were classified into two groups according to serum PRL levels at diagnosis and immunohistochemistry (IHC) for PRL: a) GH&PRL-PAs when PRL levels were above the upper limit of normal and IHC for GH and PRL was positive or PRL levels were >100ng/and PRL IHC was not available (n=130) and b) GH-PAs who did not meet the previously mentioned criteria (n=474). RESULTS: GH&PRL-PAs represented 21.5% (n=130) of patients with acromegaly. The mean age at diagnosis was lower in GH&PRL-PAs than in GH-PAs (P<0.001). GH&PRL-PAs were more frequently macroadenomas (90.6% vs. 77.4%, P=0.001) and tended to be more invasive (33.6% vs. 24.7%, P=0.057) than GH-PAs. Furthermore, they had presurgical hypopituitarism more frequently (OR 2.8, 95% CI 1.83-4.38). IGF-1 upper limit of normality (ULN) levels at diagnosis were lower in patients with GH&PRL-PAs (median 2.4 [IQR 1.73-3.29] vs. 2.7 [IQR 1.91-3.67], P=0.023). There were no differences in the immediate (41.1% vs 43.3%, P=0.659) or long-term post-surgical acromegaly biochemical cure rate (53.5% vs. 53.1%, P=0.936) between groups. However, there was a higher incidence of permanent arginine-vasopressin deficiency (AVP-D) (7.3% vs. 2.4%, P=0.011) in GH&PRL-PAs patients. CONCLUSIONS: GH&PRL-PAs are responsible for 20% of acromegaly cases. These tumors are more invasive, larger and cause hypopituitarism more frequently than GH-PAs and are diagnosed at an earlier age. The biochemical cure rate is similar between both groups, but patients with GH&PRL-PAs tend to develop permanent postsurgical AVP-D more frequently.

Primary Cilia as a Tumor Marker in Pituitary Neuroendocrine Tumors.

Pituitary neuroendocrine tumors (PitNETs) account for approximately 15% of all intracranial neoplasms. Although they usually appear to be benign, some tumors display worse behavior, displaying rapid growth, invasion, refractoriness to treatment, and recurrence. Increasing evidence supports the role of primary cilia (PC) in regulating cancer development. Here, we showed that PC are significantly increased in PitNETs and are associated with increased tumor invasion and recurrence. Serial electron micrographs of PITNETs demonstrated different ciliation phenotypes (dot-like versus normal-like cilia) that represented PC at different stages of ciliogenesis. Molecular findings demonstrated that 123 ciliary-associated genes (eg, doublecortin domain containing protein 2, Sintaxin-3, and centriolar coiled-coil protein 110) were dysregulated in PitNETs, representing the upregulation of markers at different stages of intracellular ciliogenesis. Our results demonstrate, for the first time, that ciliogenesis is increased in PitNETs, suggesting that this process might be used as a potential target for therapy in the future.

Surgery for adrenal metastasis: Surgical outcomes and prognostic factors for long-term survival.

PURPOSE: To analyze surgical outcomes and predictive factors for long-term overall and disease-specific survival in patients undergoing surgical resection of adrenal metastasis. METHODS: A multicenter retrospective study included patients who underwent adrenalectomy for adrenal metastasis in two Spanish hospitals between 2005 and 2021. Clinical variables associated with surgical complications and survival during follow-up were analyzed. RESULTS: Thirty-three patients were included. Adrenalectomy was performed laparoscopically in 27 patients and by an open approach in 6. The most common primary tumor site was the lung (n=15), followed by the kidney (n=7). Most patients had metachronous lesions (n=28). Six patients (18.2%) had intra- and/or postoperative complications; synchronous metastasis was a risk factor (odds ratio 12.5 [1.45-107.6]) for their development. Progression-free survival and disease-specific survival were 7.5months (range 1-64) and 22.5months (6-120), respectively. Survival rates at 1, 2, 3 and 5years were 94%, 65%, 48% and 29%, respectively. Survival was significantly lower in patients with lung cancer than with other cancers (hazard ratio 4.23 [1.42-12.59]). CONCLUSIONS: Adrenalectomy for solitary adrenal metastases was associated with intra- or postoperative complications in 18% of cases. Synchronous metastasis was a risk factor for complications.

Case report: Efficacy of immunotherapy as conversion therapy in dMMR/MSI-H colorectal cancer: a case series and review of the literature.

Immunotherapy has demonstrated a role in the therapeutic landscape of a small subset of patients with colorectal carcinoma (CRC) that harbor a microsatellite instability (MSI-H) status due to a deficient DNA mismatch repair (dMMR) system. The remarkable responses to immune checkpoint inhibitors (ICIs) are now being tested in the neoadjuvant setting in localized CRC, where the dMMR/MSI-H status can be found in up to 15% of patients, with remarkable results obtained in NICHE2 and 3 trials, among others. This case series aims to report our experience at a tertiary center and provide a comprehensive analysis of the possible questions and challenges to overcome if ICIs were established as standard of care in a neoadjuvant setting, as well as the potential role they may have as conversion therapy not only in locoregional advanced CRC but also in oligometastatic disease.

Lymphoglandular Complex-Like Colorectal Carcinoma-A Series of 20 Colorectal Cases, Including Newly Reported Features of Malignant Behavior.

Distinguishing colon carcinoma that is surrounded by well-circumscribed lymphoid tissue from adenomas involving lymphoglandular complexes can be difficult. We assessed a multi-institutional international cohort of 20 colorectal carcinomas with associated prominent lymphoid infiltrates, which we referred to as lymphoglandular complex-like carcinoma (LGCC). We collected clinical and endoscopic features, including lesion size, endoscopic appearance, location, procedure, follow-up, AJCC stage, and mismatch repair status. We recorded the presence of the following histologic features: haphazard gland distribution, gland angulation, gland fusion, solid nest formation, single-cell formation, stromal desmoplasia, presence of lymphovascular invasion and perineural invasion, presence of lamina propria, cytologic atypia as low- or high-grade, presence of goblet cells in the invasive component, and the presence of a surface lesion. Most cases (9 of 13) were described endoscopically as sessile polyps with an average size of 1.56 cm. Most cases (90%) were associated with a surface lesion, of which the majority were tubular adenomas, though a subset was associated with sessile serrated lesions with dysplasia (3 of 18). All cases of LGCC demonstrated haphazard gland distribution and either gland angulation, fusion, or solid nest formation. A portion of cases demonstrated single-cell infiltration (35%) and desmoplasia (50%), and rarely lymphovascular invasion was present (5%). A subset (10%) of cases invaded beyond the submucosa. Deficient mismatch repair was present in 22% (2 of 9) of cases for which it was performed. In cases of colectomy or completion colectomy, nodal metastasis was present in 38% (3 of 8). No cases demonstrated disease recurrence or disease-specific mortality. Overall, LGCC represents an enigmatic subset of carcinomas that is important to distinguish from adenomas involving lymphoglandular complexes due to its varying prognostic outcomes.

Influence of obesity and overweight in surgical outcomes of adrenalectomy for primary adrenal disease: A cohort study of 146 cases.

OBJECTIVE: To evaluate the impact of obesity and overweight on surgical outcomes in a large cohort of patients who underwent adrenalectomy due to benign or malignant primary adrenal disease. METHODS: A retrospective single-center study of patients without history of active extraadrenal malignancy, with adrenal tumors operated on consecutively in our center between January 2010 and December 2022. Obesity was defined as a body mass index (BMI)≥30kg/m2 and overweight as BMI between 25.0 and 30.0kg/m2. RESULTS: Of 146 patients with adrenal tumors who underwent adrenalectomy, 9.6% (n=14) were obese, 54.8% (n=80) overweight and 35.6% (n=52) normal weight. Obese patients had higher diastolic blood pressure (87.6±12.22 vs. 79.3±10.23mmHg, P=0.010) and a higher prevalence of dyslipidemia (57.1% vs. 25.8%, P=0.014) and bilateral tumors (14.3% vs. 3.1%, P=0.044) than non-obese patients. The rates of intraoperative and of postsurgical complications were similar between obese/overweight patients and patients with normal weight. However, a significantly higher rate of postsurgical complications (27.3% vs. 5.7%, P=0.009) and a longer hospital stay (5.4±1.39 vs. 3.5±1.78 days, P=0.007) were observed in patients with obesity than in non-obese patients. In the multivariant analysis, obesity, age, ASA>2 and tumor size were independent risk factors for postoperative complications, with obesity being the most important factor (OR 23.34 [2.23-244.24]). CONCLUSION: Obesity and overweight are common conditions in patients who undergo adrenalectomy. Adrenalectomy is considered a safe procedure in patients with overweight, but it is associated with a higher risk of postsurgical complications and longer hospital stay in obese patients.

Comparison of Methods for Testing Mismatch Repair Status in Endometrial Cancer.

Approximately 20-30% of endometrial carcinomas (EC) are characterized by mismatch repair (MMR) deficiency (dMMR) or microsatellite instability (MSI), and their testing has become part of the routine diagnosis. The aim of this study was to establish and compare the MMR status using various approaches. Immunohistochemistry (IHC), PCR-based MSI, and the detection of defects in the four key MMR genes (MLH1, PMS2, MSH2, and MSH6) via methylation-specific multiplex ligation-dependent probe amplification (MLPA) and targeted next-generation sequencing (NGS) were performed. MSH3 expression was also evaluated. A set of 126 early-stage EC samples were analyzed, 53.2% of which were dMMR and 46.8% of which were proficient MMR (pMMR) as determined using IHC, whereas 69.3% were classified as microsatellite stable, while 8.8% and 21.9% were classified MSI-low (MSI-L) and MSI-high (MSI-H), respectively. In total, 44.3% of the samples showed genetic or epigenetic alterations in one or more genes; MLH1 promoter methylation was the most common event. Although acceptable concordance was observed, there were overall discrepancies between the three testing approaches, mainly associated with the dMMR group. IHC had a better correlation with MMR genomic status than the MSI status determined using PCR. Further studies are needed to establish solid conclusions regarding the best MMR assessment technique for EC.

Spatial distribution of CD3- and CD8-positive lymphocytes as pretest for POLE wild-type in molecular subgroups of endometrial carcinoma.

Introduction: Over the years, the molecular classification of endometrial carcinoma has evolved significantly. Both POLEmut and MMRdef cases share tumor biological similarities like high tumor mutational burden and induce strong lymphatic reactions. While therefore use case scenarios for pretesting with tumor-infiltrating lymphocytes to replace molecular analysis did not show promising results, such testing may be warranted in cases where an inverse prediction, such as that of POLEwt, is being considered. For that reason we used a spatial digital pathology method to quantitatively examine CD3+ and CD8+ immune infiltrates in comparison to conventional histopathological parameters, prognostics and as potential pretest before molecular analysis. Methods: We applied a four-color multiplex immunofluorescence assay for pan-cytokeratin, CD3, CD8, and DAPI on 252 endometrial carcinomas as testing and compared it to further 213 cases as validation cohort from a similar multiplexing assay. We quantitatively assessed immune infiltrates in microscopic distances within the carcinoma, in a close distance of 50 microns, and in more distant areas. Results: Regarding prognostics, high CD3+ and CD8+ densities in intra-tumoral and close subregions pointed toward a favorable outcome. However, TCGA subtyping outperforms prognostication of CD3 and CD8 based parameters. Different CD3+ and CD8+ densities were significantly associated with the TCGA subgroups, but not consistently for histopathological parameter. In the testing cohort, intra-tumoral densities of less than 50 intra-tumoral CD8+ cells/mm2 were the most suitable parameter to assume a POLEwt, irrespective of an MMRdef, NSMP or p53abn background. An application to the validation cohort corroborates these findings with an overall sensitivity of 95.5%. Discussion: Molecular confirmation of POLEmut cases remains the gold standard. Even if CD3+ and CD8+ cell densities appeared less prognostic than TCGA, low intra-tumoral CD8+ values predict a POLE wild-type at substantial percentage rates, but not vice versa. This inverse correlation might be useful to increase pretest probabilities in consecutive POLE testing. Molecular subtyping is currently not conducted in one-third of cases deemed low-risk based on conventional clinical and histopathological parameters. However, this percentage could potentially be increased to two-thirds by excluding sequencing of predicted POLE wild-type cases, which could be determined through precise quantification of intra-tumoral CD8+ cells.