Endometrial cancer (EC) is a major gynecologic malignancy whose classification and treatment paradigms are evolving because of molecular profiling. Mutations in DNA polymerases, particularly in DNA polymerase epsilon ( POLE ) and DNA polymerase delta 1 ( POLD1 ), have become central to a subset of ultramutated ECs with crucial clinical and prognostic effects. The molecular mechanisms of POLD1 dysfunction in EC, its clinical manifestations, emerging diagnostic challenges, and therapeutic opportunities are explored in this review. Mutations in the exonuclease domain of POLD1 lead to ultramutation. Recent evidence suggests a unique recessive mechanism where an oncogenic mutation is coupled with the loss of the wild-type allele, abrogating the cell’s ability to correct replication errors. Mutations in 4 conserved acidic residues (D316, E318, D402, and D515)—the DEDD motif—such as p. D402N result in the loss of proofreading capacity and confer a high tumor mutational burden. Small nuclear ribonucleoprotein polypeptide B overexpression in EC also modulates POLD1 splicing, contributing to its oncogenicity. POLD1 -mutant ECs probably represent a subset of the ultramutated molecular category, paralleling POLE -mutated tumors, with implications for diagnostics, genetic counseling, and targeted therapy; their identification necessitates expanded genomic testing, mutational signature analysis, and awareness of their unique splicing and functional biology.
The approval of Mirvetuximab soravtansine, a folate receptor alpha (FOLR1)-targeting antibody-drug conjugate, for platinum-resistant ovarian cancer, has prompted interest in FOLR1 as a target in endometrial carcinoma (EC). Characterization of FOLR1 expression across EC histotypes, TCGA molecular subtypes, and clinically relevant biomarkers using the FDA-approved companion diagnostic assay has not been performed. FOLR1 immunohistochemistry was performed on tissue microarrays from 169 molecularly classified ECs using the VENTANA FOLR1-2.1 assay and scored by proportion score PS2 and PS1 criteria at the ovarian cancer eligibility cutoff (PS2 ≥75) as well as exploratory thresholds. Associations with histotype, molecular subtype, biomarker (ER, PR, HER2) status, survival outcomes, intratumoral heterogeneity, and matched primary-recurrence expression were assessed. Only 3% (5/169) of ECs met the PS2 ≥75 threshold; all 5 were p53-abnormal (p53abn). In all, 9% (15/169) showed PS2 ≥25, predominantly in p53abn and no specific molecular profile (NSMP) subgroups. Uterine serous carcinoma had the highest expression; FOLR1 was absent in 3/3 clear cell carcinomas. Higher FOLR1 expression was associated with inferior survival, though this largely reflected molecular subtype and grade. FOLR1 was homogeneous across cores but variable between primary and recurrent tumors. FOLR1 testing in EC may be most relevant in p53abn and NSMP tumors and may not be useful in clear cell carcinomas. FOLR1 may have prognostic value in low-grade endometrioid and ER/PR-positive EC. Retesting at tumor recurrence is recommended. Given the frequency of lower-level FOLR1 expression, trials with treatment-response data are needed to test eligibility criteria below the current ovarian cancer threshold.
We report a case of a uterine mesenchymal tumor with myogenic differentiation and SRF::RELA fusion occurring in a 23-year-old woman manifesting as an endometrial polyp. The tumor consisted of bland spindle cells with a predominantly fascicular growth pattern and entrapment of the endometrial glands and vessels. The tumor was positive for smooth muscle markers and CD10. NGS RNA analysis revealed SRF::RELA fusion. NGS DNA analysis revealed no pathogenic variants or copy-number alterations. On follow-up 12 months after curettage, the patient showed no signs of the disease. To the best of our knowledge, only 3 cases of uterine tumors with SRF::RELA fusion arising in the gynecologic tract have been described previously, and all show benign behavior so far. Differential diagnosis includes both benign and potentially aggressive entities, such as leiomyoma, inflammatory myofibroblastic tumor, perivascular epithelioid cell tumor, uterine adenosarcoma, low-grade endometrial stromal sarcoma, and uterine sarcoma with KAT6B/A::KANSL1 fusion.
Mirvetuximab soravtansine is an antibody-drug conjugate targeting FRα, which has not only shown antitumor activity and tolerability in ovarian carcinoma with FRα high expression, but has also been incorporated into NCCN guidelines to treat patients with platinum-resistant disease. Sequential cases were retrieved from a previously published cohort of gynecologic pathology cases in which FOLR1 immunohistochemistry had been performed at our institution. Clinical and pathologic data collected included patients' age, tumor histotype, tumor grade (if reported or relevant to histotype), primary tumor site, FIGO stage, and type of specimen. FOLR1 immunohistochemical results were collected from the report, including the overall tumor percentage and intensity reported, and subsequently determined if this was an overall positive or negative result (positivity defined as per current recommendations for therapy eligibility, 75%, 2-3+ intensity). The FOLR1 immunohistochemical slide was reviewed by 2 gynecologic pathologists and jointly recorded the following parameters: percent of cells staining at each level of intensity (0-3), range of staining intensity (0-3), percent of cells with membranous, cytoplasmic, or mixed staining, apical-only versus any membranous staining, percent of cells with complete membranous staining, and presence of abrupt transition (0 - no staining at all, juxtaposed to 2-3+ staining). One hundred twenty cases were reviewed and scored, 119 of which had original reported scores available for comparison. The staining intensity record was 0 in 9 (7.5%) of the cases, 0-1 in 3 (2.5%), 0-2 in 11 (9.2%), 0-3 in 88 (73.3%), 1-3 in 3 (2.5%), 2-3 in 4 (3.3%), and 3 in 2 (1.7%). The percent of positive cells at 2-3+ intensity as per quartile of cases was 12 (10.0%) cases with 0%, 14 (11.7%) cases with 1%-24%, 15 (12.5%) with 25%-49%, 28 (23.3%) with 50%-74%, and 51 (42.5%) with ≥75%. Using the original clinical reports, 67 (56.3%) of 119 cases were positive; 55 (67.9%) of 81 resection cases were positive, while 12 (31.6%) of 38 biopsy cases were positive. On re-review, 51 (42.5%) of all 120 cases were positive, with 41 (50%) of 82 resection cases being positive and 10 (26.3%) of 38 biopsy cases being positive. Overall, 18 (15.1%) of 119 cases had a clinically significant change (i.e. positive to negative or negative to positive). When broken down by type of specimen, 16 (19.8%) of 81 resection cases had a significant change, while only 2 (5.3%) of 38 biopsy cases had a significant change. Of the original scores taken from the report, the score was clearly stated in 117 reports, of which 47 cases were reported within 65% to 85% 2-3+ intensity. Seventeen of these 47 on rescoring were changed significantly as to a clinical action outcome; all 17 of these were changed from "positive" to "negative." The 18th case, which was changed on rescoring, was the singular case that was changed from "negative" to "positive," which was originally reported at 60% and on review was scored 75%. On rescoring of all 120 cases, 32 cases were 65% to 85% 2-3+ intensity. The heterogeneous staining pattern of FRα expression may lead to difficulties in scoring and interpretation, which can have an impact on clinical management.
Adenoma malignum-like (AM-L) pattern is the least common invasion type in endometrioid carcinoma of the uterus and is characterized by a bland morphologic appearance in accordance with International Federation of Gynecology and Obstetrics Grade 1 endometrioid carcinoma. However, the biological behavior of the AM-L pattern is not always indolent, and it may present at an advanced tumor stage. Although several studies have described the clinicopathological features of this pattern, the molecular alterations have not yet been explored. Here, we report a case of endometrioid carcinoma with AM-L invasion pattern and analyzed its genetic alterations using a next-generation sequencing panel that included 571 genes. Six single nucleotide variations or insertion/deletion alterations were detected, including ARID1A exon 4 c.1848dup p.(S617Lfs*6), CTNNB1 exon 3 c.101G>A p.(G34E), PTEN exon 5 c.332G>A p.(W111*), PTEN exon 6 c.548dup p.(N184Efs*6), BCOR exon 10 c.4376A>G p.(N1459S), and MAPK4 exon 6 c.1594G>A p.(G532S). Neither POLE nor TP53 alteration was detected. No copy number variations or gene fusions were observed. The microsatellite status was stable, and the tumor mutational burden was low. The molecular features demonstrate the endometrioid nature of the AM-L pattern. Further studies are needed to explore the significance of these genetic alterations in this particular pattern and to clarify their oncogenic mechanism.
Mesonephric-like carcinosarcoma (MLCS) is an uncommon gynecologic malignancy comprising mesonephric-like adenocarcinomatous (MLA) and high-grade (HG) sarcomatous elements. We describe an endometrial MLCS in a 63-yr-old woman showing divergent p53 immunohistochemical expression, with abnormal expression in the MLA component and normal expression in the sarcomatous component. Dedifferentiated carcinoma and uterine mesenchymal tumors are primary differential diagnoses when sarcomatous elements predominate or exhibit round-cell morphology. A review of 25 endometrial MLCS cases, including ours, showed advanced-stage presentation in 48% (12/25), recurrence in 60% (15/25) and disease-related death in 28% (7/25) of cases, underscoring its aggressive behavior. Heterologous differentiation occurred in 16% of cases but was not essential for diagnosis when unequivocal HG sarcomatous cells were present. Component-specific next-generation sequencing of our case revealed identical KRAS, TP53, and RB1 mutations in both components, with additional PTPRT mutation and KLF5 amplification restricted to the MLA component, representing a novel molecular signature with potential therapeutic implications.
As an update to the 2021 guidelines, the 2025 endometrial carcinoma risk classification by the European Society of Gynaecological Oncology (ESGO), the European Society for Radiotherapy and Oncology (ESTRO), and the European Society of Pathology (ESP) combines grade 3 endometrioid and nonendometrioid carcinomas into a single "high-grade" category and indicates that, within the mismatch repair-deficient (MMRd) molecular subgroup, tumor grade has limited relevance. We evaluated the prognostic value of tumor grade within the 2025 ESGO-ESTRO-ESP framework in a retrospective, single-center cohort of 1115 patients (median follow-up: 69 mo). Molecular classification and estrogen receptor status were determined by immunohistochemistry and polymerase-ε (POLE) sequencing. A 3-category histopathologic classification (grade 1-2 endometrioid, grade 3 endometrioid, and nonendometrioid) was associated with survival within MMRd, no-specific-molecular-profile (NSMP), and p53-abnormal subgroups. Analyses were not feasible in POLE ultramutated carcinomas. Within the MMRd and NSMP groups, disease-specific survival did not differ between grade 3 endometrioid and nonendometrioid carcinomas, supporting their combination into a single high-grade category for adjusted analysis. In localized MMRd tumors, deep myometrial invasion, cervical stromal invasion, and focal or substantial lymphovascular space invasion (LVSI) were associated with poor survival. In localized NSMP tumors, the pooled high-grade category and substantial LVSI predicted poor survival, with similar outcomes observed in stage IIB and IIC tumors. We confirm the lack of independent prognostic impact of grade in MMRd, as reflected in the guidelines. In NSMP, substantial LVSI but not estrogen receptor status has prognostic value beyond grade, supporting refinement of risk stratification in clinical practice.
Anastomosing hemangioma is a benign vascular neoplasm originally described in the genitourinary tract, but subsequently reported in a variety of anatomic sites. Although ovarian involvement has been documented, bilateral localization has not yet been reported in the English literature. Here, we describe the case of a 67-year-old woman with a strong clinical suspicion of advanced ovarian carcinoma, in whom histologic examination revealed bilateral ovarian anastomosing hemangioma. Frozen section evaluation did not allow a definitive diagnosis; however, on permanent sections, characteristic diagnostic features-such as foci of extramedullary hematopoiesis and scattered fibrin thrombi-became evident, enabling the correct classification. This report highlights the peculiar presentation of bilateral ovarian anastomosing hemangioma, aiming to increase awareness of this rare entity and to emphasize the diagnostic challenges it may pose, particularly during intraoperative consultation.
This report pertains to a rare case of cervical squamous cell carcinoma (SCC) with choriocarcinomatous (CC) differentiation in a 77-yr-old woman. The patient developed lung and mediastinal metastases 3 mo after surgery and died at 5 mo. Histopathologically, the tumor shows a mixed pattern of SCC and CCs. Both SCC and CC components showed a mutant-type p53 immunostaining and no high-risk HPV mRNA signals by RNAscope. PD-L1 was positive in SCC and CC, with a combined positive score of 10 and 90, respectively. Short tandem repeat analysis indicated identical alleles among CC, SCC, and the normal tissues. Targeted next-generation sequencing demonstrated high tumor mutational burden (>10 mutations/Mb) and 2 common driver mutations [TP53 (c.853G>A) and TERT (c.-146C>T)]. This is the first report of an HPV-independent cervical SCC with choriocarcinomatous differentiation, supporting a clonal origin with divergent differentiation, and suggesting comprehensive therapies combining immunotherapy and pathway inhibitors for this aggressive cancer.
Adult granulosa cell tumor (AGCT) is a pure-type sex cord tumor of the ovary that shows a low-grade morphology. Despite being classified as malignant, it typically demonstrates indolent clinical behavior. Histologic grading is not traditionally useful for prognostication, as most tumors are low-grade with multiple morphologically bland patterns. However, high-grade transformation, characterized by marked cytologic atypia and elevated mitotic activity, is considered indicative of aggressive clinical behavior. This high-grade transformation is closely associated with TP53 abnormalities detected by p53 immunohistochemistry. We herein describe a case of AGCT with p53 overexpression in the absence of an anaplastic or high-grade morphology. The findings of this case show that high-grade genomic alterations, including TP53 abnormalities, may occur earlier in the tumorigenic process of AGCT, even before the development of overt high-grade morphologic features. Further accumulation and analysis of similar cases are required to clarify the clinicopathological significance of p53 abnormalities in AGCT.
Nodular fasciitis (NF) is a benign, self-limited myofibroblastic proliferation that typically arises in the subcutaneous tissues of the extremities and trunk, while vulvar involvement is distinctly rare. Owing to its rapid growth and histologic features, NF may mimic both benign and malignant lesions, creating significant diagnostic challenges. We report a case of a 34-yr-old woman presenting with a rapidly enlarging, painless vulvar mass initially suspected to represent a Bartholin gland cyst. Gross examination revealed a 2.5 cm, well-defined lesion with a tan, glistening cut surface. Microscopically, the lesion was unencapsulated and composed of spindle cells arranged in a storiform pattern with alternating cellularity, set within a myxoid and collagenous stroma. Extravasated erythrocytes and occasional osteoclast-like giant cells were present, while cytologic atypia and necrosis were absent. Mitotic activity was low. Immunohistochemically, the lesion showed diffuse smooth muscle actin expression and was negative for CD34, desmin, ALK, cytokeratin, estrogen receptor, progesterone receptor, and STAT6 with retained RB1 expression and membranous β-catenin staining. Next-generation sequencing identified a MYH9:::USP6 fusion, confirming the diagnosis. This case highlights the importance of recognizing nodular fasciitis in the vulva as a potential diagnostic pitfall, particularly in lesions clinically interpreted as Bartholin gland cysts. Integration of morphologic, immunohistochemical, and molecular findings is essential to avoid misdiagnosis and overtreatment.
High-grade endometrial stromal sarcoma (HGESS) is a rare tumor that typically occurs over a wide age range, from 14 to 71 yr, often presenting with nonspecific clinical symptoms. This tumor group displays heterogeneous tumor morphology and a growing number of molecular alterations. The most common alterations are YWHAE::NUTM2 fusion and BCOR gene alterations, including fusions and internal tandem duplications. Here, we report a HGESS with a novel ING3::BCOR fusion. A 74-yr-old female presented with vaginal bleeding and underwent myomectomy. Hematoxylin & eosin (H&E) sections revealed a spindle cell proliferation with both hypocellular and hypercellular areas. Cytologic atypia was mild to moderate, with a mitotic count of 5/10 high-power fields; the background stroma had focal myxoid and collagenous changes. Focal necrosis and pleomorphism were observed. Ancillary studies showed CD10 and diffuse cyclin D1 positivity by immunohistochemistry (IHC). Estrogen receptor (ER), progesterone receptor (PR), ALK1, S100, HMB45, and CD34 were negative and p53 showed a wild-type staining pattern. RNA-based next-generation sequencing showed an ING3::BCOR fusion, confirming the diagnosis of HGESS with ING3::BCOR fusion. HGESS is an evolving entity with an increasing number of genetic alterations, including genetic fusion involving the BCOR gene. HGESS with BCOR fusion should be considered in tumors with a combination of spindle cell growth, myxoid background, foci of coagulative necrosis, diffuse cyclin D1 positivity, and a negative hormone receptor status. Accurate diagnosis requires an integrated approach that combines histopathologic evaluation, IHC, and molecular testing.
Preferentially expressed antigen in melanoma (PRAME) immunohistochemistry was initially used diagnostically in melanoma but is increasingly evaluated across malignancies for diagnostic, prognostic, and therapeutic purposes. PRAME protein acts as a dominant repressor of retinoic acid signaling and may help stratify patients for retinoic acid-based therapy. Multiple PRAME-targeted immunotherapy trials are ongoing, supported by its selective tumor expression. Vulvar intraepithelial neoplasia (VIN) is an appealing setting for PRAME assessment because lesions are often multifocal or extensive, and treatment by excision can be disfiguring. Immunotherapy is also of rising interest in advanced vulvar squamous cell carcinoma (VSCC). We aimed to evaluate PRAME expression in HPV-associated and differentiated vulvar intraepithelial neoplasia (dVIN)-associated squamous lesions of the vulva. Full tissue sections from 106 vulvar squamous neoplasms (31 HSIL, 29 VSCC arising in HSIL, 20 dVIN, 26 VSCC arising in dVIN) were stained with PRAME antibody. Expression was recorded as the percentage of positive tumor cells, with intensity (0-3+) and staining localization documented, and an H-score was subsequently calculated. Groups were compared using the Wilcoxon rank-sum or Kruskal-Wallis tests. Most VSCCs (78%) expressed PRAME, with significantly higher expression in dVIN-associated lesions (P=0.006). Subgroup analysis showed the highest PRAME expression in dVIN-associated VSCC and the lowest in HSIL (P<0.00001). These findings suggest that distinct biological drivers of HPV-associated and dVIN-associated vulvar neoplasia contribute to differential PRAME expression. The strongest expression in dVIN-associated VSCC highlights a possible link between aggressive tumor behavior and PRAME. dVIN-associated lesions may therefore represent promising candidates for PRAME-targeted therapy.
Although tumor budding has emerged as an indicator of tumor aggressiveness in several solid cancers, its prognostic significance in endometrial cancer is not well studied. This systematic review and meta-analysis aimed to quantify the association between tumor budding and clinicopathologic parameters in endometrial cancer. A comprehensive search of electronic databases was performed from inception to December 2025, and clinicopathologic data were extracted from studies that included patients with histologically confirmed endometrial cancer, assessed tumor budding on histopathology, reported clinicopathologic outcomes and/or survival outcomes, and provided effect estimates or sufficient data to calculate odds ratios or hazard ratios. In the pooled analysis of data from 12 eligible studies, tumor budding was found to be significantly associated with lymphovascular space invasion, lymph node metastasis, high tumor grade and deep myometrial invasion ≥50% but not with advanced-stage disease at presentation and cervical stromal invasion. To conclude, though tumor budding is significantly associated with adverse clinicopathologic features in endometrial carcinoma, standardization of assessment methods and prospective validation are needed before routine clinical implementation as a predictive tool.
A new concept of molecular classification for clear cell ovarian carcinoma (CCOC) has been proposed: TP53 wild-type and TP53 mutated. Our aim was to evaluate this classification at the immunohistochemical level in p53 normal and abnormal subgroups. Clinicopathologic factors and 12 immunohistochemical biomarkers (p53, PR, ER, β-catenin, vimentin, ARID1A, HNF1-β, E-cadherin, c-erb-B2, MIB-1, p16, and L1CAM) and patient prognosis were analyzed in 132 CCOCs. The p53 abnormal group presented with significantly worse disease-specific overall survival (DSS) and disease-free survival (DFS) than the p53 normal group, which was largely due to higher stage and a more frequent presence of residual tumor in the p53 abnormal group. Furthermore, higher stage and presence of residual tumor were markers of poor outcome within both p53 subgroups. Interestingly, the presence of ascites was related to shorter DSS only in p53 normal cases. The p53 normal group was also characterized by a higher frequency of ARID1A loss and HNF1-β positivity, whereas p16 overexpression and ER positivity were more common in p53 abnormal cases. Interestingly, ARID1A loss correlated with poor DSS in the p53 abnormal group. In the p53 normal tumors, ER positivity was associated with better DSS and p16 positivity with worse DFS. L1CAM positivity was associated with residual tumor only in the p53 normal group. Our findings support the existence of 2 distinct molecular subgroups of CCOC, p53 normal and p53 abnormal, with diverse characteristics and patient outcomes. Clinical and molecular differences were discovered within these subgroups.
Myxoid inflammatory myofibroblastic sarcoma (MIMS) is a recently described aggressive sarcoma with deceptively bland spindled cells with a myofibroblastic phenotype and myxoid stroma. These tumors are negative for ALK gene rearrangements, but have been shown to harbor gene fusions involving PDGFRA/B , JAK1 , and PML and/or mutations involving KRAS . Only one uterine case has been previously reported. Here we report the second case of uterine MIMS. This tumor arose in a 40-yr-old woman patient and showed a conspicuously whorled architecture with myxoid stroma and so-called organoid aggregates. By immunohistochemistry, the tumor was positive for CD10, estrogen receptor (ER), and progesterone receptor (PR) with focal smooth muscle actin expression and no staining for ALK, desmin, h-caldesmon, HMB-45, or cathepsin-K. Next-generation sequencing analysis revealed the presence of 2 pathogenic mutations in KRAS , as well as pathogenic mutations in RAD51B and LATS1 . No gene fusions in PDGFRA/B , JAK1 , PML , ALK, ROS1, PLAG1 , or any other gene were identified by whole transcriptomic RNA sequencing. Given its deceptively bland appearance and its propensity, at least in the uterus, to express both CD10 and ER with only focal SMA expression, MIMS can be mistaken for an endometrial stromal tumor, an ALK and ROS1 -negative uterine inflammatory myofibroblastic tumor, or other cytologically bland fusion-driven uterine mesenchymal neoplasms.
Mullerian adenosarcomas are biphasic tumors with benign epithelium and malignant stroma, typically found in the uterine corpus but rarely in the cervix, ovaries and other locations. A diagnostic pitfall is misdiagnosis as benign polyps due to bland cytology. Sarcomatous overgrowth (SO) and myometrial invasion are poor prognosticators. A positive prognosticator may be stalked tumors. Surgery alone can yield favorable outcomes. Here, we present a rare case of Mullerian adenosarcoma of the cervix in a 74-yr-old patient with p53 wild-type, high-grade SO that presented as a cervical polyp with a stalk.
Endometrial serous carcinoma (ESC) and high-grade ovarian serous carcinoma (HG-OSC) share morphologic, immunohistochemical, and molecular features, and the determination of the primary tumor site is challenging, particularly in cases with both uterine and ovarian involvement. This study aimed to evaluate the diagnostic utility of MUC4 protein expression for distinguishing ESC from HG-OSC. We retrospectively analyzed 79 resection specimens, comprising 36 ESC and 43 HG-OSC cases, including an additional 39 samples from extraprimary sites obtained from 6 ESC and 18 HG-OSC cases, which were also incorporated into the study. Immunohistochemical expression of MUC4 and WT1 was quantified as the percentage of positive tumor cells. Statistical analyses included the Mann-Whitney U test, independent samples t-test, χ2 test, Phi contingency coefficient, and multivariable binary logistic regression to assess the independent predictive value of MUC4 and WT1 for tumor origin. MUC4 expression was significantly more frequent in ESC than in HG-OSC (n=29/36, 81% patients in ESC vs. n=11/43, 26% in HG-OSC, P <0.001), whereas WT1 expression was predominantly observed in HG-OSC (n=37/41, 90% in HG-OSC vs. n=10/33, 30% in ESC, P<0.001). MUC4 expression was detected in all cases with an in-situ component associated with invasive ESC (n=5, 100%). Combined immunophenotypic analysis showed that the WT1-/MUC4+ profile was strongly associated with ESC (n=18/33, 55%), whereas the WT1+/MUC4- profile was characteristic of HG-OSC (n=32/41, 78%) (P<0.001). In multivariable logistic regression, MUC4 positivity was independently associated with endometrial origin (OR=20.5, 95% CI: 4.99-83.68, P<0.001), whereas WT1 positivity was associated with a decreased likelihood of endometrial origin (OR=0.12, 95% CI: 0.03-0.45, P=0.002). The optimal cut-off value was determined as ≤10% for MUC4, yielding a sensitivity of 86.0% and specificity of 77.8% (Youden index: 0.638), and ≥5% for WT1, with a sensitivity of 90.2% and specificity of 68.6%. Notably, the combined model showed superior diagnostic performance compared with either marker alone, with an AUC of 0.900 (95% CI: 0.820-0.964). At the optimal cut-off (≥0.513), the combined model achieved a sensitivity of 95.1% and specificity of 72.7%, indicating improved overall accuracy in differentiating between ESC and HG-OSC. This study demonstrates that MUC4, previously identified as differentially expressed in TCGA transcriptomic data, may have significant diagnostic value for distinguishing ESC from HG-OSC, both in the primary tumor site and in areas of multifocal involvement. MUC4, particularly when combined with WT1, is a promising immunohistochemical marker that may support accurate determination of tumor origin and may aid in diagnosis in challenging cases. Further validation in larger cohorts is warranted.
