Modern Pathology最新文献

There is currently no standardized sentinel lymph node (SLN) immunohistochemistry (IHC) protocol for detecting Merkel cell carcinoma (MCC) metastases. A cost-effective, high-sensitivity panel could improve diagnostic accuracy and resource utilization. We evaluated 226 SLNs from 81 MCC patients using a panel of POU4F3, keratin 20, and keratin AE1/AE3 or pan-keratin. Metastasis was defined as positive staining for any of the tested IHC markers. Patients ranged from 49-92 years (median, 73.5 years), with a male: female ratio of 1.8:1. Primary tumor sites were extremities (48.1%), head/neck (34.6%), and trunk (17.3%). SLN locations included cervical (29.6%), axillary (27%), femoral (20.8%), inguinal (9.7%), facial (7.1%), pelvic (3.1%), and epitrochlear (2.7%). Metastases were identified in 102/226 (45%) SLNs. Single marker sensitivities were: POU4F3 (96%, 98/102), keratin 20 (67%, 68/102), and keratin AE1/AE3 or pan-keratin (64%, 70/102). The most sensitive combinations were POU4F3 with keratin AE1/AE3 or pan-keratin (100% sensitivity) or POU4F3 with keratin 20 (98% sensitivity). Keratin 20 with keratin AE1/AE3 or pan-keratin was least sensitive (74%). In 6 (7.4%) patients POU4F3 detected single metastatic cells in SLNs that were previously diagnosed at time of clinical diagnosis as negative by keratin 20 and keratin AE1/AE3 or pan-keratin panel. POU4F3 is the most sensitive individual IHC marker for detecting MCC SLN metastases. The optimal cost-effective panel is POU4F3 with keratin AE1/AE3 or pan-keratin, which achieves 100% sensitivity while reducing reliance on less effective stains. Adoption of this focused IHC panel may serve to standardize SLN evaluation for MCC and improve diagnostic accuracy and efficiency.

Regional lymph node metastasis is one of the main factors affecting cancer staging. However, the clinical and immunological implications of non-metastatic regional lymph nodes (nrLNs) remain poorly understood. Here, we investigated the prognostic significance of the morphological features of nrLNs in colorectal cancer (CRC) with microsatellite instability-high (MSI-H). Artificial intelligence-aided digital pathology-based quantification of 37 histological parameters in 873 whole-slide images comprising 5,785 nrLNs was performed in two independent cohorts of curatively resected MSI-H CRCs (discovery, n=103; validation, n=90). The prognostic value of each histological parameter was evaluated by univariate and multivariate disease-free survival analyses. Quantitative immunohistochemical analysis of tumor-infiltrating immune cells and whole-exome and transcriptome sequencing using tumor tissues were performed to assess associations between prognostic nrLN histological features and various tumor immuno-molecular factors. As a result, germinal center (GC)-related histological parameters, including the maximum area, mean area, sum area, and maximum diameter of GCs in the nrLNs, were identified as independent prognostic factors in both cohorts. The prognostic GC-related factors of nrLNs were significantly associated with tertiary lymphoid structures and B cell pathways activation but were not or inversely correlated with the densities of tumor-infiltrating T cells and macrophages. No significant associations were found between prognostic nrLN GC features and major tumor molecular factors such as tumor mutational burden, driver mutations, consensus molecular subtype, or CpG island methylator phenotype. In conclusion, quantitative GC-related histology of nrLNs can serve as a prognostic indicator for MSI-H CRC. Our findings suggest that GC-activated nrLNs may represent B cell-mediated antitumor immunity, independent of tumor-infiltrating T cells and tumor-intrinsic molecular characteristics.

USP8 is one of the members of ubiquitin-specific proteases deconjugating ubiquitin from target proteins. Beside USP6, it can be involved in tumorigenesis of mesenchymal neoplasms by binding to an activating fusion partner. Until now, USP8 fusion genes have been reported in calcified chondroid mesenchymal neoplasms, an inflammatory myofibroblastic tumor, a cardiac neoplasm and a retroperitoneal sarcoma. Herein, we describe the clinicopathologic and genetic/epigenetic features of seven USP8-associated tumors. The cohort included five male patients aged between 2 and 11 years, and two female patients aged 38 and 52 years. Lesions arose in the tongue, finger, hallux, arm, thoracic wall, right ventricle and leg. Five neoplasms were resected. One was a recent case; the others were without evidence of disease after 0.5-3 years. Two lesions were only biopsied, one was a recent case and the other had no signs of progression after 4 years. Histology showed nodular or infiltrative lesions comprising of bland looking myofibroblastic spindle cells arranged in mainly short fascicles. The cellularity was variable, and the background was myxoid and/or collagenous. An inflammatory reaction was variably seen. One lesion, however, had features of a chondroid calcified mesenchymal neoplasm. Using RNA sequencing, the following fusion partners of USP8 were found: SH3KBP1, RASA1, PDGFRA, CRK, PTPN11 and FARP1. By RNA-expression analysis, the two cases analyzed had a profile of nodular fasciitis; while using the Heidelberg sarcoma classifier, all cases had a similar methylation profile apart from other soft tissue tumor entities, suggesting that they form a separate group but are closely related to USP6 associated lesions. In conclusion, we broaden the spectrum of USP8 associated mesenchymal lesions in superficial, deep soft tissues and viscera (heart). Almost all lesions in this series display a myofibroblastic phenotype and harbor variable USP8 fusion partners. RNA-expression profiling indicates partial clustering with nodular fasciitis, suggesting some biological similarity. However, DNA methylation analysis consistently shows that these tumors form a distinct epigenetic group, separate from both nodular fasciitis and inflammatory myofibroblastic tumors. Taken together, these findings support the concept of a USP8-rearranged myofibroblastic neoplasm as a potentially distinct entity, but the precise relationship with nodular fasciitis and inflammatory myofibroblastic tumor remains uncertain. Further studies integrating morphology, epigenetics, and transcriptomics are needed to clarify this relationship.

Epstein-Barr virus-positive (EBV+) diffuse large B-cell lymphoma (DLBCL) and EBV+ classic Hodgkin lymphoma (CHL) are major B-cell lymphomas with EBV infection in elderly patients. Although they are regarded as distinct clinicopathologic entities, distinguishing EBV+ CHL from EBV+ DLBCL is often challenging because of their overlapping histological and immunophenotypic features. We characterized the spectrum of EBV+ large B-cell lymphoma in 57 patients aged ≥50 years, including 35 EBV+ DLBCL (12 polymorphic DLBCL [pDLBCL] and 23 monomorphic DLBCL [mDLBCL]) and 22 EBV+ CHL. Gene expression profiling revealed interferon-γ (IFNγ)-enrichment with overexpression of indoleamine 2,3-dioxygenase 1 (IDO1), an immunosuppressive enzyme, in more than half of pDLBCL (5/8), but less in mDLBCL (3/19) and CHL (1/19). Fluorescence in situ hybridization showed a higher frequency of 9p24.1-altered cells in CHL (54%; interquartile range [IQR], 42%-89%), but lower in pDLBCL (18%; IQR, 12%-23%) and mDLBCL (5%; IQR, 0%-30%). Notably, immunohistochemical expression of PDL1 was higher in pDLBCL than in mDLBCL, suggesting IFNγ-mediated upregulation. DLBCL with EBV latency type III (n = 13) exhibited lower tumor PDL1 expression and reduced IDO1-enriched microenvironment. Multivariate analysis of the total cohort revealed that both EBV latency type III and Eastern Cooperative Oncology Group performance status ≥2 were independently associated with shorter overall survival. EBV+ large B-cell lymphoma spectrum was reclassified into four molecular groups: (1) EBV latency type III suggestive of immune senescence (n = 10, 22%), (2) high proportion of 9p24.1-alteration (n = 9, 20%); (3) high IFNγ signature score (n = 9, 20%), and (4) low IFNγ signature score (n = 18, 39%). Moreover, these groups were identified using surrogate immunohistochemical markers: EBNA2, PDL1, and IDO1. In conclusion, the molecular studies assessing tumor-host interaction enhances understanding of the EBV+ large B-cell lymphoma spectrum and benefits pathological diagnosis and clinical management.

Endometrial carcinomas can be classified into one of four molecular subtypes, with the POLE-mutant subtype carrying the best prognosis. Pathogenic mutations in POLE are known to disrupt the proofreading function of DNA polymerase epsilon resulting in an ultramutated genome, typically defined as ≥100 mutations per mega-base. Routine Next Generation Sequencing was implemented on all endometrial carcinoma cases at our institution beginning December 2023 to aid in molecular subclassification. During this routine sequencing, six POLE-mutated cases, with confirmed pathogenic POLE mutations, were observed to have a tumor mutation burden (TMB) <100; prior to universal testing only one such case had been identified. Endometrial carcinoma cases with pathogenic POLE mutations and TMB <100 may be globally underrecognized as universal testing is not yet widely standard practice. These cases with pathogenic POLE mutations and a non-ultramutated genome were found to have a lower frequency of classic morphologic "POLE features," including high-grade histology, compared to classic ultramutated cases. The immunohistochemical profiles are also different from ultramutated counterparts, with a lower frequency of MMR IHC abnormalities and p53 null or diffuse staining, and a higher likelihood of strong and diffuse ER/PR expression, aligning with fewer mutations in encoding genes. However, endometrial carcinoma with pathogenic POLE mutations, without ultramutation, appear to retain the "POLE mutational signature" described in the literature. Additionally, clinical outcomes do not appear different; however, this phenomenon needs additional investigation.

Merkel cell carcinoma (MCC) is an aggressive cutaneous tumor that must be distinguished from other cutaneous tumors and metastatic small cell carcinoma. Additional diagnostic markers are limited for MCC with immunophenotypic aberrancy. MCC can display immunohistochemical loss of the epigenetic marker histone H3 lysine 27 trimethylation (H3K27me3), but to our knowledge the diagnostic utility of this observation has not been evaluated. Here we investigate H3K27me3 labeling in MCC (n= 195), cutaneous epithelial tumors (n = 48), non-cutaneous small cell carcinomas (n= 56), and olfactory neuroblastoma (n = 11), comparing with diagnostic markers CK20, neurofilament, SATB2, and POU4F3. H3K27me3 patterns in MCC included global loss, variable/mosaic labeling and diffuse labeling. Global loss significantly associated with polyomavirus negativity, squamous atypia, and sarcomatoid change. Tumors with global loss displayed EZHIP expression (9 cases) and SUZ12 mutation (1 case). Low but retained H3K27me3 labeling was associated with longer overall and MCC-specific survival. Diagnostically, H3K27me3 labeling in MCC was significantly lower than potential mimics, and global loss of H3K27me3 was highly specific for MCC; stronger H3K27me3 labeling was not informative. Considering reduced/absent H3K27me3 as favoring MCC, diagnostic performance was similar to SATB2. However, H3K27me3 displayed consistent performance in MCC with challenging immunophenotypes, unlike SATB2. In summary, we expand upon descriptions of H3K27me3 labeling in MCC and characterize patterns of H3K27me3 in other tumor types including small cell carcinomas and olfactory neuroblastoma. Our findings support diagnostic utility for the widely available marker H3K27me3 in MCC, with weaker labeling favoring MCC over mimics in challenging cases.

Neoadjuvant chemoimmunotherapy (NACi) is a new standard treatment for early-stage high-risk triple-negative breast cancer (TNBC). Desmoplastic reaction (DR) is an important characteristic in the tumor-associated stroma of TNBC. Based on the presence or absence of myxoid stroma and keloid-like collagen bundles within the tumor-associated stroma, DR was classified into immature, intermediate, or mature type. The relationship between DR and NACi efficacy remains unclear. We retrospectively analyzed 209 TNBC patients who received NACi from three medical centers, and 75, 78, and 56 cases were categorized as mature, intermediate, and immature types of DR, respectively. The pathological complete response (pCR) rate was the highest in the mature group (77.3%), followed by the intermediate (30.8%) and immature (17.9%) groups. Multivariate logistic regression analysis indicated that, in addition to histological type, Ki-67, T stage, N stage, and stromal tumor-infiltrating lymphocytes (sTILs), DR was also an independent predictor of pCR. Cases with intermediate and immature stroma exhibited fewer sTILs, an immunosuppressive tumor microenvironment, and upregulation of genes related to extracellular matrix and epithelial-mesenchymal transition. These findings demonstrate the predictive value of DR for NACi efficacy in TNBC and highlight its potential as a histopathological biomarker. The association between DR and molecular hallmarks provides important insights into the biological basis of DR in TNBC.

Gynecologic neuroectodermal tumors either exhibit central nervous system (CNS) differentiation (CNS-like) or represent Ewing sarcoma (EWS) which lacks CNS features and harbors FET-ETS gene fusions. DNA methylation profiling reclassified CNS primitive neuroectodermal tumors into common CNS neoplasms or embryonal tumors with specific epigenetic/ genetic characteristics. Its utility in classifying gynecologic neuroectodermal tumors is unknown. Whole genome DNA methylation profiling was performed on 26 gynecologic neuroectodermal tumors (22 CNS-like tumors, 4 EWS) arising in the ovary, paratubal soft tissue, uterus, and vulva, which were classified by using sarcoma and CNS tumor DNA methylation classifiers. Sarcoma-related gene fusions were confirmed by fluorescence in situ hybridization (FISH) or targeted RNA next generation sequencing (NGS). Tumor only whole exome sequencing (WES) was performed in 13 cases. Copy number alterations and zygosity were inferred from DNA methylation array and WES data. Methylation abnormalities associated with imprinting were examined. The sarcoma methylation classifier identified EWS (n=3) and high-grade endometrial stromal sarcoma (n=1), confirmed by FISH or NGS detection of EWSR1 and YWHAE rearrangements, respectively. The remaining CNS-like tumors were classified by DNA methylation with positive/valid (n=4), indeterminate (n=9), and negative (n=9) scores at family level. Methylation subclasses included teratoma; embryonal tumor with multilayered rosettes, atypical; medulloblastoma, SHH-activated, subtype 3; medulloblastoma, group 3; intraocular medulloepithelioma; supratentorial ependymoma, ZFTA::RELA fused, subclass A; and diffuse pediatric-type high-grade glioma, MYCN subtype. Male gender was predicted in 54% of methylation-confirmed CNS-like tumors and none of the sarcomas. Among CNS-like tumors, copy number analyses identified genome-wide chromosomal gains and losses, and WES revealed genome-wide allelic imbalance suggestive of genome wide duplications. Epigenetic imprinting analyses showed increased paternal or maternal imprinting signal across multiple chromosomes suggesting uniparental duplication. DNA methylation profiling successfully classified gynecologic neuroectodermal tumors as known CNS tumor or sarcoma entities. Epigenetic and exomic studies suggest a male genome and increased maternal allelic contribution in CNS-like tumors, suggesting development via conception or chimerism.

Diagnostic pathology is inherently interpretative and subject to interobserver variability. Although diagnostic concordance is a critical quality metric, distinguishing between acceptable variation, diagnostic error, and professional negligence is essential for both clinical care and medicolegal clarity. This review highlights the difference between interobserver variability (diagnostic disagreement/discordance) that remains within acceptable professional limits, diagnostic error (a deviation from expected standards due to cognitive, technical, or systemic factors), and negligence (a repeated, reckless, or unjustified deviation from established standards). Errors in pathology often reflect systemic vulnerabilities, such as workflow inefficiencies, inadequate quality control, or limited biopsy sampling, rather than individual performance alone. They may occur at any stage of the diagnostic pathway (preanalytical, analytical, or postanalytical) and arise from specimen misidentification, contamination or loss, inadequate sampling, or incomplete documentation. Pathologist-related errors encompass failure to recognize significant pathology, misinterpretation, omission of appropriate ancillary studies, insufficient workup of complex cases, including failure to seek a second opinion, or substandard reporting. Medicolegal implications are heightened when such errors result in delayed diagnosis or major misclassification, leading to patient harm. In breast pathology, interobserver variation in the classification of borderline lesions (eg, grading of phyllodes tumors) and in the interpretation of overlapping entities (eg, atypical apocrine lesions) is well recognized. Although such differences may influence management, they should be regarded as acceptable professional variability, rather than error or negligence. To minimize diagnostic risk and uphold standards, structured reporting, vigilance in complex cases, participation in quality assurance, explicit documentation of uncertainty, active multidisciplinary team engagement, and laboratory accreditation are strongly recommended. Supporting pathologists as diagnosticians and patient safety advocates, within a culture of openness, shared learning, and institutional support, remains central to diagnostic accuracy, transparency, and medicolegal defensibility.