Applied immunohistochemistry & molecular morphology : AIMM最新文献

{"title":"Complementary Diagnostic Value of ZEB1 and CK7 in Renal Oncocytoma and Chromophobe Renal Cell Carcinoma.","authors":"Jelena Filipović, Ivan Soldatović, Maja Životić, Duško Dunđerović, Jovan Jevtić, Gorana Nikolić, Jadranka M Vukajlović, Sanja Radojević-Škodrić","doi":"10.1097/PAI.0000000000001361","DOIUrl":"https://doi.org/10.1097/PAI.0000000000001361","url":null,"abstract":"<p><p>Renal oncocytoma (RO) is a benign renal epithelial tumor that may closely mimic chromophobe renal cell carcinoma (chRCC), particularly in limited biopsy specimens. In addition, the expanding spectrum of oncocytic renal neoplasms further complicates the differential diagnosis. This study included 251 renal epithelial tumors, of which 250 were included in statistical analyses. The cohort comprised RO, chRCC, papillary RCC, clear cell RCC, collecting duct carcinoma, multilocular cystic renal neoplasm of low malignant potential, and a single case of eosinophilic vacuolated tumor (EVT). Tissue microarrays were constructed from formalin-fixed, paraffin-embedded tissue, and immunohistochemical expression of ZEB1, CK7, CD117, AMACR, CD10, GATA3, SDHB, Cathepsin K, and FH was assessed using H-score analysis. Statistical evaluation included 1-way ANOVA, receiver operating characteristic (ROC) curve analysis, and binary logistic regression. RO demonstrated significantly higher ZEB1 expression compared with all other tumor subtypes (P<0.001), while ZEB1 expression was absent in chRCC. The single EVT case, excluded from statistical analysis, also showed no ZEB1 expression. In contrast, CK7 expression was highest in chRCC and minimal in RO. ROC analysis demonstrated excellent diagnostic performance for both markers (ZEB1 AUC=0.941; CK7 AUC=0.945), and combined analysis showed strong discriminatory power, with an overall classification accuracy of 95.5%. ZEB1 represents a promising complementary marker in the differential diagnosis of RO and chRCC. In combination with CK7, it provides a simple and practical immunohistochemical approach that may improve diagnostic accuracy, particularly in limited biopsy specimens. Further validation across the expanding spectrum of oncocytic renal neoplasms is warranted.</p>","PeriodicalId":520562,"journal":{"name":"Applied immunohistochemistry & molecular morphology : AIMM","volume":" ","pages":""},"PeriodicalIF":1.2,"publicationDate":"2026-10-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149187589","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Stromal Fibroblast Activation Protein-α (FAP) as a Potential Adjunctive Biomarker of Invasion in the Transition From Laryngeal High-grade Dysplasia to Squamous Cell Carcinoma.","authors":"Francisco Javier Santaolalla, Jon Danel Solano-Iturri, Juan Carlos López Duque, Beatriz Suárez, Cristina Penas, Arantza Pérez-Dobaran, José I López, Aitor Zabala, Francisco Santaolalla, Gorka Larrinaga","doi":"10.1097/PAI.0000000000001366","DOIUrl":"https://doi.org/10.1097/PAI.0000000000001366","url":null,"abstract":"<p><p>The transition from squamous epithelial dysplasia to invasive laryngeal squamous cell carcinoma (LSCC) is a critical biological and diagnostic step that is difficult to define using morphology alone. Cancer-associated fibroblasts (CAFs) are key mediators of stromal activation during malignant progression, and fibroblast activation protein (FAP) has emerged as a candidate marker of tumor-stroma interaction and invasiveness. We evaluated stromal FAP immunohistochemical expression in laryngeal squamous lesions (n=83), focusing primarily on the diagnostically relevant transition from high-grade dysplasia (HGD, n=23) to invasive LSCC (n=57). The study also included 3 low-grade dysplasias (LGD) to extend the analysis to an earlier stage of noninvasive squamous disease. FAP expression was absent in all LGDs and in 91.3% of HGDs, whereas 93% of LSCCs showed stromal FAP positivity (χ2 test, P=2.3×10-13). Receiver operating characteristic analysis demonstrated high diagnostic accuracy for identifying invasive disease, with a sensitivity of 93%, specificity of 92.3%, and an area under the curve of 0.926 (95% confidence interval: 0.856-0.997). In a subset of HPV-associated carcinomas, focal epithelial FAP expression was also observed. These findings suggest that stromal FAP expression may serve as an adjunctive biomarker to support conventional histopathologic assessment in the recognition of stromal invasion, particularly in the distinction between HGD and invasive LSCC.</p>","PeriodicalId":520562,"journal":{"name":"Applied immunohistochemistry & molecular morphology : AIMM","volume":" ","pages":""},"PeriodicalIF":1.2,"publicationDate":"2026-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149140269","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Punctate Nuclear MLH1 Staining With the VENTANA M1 Clone in Colorectal Carcinoma: Identification of 3 Patterns in Matched Biopsy-Resection Specimens.","authors":"Jacky Z Akhter, Dilshad Dhaliwal, Nasrin Khoshab, Esmeralda C Marginean","doi":"10.1097/PAI.0000000000001348","DOIUrl":"https://doi.org/10.1097/PAI.0000000000001348","url":null,"abstract":"<p><p>In colorectal carcinoma (CRC), deficient DNA mismatch repair (dMMR) is an established predictive and prognostic biomarker and an essential screening marker for Lynch syndrome. Immunohistochemistry (IHC) for MLH1, PMS2, MSH2, and MSH6 is routinely used to assess expression of mismatch repair (MMR) proteins. Strong, homogeneous nuclear staining in tumor cells supports MMR proficiency (pMMR), whereas the absence of tumor nuclear staining in the presence of intact internal controls supports dMMR. Loss of protein expression typically occurs in heterodimeric pairs, most commonly MLH1/PMS2 or MSH2/MSH6, although isolated loss of PMS2 or MSH6 may also occur. A clinically important interpretive pitfall is the punctate or dot-like nuclear staining pattern observed with the VENTANA anti-MLH1 M1 clone. This aberrant pattern represents MLH1 loss but may be misinterpreted as retained MLH1 expression, particularly by pathologists unfamiliar with its significance. We evaluated 24 paired biopsy-resection CRC cases, including 11 MLH1/PMS2-deficient cases in which biopsy specimens showed punctate MLH1 staining with the M1 clone. In the corresponding resection specimens, 3 distinct MLH1 staining patterns were identified: pattern 1, complete loss of nuclear staining throughout the tumor; pattern 2, punctate staining in superficial tumor cells with complete loss in deeper tumor regions; and pattern 3, punctate staining throughout the tumor. Repeat MLH1 IHC using the BioCare Medical G168-15 clone confirmed that punctate nuclear staining with the VENTANA M1 clone corresponds to true MLH1 protein loss. Four cases were initially misinterpreted by the original pathologists, underscoring the clinical impact of this artifact. Our findings indicate that dMMR staining patterns, particularly aberrant MLH1 staining, are more susceptible to interpretive error than conventional retained staining patterns. Recognition of punctate MLH1 staining as a manifestation of MLH1 loss is essential to prevent false MMR-proficient interpretation and to ensure appropriate molecular workup, Lynch syndrome triage, and therapeutic decision-making.</p>","PeriodicalId":520562,"journal":{"name":"Applied immunohistochemistry & molecular morphology : AIMM","volume":" ","pages":""},"PeriodicalIF":1.2,"publicationDate":"2026-10-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149140273","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Interobserver Reproducibility of Treatment-Defining HER2-Low and HER2-Ultralow Immunohistochemical Scoring in Breast Carcinoma: A Systematic Review.","authors":"Vishal Tayade, Gyanendra Singh","doi":"10.1097/PAI.0000000000001364","DOIUrl":"https://doi.org/10.1097/PAI.0000000000001364","url":null,"abstract":"<p><p>Eligibility for trastuzumab deruxtecan now depends on separating HER2 immunohistochemistry (IHC) score 0 from 1+ (HER2-low) and, within score 0, null from ultralow staining-boundaries the assay was not designed to resolve. We systematically identified and appraised studies reporting interobserver or interlaboratory agreement among pathologists for HER2 IHC scoring of breast carcinoma at these contrasts. PubMed/MEDLINE, Scopus, and Web of Science were searched (17 to 18 June 2026) without date or language limits, following a prospectively registered protocol and the PRISMA 2020 guidelines. Two reviewers independently screened records, extracted data verbatim, and appraised quality using QAREL; no values were estimated or imputed. Eighty-nine studies were included: 34 at first submission, and 55 added after an audit of the screening record and retrieval of previously unavailable reports, both completed during revision and disclosed in full. Agreement at the low-end contrasts was consistently lower than for the full HER2 category set: coefficients operationalized directly at 0 versus 1+ ranged from 0.41 to 0.69 across kappa and intraclass-correlation families, per-category coefficients for score 1+ ranged from 0.19 to 0.65, with most below 0.55, and overall multicategory agreement was generally higher (most coefficients 0.43 to 0.85). Agreement for null versus ultralow was examined in 10 of the 89 studies across 4 constructs and was low and spectrum-dependent; in the largest direct examination, per-category κ for ultralow was 0.09 to 0.21. The evidence was fragmented across at least 9 agreement metrics and across binary, per-category, and within-multicategory operationalizations of the same contrast; many studies reported no confidence interval; and no metric family and operationalization was shared by 2 or more studies with a derivable standard error on comparable cohorts. Sixty-two of 89 studies raised some concerns, and 27 were at high risk of bias. Analytical reproducibility at these treatment-defining boundaries is therefore not yet established; the fragmentation that prevents a pooled estimate is itself a finding, underscoring the need for harmonized reporting and analytical validation as priorities.</p>","PeriodicalId":520562,"journal":{"name":"Applied immunohistochemistry & molecular morphology : AIMM","volume":" ","pages":""},"PeriodicalIF":1.2,"publicationDate":"2026-10-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149122617","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Diagnostic Utility of SS18-SSX Fusion-Specific and SSX C-Terminus Antibodies in Synovial Sarcoma: Validation in a Large Indian Tertiary Care Cohort.","authors":"Sahana Khatoon, Balamurugan Thirunavukkarasu, Adarsh W Barwad, Venkatesan S Kumar, Sameer Bakhshi, Ekta Dhamija, Asit R Mridha","doi":"10.1097/PAI.0000000000001363","DOIUrl":"https://doi.org/10.1097/PAI.0000000000001363","url":null,"abstract":"<p><p>Diagnosis of synovial sarcoma (SS) requires molecular confirmation of the SS18-SSX fusion by FISH or RT-PCR, but these methods are costly and limited in resource-constrained settings. Recently developed fusion-specific antibodies offer potential alternatives, but validation in resource-limited settings remains limited. We evaluated SS18-SSX fusion-specific (E9X9V) and SSX C-terminus (E5A2C) antibodies in 50 FISH-confirmed SS cases and 50 histologic mimics from a tertiary cancer center (July 2023 to June 2025). Nuclear staining was scored (0 to 8 scale, grade 0 to 3; grade ≥2 considered positive). Five SS cases had technically noninterpretable SS18-SSX staining and were excluded from the analysis. Sensitivity, specificity, and predictive values were calculated with 95% CIs. SS18-SSX showed 95.6% sensitivity (43/45 interpretable SS cases; 95% CI: 84.9-99.5%) and 100% specificity (50/50 controls). SSX C-terminus demonstrated 100% sensitivity (50/50 SS) but 94.0% specificity (47/50 controls), with false positivity in 3 mimics (medullary thymoma, spindle cell rhabdomyosarcoma, and MPNST). SSX C-terminus showed perfect sensitivity, such that a negative stain effectively excludes synovial sarcoma, whereas SS18-SSX showed perfect specificity, such that a positive stain confirms the diagnosis. Sequential interpretation of both antibodies is a reliable, lower-cost alternative to molecular testing in resource-limited settings, with FISH reserved for indeterminate results.</p>","PeriodicalId":520562,"journal":{"name":"Applied immunohistochemistry & molecular morphology : AIMM","volume":" ","pages":""},"PeriodicalIF":1.2,"publicationDate":"2026-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149122619","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Comparative Evaluation of Immunohistochemistry With DNA Methylation Profiling for Molecular Classification of Medulloblastomas: A Single-Institution Cohort Study.","authors":"Erdener Ozer, Esra Mousa","doi":"10.1097/PAI.0000000000001362","DOIUrl":"https://doi.org/10.1097/PAI.0000000000001362","url":null,"abstract":"<p><p>Medulloblastoma is an embryonal tumor of the central nervous system that is divided into 3 molecular subgroups: WNT-activated, SHH-activated, and non-WNT/non-SHH-activated. The latter comprises group 3 and group 4. Given significant prognostic differences, distinguishing molecular subgroups is important. Although a panel of immunohistochemical markers can be used for grouping, verification of the results with a molecular technique is highly recommended. The aim of this study is to evaluate the performance of immunohistochemistry (IHC)-based molecular grouping with DNA methylation analysis data. The study included 44 cases overall with a histologic diagnosis of medulloblastoma and with optimal-quality extracted tumor DNA. The tumors were grouped into 3 molecular subgroups using IHC for beta-catenin, YAP1, GAB1, and p53. The extracted DNA samples were analyzed using methylation profiling to perform DNA methylation-based molecular grouping. Of 44 cases, methylation profiles matched the defined profiles of medulloblastoma molecular subgroups in 31 cases. Four cases (12.9%) showed a WNT-activated profile, 8 (25.8%) showed an SHH-activated profile, 12 (38.7%) were group 3, and 6 (19.3%) were group 4. In 1 case, differentiation between group 3 and group 4 could not be made. In comparison with IHC-based molecular classification, a discrepancy was found in 7 cases (22.5%), which were initially classified as SHH-activated by IHC but were revealed as WNT-activated, group 3, or group 4 by methylation analysis. We conclude that IHC-based molecular classification of medulloblastomas may yield results that differ from those obtained through methylation profiling-based classification. This discrepancy arises from the lack of a universal cutoff for nuclear beta-catenin positivity and can occur in the SHH-activated group with nondesmoplastic histology, showing focal, weak GAB1 or focal YAP1 immunopositivity. Validated IHC interpretation protocols may help ensure greater accuracy across these 2 techniques.</p>","PeriodicalId":520562,"journal":{"name":"Applied immunohistochemistry & molecular morphology : AIMM","volume":" ","pages":""},"PeriodicalIF":1.2,"publicationDate":"2026-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149083728","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Optimizing Immunohistochemical Detection of Matriglycan in Muscles of Dystroglycanopathy.","authors":"Jason D Tucker, Molly C Holbrook, Simon Zhao, Morgan Drains, Anthony R Blaeser, Qi L Lu","doi":"10.1097/PAI.0000000000001356","DOIUrl":"https://doi.org/10.1097/PAI.0000000000001356","url":null,"abstract":"<p><p>Detection of matriglycan on α-dystroglycan by immunohistochemistry is one of the essential approaches for studying the mechanisms of functional glycosylation of α-DG, the pathogenesis of dystroglycanopathy, and developing experimental therapies. The limited source of matriglycan-specific antibodies of mouse origin, and their low affinity, pose significant difficulty for evaluating the levels and distribution of matriglycan expression, particularly in diseased mouse models. This study describes an optimized procedure with single ethanol fixation of cryosections that creates the strongest and most consistent membrane signal for matriglycan with the IIH6 C4 antibody. This, together with a reduction in background staining, results in optimal contrast between matriglycan signals and background staining in dystrophic muscle tissues. This procedure increases sensitivity for detecting lower levels of matriglycan in situ, in mouse models, and in human muscle. The optimized method is therefore valuable for evaluating experimental therapies preclinically and in clinical trials for all dystroglycanopathies.</p>","PeriodicalId":520562,"journal":{"name":"Applied immunohistochemistry & molecular morphology : AIMM","volume":" ","pages":""},"PeriodicalIF":1.2,"publicationDate":"2026-09-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148979271","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"PRAME as a Diagnostic Adjunct in Clear Cell Sarcoma.","authors":"Banu Yaman, Emine Çeşmecioğlu-Karavin, Tuğçe Aydemir, Hüseyin K Türköz, Hüseyin Kaya, Taner Akalın","doi":"10.1097/PAI.0000000000001360","DOIUrl":"https://doi.org/10.1097/PAI.0000000000001360","url":null,"abstract":"<p><p>Clear cell sarcoma (CCS) is a rare soft tissue neoplasm characterized by melanocytic differentiation and recurrent EWSR1 rearrangements. Owing to its overlapping morphology and immunophenotype with malignant melanoma (MM), distinction between these entities can be challenging, particularly in small biopsies or metastatic settings. Preferentially Expressed Antigen in Melanoma (PRAME) has emerged as a valuable marker in melanocytic pathology; however, its utility in CCS remains to be fully elucidated. We conducted a retrospective analysis of 26 CCS cases from 2 sarcoma referral centers, assessing PRAME immunohistochemistry (IHC) alongside a validation cohort of 120 cutaneous melanomas. Clinicopathologic features, EWSR1 rearrangement status, and survival data were reviewed. The patient cohort (65.4% female) had a mean age of 36.1±15.4 years, with most tumors arising in the extremities. The mean tumor diameter was 4.9±2.8 cm. PRAME was negative in 25/26 (96.2%) CCS cases, with only one case showing focal weak staining. Nineteen CCS cases demonstrated EWSR1 gene rearrangement on molecular analysis. In contrast, PRAME was positive in 110/120 melanomas (91.7%), displaying diffuse (80%) or focal (11.7%) staining. Our findings indicate that PRAME is almost uniformly absent in CCS, in sharp contrast to its strong and prevalent expression in melanoma. PRAME immunohistochemistry may therefore serve as a useful and cost-effective adjunct in the differential diagnosis of melanocytic soft tissue tumors. In an appropriate morphologic and clinical context, the absence of PRAME expression supports a diagnosis of CCS over melanoma, particularly when molecular confirmation of EWSR1 rearrangement is unavailable or inconclusive.</p>","PeriodicalId":520562,"journal":{"name":"Applied immunohistochemistry & molecular morphology : AIMM","volume":" ","pages":""},"PeriodicalIF":1.2,"publicationDate":"2026-09-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148979278","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Autophagy- and Stress-Related Biomarkers in Pretreatment Rectal Adenocarcinoma Biopsies: Associations With Pathologic Response to Neoadjuvant Therapy and Survival.","authors":"Ömer Atmiş, Selin Yurtsever Inan, Hanife Seda Mavili, Fatma Seher Pehlivan, Ahmet Burak Ağaoğlu, Ferhat Ekinci, Özgür Yildirim, Semin Ayhan","doi":"10.1097/PAI.0000000000001358","DOIUrl":"https://doi.org/10.1097/PAI.0000000000001358","url":null,"abstract":"<p><p>Neoadjuvant chemoradiotherapy (nCRT) is the standard treatment for locally advanced rectal adenocarcinoma, yet therapeutic response varies widely and reliable biomarkers are lacking. This study evaluated the immunohistochemical expression of Beclin-1, LC3A, HIF-1α, Bcl-2, and eIF2α in pretreatment biopsies and explored their association with tumor regression grade (TRG) and survival. A retrospective analysis was performed on 53 patients with rectal adenocarcinoma who underwent neoadjuvant therapy and surgical resection between 2010 and 2025. Immunohistochemical expression of 5 markers was evaluated semiquantitatively and correlated with TRG (both Modified Mandard and AJCC systems) and survival outcomes. Among the evaluated markers, only Beclin-1 expression correlated significantly with poorer histopathologic response in both TRG systems (Modified Mandard: ρ=0.35, P=0.010; AJCC: ρ=0.34, P=0.012). ROC analysis confirmed its discriminatory ability (AUC=0.80), identifying high Beclin-1 as a marker of reduced nCRT sensitivity. Lymphovascular invasion (LVI) and perineural invasion (PNI) were also associated with poor response (P=0.002 each). In multivariate analysis, PNI showed borderline significance for nonresponse (OR=4.09, P=0.050). During follow-up, overall survival was adversely affected by LVI, PNI, higher T and N stage, and metastasis (P<0.05). Low eIF2α expression was associated with reduced overall survival (P=0.026), while no marker correlated with disease-free survival. Beclin-1 overexpression may indicate therapy resistance through autophagy-related mechanisms, whereas eIF2α acts as a stress-response marker influencing survival. High Beclin-1 expression may serve as a predictive biomarker of poor nCRT response in rectal adenocarcinoma, while eIF2α shows prognostic significance for overall survival.</p>","PeriodicalId":520562,"journal":{"name":"Applied immunohistochemistry & molecular morphology : AIMM","volume":" ","pages":""},"PeriodicalIF":1.2,"publicationDate":"2026-09-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148979246","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Inflammatory Rhabdomyoblastic Tumor: A Clinicopathological and Immunohistochemical Study of 22 Cases.","authors":"Yingyu Yang, Junqing Yuan, Peipei Zhu, Jian Wang","doi":"10.1097/PAI.0000000000001351","DOIUrl":"https://doi.org/10.1097/PAI.0000000000001351","url":null,"abstract":"<p><p>Inflammatory rhabdomyoblastic tumor (IRMT) is a newly defined subtype of skeletal muscle neoplasm with uncertain malignant potential. Herein, we present a series of 22 IRMT cases to further expand its clinical and pathologic spectrum. This cohort enrolled 20 males and 2 females, with a median age of 42 years (range: 18 to 60 y). The tumors were predominantly located in the deep soft tissues of the lower extremity (n=11, 50%), followed by the trunk (n=4, 18.2%), head and neck region (n=3, 13.6%), upper extremity (n=2, 9%), and abdomen/retroperitoneum (n=2, 9%). Most patients presented with a slowly growing, deeply seated soft tissue mass, with a median diameter of 6 cm (range: 3 to 23 cm). Histologically, 12 cases (54.5%) showed a spindled to pleomorphic morphology, 7 cases (32%) exhibited a monomorphic spindled morphology, and 3 cases (13.6%) displayed a spindled to epithelioid phenotype. All lesions were characterized by dense inflammatory and histiocytic infiltrates. Focal calcification, cholesterol clefts, and histiocytic necrosis were noted in a subset of cases. Three cases demonstrated progression to rhabdomyosarcoma. Immunohistochemically, all tumors exhibited diffuse and strong desmin expression, with variable MyoD1 immunoreactivity and limited myogenin staining. Molecular analysis identified somatic mutations in NF1 (n=4), TP53 (n=2), and KRAS (n=1) genes among the tested cases. With a median follow-up of 17.5 months (range: 3 to 77 mo) in 22 patients, 2 cases with rhabdomyosarcomatous transformation developed lung metastases, whereas the remaining patients remained disease-free following complete surgical resection. Our study further validates IRMT as a distinct myogenic neoplasm with an indolent behavior. Correlation of clinical manifestations and morphologic features with ancillary studies is essential to avoid overdiagnosing IRMT as a high-grade rhabdomyosarcoma.</p>","PeriodicalId":520562,"journal":{"name":"Applied immunohistochemistry & molecular morphology : AIMM","volume":" ","pages":""},"PeriodicalIF":1.2,"publicationDate":"2026-09-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148979273","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}