Prognostic impact of lymph node invasion levels in patients with bladder cancer undergoing radical cystectomy and pelvic lymphadenectomy.

Extranodal extension in metastatic lymph nodes (LNs) is a poor prognostic factor in bladder cancer (BC). Furthermore, cancer invasion levels in sentinel LNs are associated with prognosis in melanoma. The present study aimed to evaluate the LN invasion level, defined as the extent of cancer invasion in anatomical and immunological LN substructures, and compare it with the pathological node (pN) stage of the tumor-node-metastasis staging system in BC. A total of 98 patients with BC who underwent radical cystectomy and pelvic lymphadenectomy were retrospectively assessed. The LN invasion level was classified as follows: Level 0, no cancer cell within the resected LNs; Level 1, cancer cells confined to intracapsular lymph vessels and subcapsular or transverse sinuses; Level 2, cancer cells infiltrating the cortex, paracortex or medulla; and Level 3, cancer cells infiltrating or beyond the LN capsule. The proportion of patients with Levels 0, 1, 2 and 3 was 70.4% (69/98), 8.2% (8/98), 14.3% (14/98) and 7.1% (7/98), respectively. Kaplan-Meier survival curves of recurrence-free survival (RFS), cancer-specific survival (CSS) and overall survival (OS) with LN invasion levels better stratified outcome patient when using Levels 1-3 compared with pN1-3. In addition, LN invasion levels better predicted RFS, CSS and OS, in comparison with the pN stage (c-index of 0.672 vs. 0.646, 0.688 vs. 0.665, and 0.702 vs. 0.661, respectively). Finally, multivariate analysis revealed that the predictive accuracy of the model integrating pathological tumor (pT) stage and LN invasion levels in RFS, CSS and OS was greater than that of the conventional model that included pT and pN stage (c-index of 0.723 vs. 0.703, 0.710 vs. 0.694, and 0.725 vs. 0.692, respectively). In conclusion, the model with LN invasion levels accurately predicted the prognosis of patients with BC after radical cystectomy and pelvic lymphadenectomy.

Prognostic impact of combination therapy with gemcitabine and cisplatin plus S-1 and subsequent conversion surgery for initially unresectable upper biliary tract cancers.

PURPOSE AND BACKGROUND: For the past decade, there have been few chemotherapy options for unresectable biliary tract cancer (BTC). Recently, however, combination therapy with gemcitabine and cisplatin plus S-1 (GCS) has been identified as a promising strategy. This retrospective study analyzes the clinical results of GCS therapy and subsequent conversion surgery (CS). METHOD: We analyzed the clinical data of 60 consecutive patients who received GCS therapy for unresectable upper BTC at our university hospital during the 5 years between September, 2018 and December, 2022. RESULTS: All patients received GCS therapy as first-line chemotherapy. The response rate was 33.9% and subsequent CS was performed in 35.0%. Of the patients who underwent CS, 81% required more than bisectionectomy of the liver with extrahepatic bile duct resection. The median overall survival of the patients who received GCS therapy and underwent subsequent CS was significantly longer than that of the patients who received GCS therapy alone (28.0 months vs. 12.4 months, respectively; p < 0.001). A decrease in the CA19-9 level 1 month after chemotherapy and RECIST PR were independent positive predictors of CS, whereas unresectable gallbladder cancer and pretreatment ALBI grade 3 were negative predictors of CS. CONCLUSION: GCS therapy and subsequent CS may contribute to the longer term survival of patients with unresectable upper BTC.

Impact of LAG-3/FGL1 pathway on immune evasive contexture and clinical outcomes in advanced urothelial carcinoma.

BACKGROUND: Anti-programmed death-1 (PD-1)/anti-PD-ligand-1 (PD-L1) pathway inhibition is a standard regimen for advanced urothelial carcinoma (UC); however, its limited efficacy has been reflected in reported medium response rates. This study explored the role of next-generation coinhibitory receptors (IRs; lymphocyte activation gene 3 (LAG-3), T-cell immunoglobulin and mucin domain 3 (TIM-3), and T-cell immunoreceptor with Ig and ITIM domains (TIGIT)) and their ligands (LGs) in the response to PD-(L)1 blockade therapy and the oncological outcomes in patients with UC. METHODS: We investigated metastatic UC cases who underwent PD-(L)1 therapy (cohort 1: n=348, cohort 2: n=89, and cohort 4: n=29) or advanced UC cases involving surgery (cohort 3: n=293 and cohort 5: n=90). We assessed the mRNA expression profiles and corresponding clinical information regarding IRs and LGs using cohorts 1, 2, and 3. Additionally, we elucidated the spatial features of these targeted markers using multiplex immunohistochemistry (mIHC) on formalin-fixed paraffin-embedded samples from cohorts 4 and 5. Survival, differential expressed gene, and Gene Set Enrichment analyses were performed. For mIHC, quantitative analyses were also performed to correlate immune and tumor cell densities with patient survival. RESULTS: LAG-3 expression was strongly associated with the responsiveness of PD-(L)1 blockade compared with the expression of TIM-3 and TIGIT. In tumors with high LAG-3 levels, the increased expression of fibrinogen-like protein 1 (FGL1) had a significantly negative effect on the response to PD-(L)1 blockade and overall survival. Moreover, high FGL1 levels were associated with elevated CD4+ regulatory T-cell gene signatures and the upregulation of CD39 and neuropilin-1, with both indicating CD8+ T-cell exhaustion. mIHC analyses revealed that patients with stromal CD8+LAG-3+cellshigh-tumor FGL1+cellshigh exhibited a significant negative correlation with survival rates compared with those with stromal CD8+LAG-3+cellshigh-tumor FGL1+cellslow. CONCLUSIONS: LAG-3 expression and high FGL1 coexpression are important predictive factors of adverse oncological outcomes related to the presence of immunosuppressive contextures. These findings are hypothesis-generating, warranting further mechanistic and clinical studies aimed to evaluate LAG-3/FGL1 blockade in UC.

Diagnostic performance of photodynamic diagnosis with oral 5-aminolevulinic acid for upper tract- and bladder urothelial carcinoma: a single-centre, retrospective analysis.

PURPOSE: To compare the diagnostic performance of photodynamic diagnosis (PDD) enhanced with oral 5-aminolaevulinic acid between the suspected upper tract urothelial carcinoma (UTUC) and bladder urothelial carcinoma (BUC) cases. METHODS: This retrospective study included 18 patients with suspected UTUC who underwent ureteroscopy (URS) with oral 5-ALA in the PDD-URS cohort between June 2018 and January 2019; and 110 patients with suspected BUC who underwent transurethral resection of bladder tumour (TURBT) in the PDD-TURBT cohort between January 2019 and March 2023. Sixty-three and 708 biopsy samples were collected during diagnostic URS and TURBT, respectively. The diagnostic accuracy of white light (WL) and PDD in the two cohorts was evaluated, and false PDD-positive samples were pathologically re-evaluated. RESULTS: The area under the receiver operating characteristic curve (AUC) of PDD was significantly superior to that of WL in both cohorts. The per biopsy sensitivity, specificity, and positive and negative predictive values of PDD in patients in the PDD-URS and PDD-TURBT cohorts were 91.2 vs. 71.4, 75.9 vs. 75.3, 81.6 vs. 66.3, and 88.0 vs. 79.4%, respectively. The PDD-URS cohort exhibited a higher AUC than did the PDD-TURBT cohort (0.84 vs. 0.73). Seven of four false PDD-positive samples (57.1%) in the PDD-URS cohort showed potential precancerous findings compared with eight of 101 (7.9%) in the PDD-TURBT cohort. CONCLUSION: The diagnostic performance of PDD in the PDD-URS cohort was at least equivalent to that in the PDD-TURBT cohort.

Development and Validation of a Preoperative Nomogram for Endoscopic Management Decision Making in Upper Urinary Tract Urothelial Carcinoma.

OBJECTIVE: We aimed to develop and validate a preoperative nomogram that predicts low-grade, non-muscle invasive upper urinary tract urothelial carcinoma (LG-NMI UTUC), thereby aiding in the accurate selection of endoscopic management (EM) candidates. METHODS: This was a retrospective study that included 454 patients who underwent radical surgery (Cohort 1 and Cohort 2), and 26 patients who received EM (Cohort 3). Utilizing a multivariate logistic regression model, a nomogram predicting LG-NMI UTUC was developed based on data from Cohort 1. The nomogram's accuracy was compared with conventional European Association of Urology (EAU) and National Comprehensive Cancer Network (NCCN) models. External validation was performed using Cohort 2 data, and the nomogram's prognostic value was evaluated via disease progression metrics in Cohort 3. RESULTS: In Cohort 1, multivariate analyses highlighted the absence of invasive disease on imaging (odds ratio [OR] 7.04; p = 0.011), absence of hydronephrosis (OR 2.06; p = 0.027), papillary architecture (OR 24.9; p < 0.001), and lack of high-grade urine cytology (OR 0.22; p < 0.001) as independent predictive factors for LG-NMI disease. The nomogram outperformed the two conventional models in predictive accuracy (0.869 vs. 0.759-0.821) and exhibited a higher net benefit in decision curve analysis. The model's clinical efficacy was corroborated in Cohort 2. Moreover, the nomogram stratified disease progression-free survival rates in Cohort 3. CONCLUSION: Our nomogram ( https://kmur.shinyapps.io/UTUC_URS/ ) accurately predicts LG-NMI UTUC, thereby identifying suitable candidates for EM. Additionally, the model serves as a useful tool for prognostic stratification in patients undergoing EM.

Hypoxia-inducible factor 2α protein and mRNA expression correlate with histomorphological features in clear cell renal cell carcinoma.

Hypoxia-inducible factor 2α (HIF2α) has been identified as a potential biomarker and novel target for systemic therapy in clear cell renal cell carcinoma (ccRCC). The present study aims to evaluate the association of HIF2α protein and HIF2A mRNA expression with clinicopathological factors and histomorphological features related to vasculature and inflammation of ccRCC using a localized ccRCC cohort (n = 428) and The Cancer Genome Atlas (TCGA)-KIRC cohort (n = 433). HIF2α protein expression was immunohistochemically assessed using tissue microarrays and HIF2A mRNA expression was assessed using the TCGA RNA-sequencing data. Positive HIF2α protein and high HIF2A mRNA expression were observed in 145 (33.9 %) and 142 (32.8 %) patients, respectively. Positive nuclear HIF2α protein expression was significantly associated with the clear histological phenotype and architectural patterns related to rich vascular networks (p < 0.001), and no tumor-associated immune cells status (p < 0.05) in addition to favorable prognostic factors such as lower TNM stage, lower WHO/ISUP grade, or the absence of necrosis (p < 0.001). The HIF2A mRNA expression profile by the TCGA cohort showed similar trends as the HIF2α protein profile. In addition, positive HIF2α protein and high HIF2A mRNA expression were associated with higher recurrence-free survival and overall survival, respectively (both p < 0.001). In conclusion, we comprehensively demonstrated the association of HIF2α profiles with clinicopathological factors and histomorphological features related to vasculature and inflammation at both protein and mRNA levels. Histomorphological features expressing HIF2α may provide information on HIF2α targeted therapeutic response as well as prognosis in ccRCC patients.

Learning from the past and present to change the future: Endoscopic management of upper urinary tract urothelial carcinoma.

Current guidelines recommend endoscopic management (EM) for patients with low-risk upper urinary tract urothelial carcinoma, as well as those with an imperative indication. However, regardless of the tumor risk, radical nephroureterectomy is still mainly performed worldwide despite the benefits of EM, such as renal function maintenance, no hemodialysis requirement, and treatment cost reduction. This might be explained by the association of EM with a high risk of local recurrence and progression. Furthermore, the need for rigorous patient selection and close surveillance following EM may be relevant. Nevertheless, recent developments in diagnostic modalities, pathological evaluation, surgical devices and techniques, and intracavitary regimens have been reported, which may contribute to improved risk stratification and treatments with superior oncological outcomes. In this review, considering recent advances in endourology and oncology, we propose novel treatment strategies for optimal EM.

[Radiofrequency Ablation for Pulmonary Metastasis of Ovarian Cancer Caused Iatrogenic Pneumothorax, Leading to Empyema].

A female patient in her 40s who underwent surgery for recurrent right lung metastasis from resected ovarian cancer was referred to our department because of the right pneumothorax due to radiofrequency ablation for multiple lung metastases. Methicillin-resistant Staphylococcus epidermidis( MRSE) was detected from the tip of the drainage catheter indicated persistent pulmonary fistula with right empyema, and surgical treatment was performed. A white coat of the whole lung surface and air leakage were observed at radiofrequency ablation (RFA) treated lesion and partial resection of the right lung, debridement, and irrigation were performed. A pathological examination revealed residual viable ovarian cancer cells and pleural fistula.

The academic impact and value of an international online surgery lecture series.

Due to the worldwide travel restrictions caused by the 2019 coronavirus disease pandemic, many universities and students lost opportunities to engage in international exchange over the past 2 years. Teleconferencing systems have thus been developed to compensate for severe travel restrictions. Kansai Medical University in Japan and Vilnius University in Lithuania have a collaborative research and academic relationship. The two universities have been conducting an online joint international surgery lecture series for the medical students of both universities. Fifteen lectures were given from October 2021 to May 2022. The lectures focused on gastrointestinal surgery, gastroenterology, radiology, pathology, genetics, laboratory medicine, and organ transplantation. A survey of the attendees indicated that they were generally interested in the content and satisfied with attending this lecture series. Our efforts were successful in providing Japanese and Lithuanian medical students with the opportunity to engage in international exchange through lectures held in each other's countries.

Deep learning-based predictions of clear and eosinophilic phenotypes in clear cell renal cell carcinoma.

We have recently shown that histological phenotypes focusing on clear and eosinophilic cytoplasm in clear cell renal cell carcinoma (ccRCC) correlated with prognosis and the response to angiogenesis inhibition and checkpoint blockade. This study aims to objectively show the diagnostic utility of clear or eosinophilic phenotypes of ccRCC by developing an artificial intelligence (AI) model using the TCGA-ccRCC dataset and to demonstrate if the clear or eosinophilic predicted phenotypes correlate with pathological factors and gene signatures associated with angiogenesis and cancer immunity. Before the development of the AI model, histological evaluation using hematoxylin and eosin whole-slide images of the TCGA-ccRCC cohort (n = 435) was performed by a urologic pathologist. The AI model was developed as follows. First, the highest-grade area on each whole slide image was captured for image processing. Second, the selected regions were cropped into tiles. Third, the AI model was trained using transfer learning on a deep convolutional neural network, and clear or eosinophilic predictions were scaled as AI scores. Next, we verified the AI model using a validation cohort (n = 95). Finally, we evaluated the accuracy of the prognostic predictions of the AI model and revealed that the AI model detected clear and eosinophilic phenotypes with high accuracy. The AI model stratified the patients' outcomes, and the predicted eosinophilic phenotypes correlated with adverse clinicopathological characteristics and high immune-related gene signatures. In conclusion, the AI-based histologic subclassification accurately predicted clear or eosinophilic phenotypes of ccRCC, allowing for consistently reproducible stratification for prognostic and therapeutic stratification.

Prognostic value of immune phenotype and PD-L1 status in recurrent or metastatic renal cell carcinoma: an exploratory analysis of the ARCHERY study.

Studies have reported the relevance of immune phenotype, or presence of cluster of differentiation 8 (CD8)-positive tumour-infiltrating lymphocytes, to the anti-tumour efficacy of checkpoint inhibitors and to prognosis. The multicentre, retrospective ARCHERY study (UMIN000034131) collected tissue samples from Japanese patients with recurrent or metastatic renal cell carcinoma (RCC) who received systemic therapy between 2010 and 2015. In this exploratory analysis, the prognostic impact of immune phenotype and PD-L1 expression (separately and combined) was investigated using 770 surgical specimens and outcomes from patients enrolled in ARCHERY. A key objective was to determine overall survival (OS), defined as time from nephrectomy to death from any cause, by immune and PD-L1 subgroups. The median OS by immune phenotype was 28.8, 57.3, and 63.4 months in patients with inflamed, excluded, and desert tumours, respectively [hazard ratio (95% CI): inflamed 1.78 (1.27-2.49); excluded 1.08 (0.89-1.30); desert as reference]. PD-L1 positivity by SP142 showed a strong association with immune phenotype; 88.1%, 61.9%, and 8.7% of PD-L1-positive patients had inflamed, excluded, and desert phenotypes, respectively. PD-L1 positivity was also associated with worse OS in each phenotype, except for the inflamed phenotype (due to limited sample size in the PD-L1-negative immune inflamed subgroup; n=7). Additionally, the difference in OS by PD-L1 status was larger in the desert versus excluded phenotype [median OS in PD-L1 positive vs negative: 27.1 vs 67.2 months (desert), and 48.2 vs 78.1 months (excluded)]. Results show that PD-L1 expression was highly associated with immune phenotype, but both covariates should be evaluated when determining prognosis.

Prognostic value of PD-L1 expression in recurrent renal cell carcinoma after nephrectomy: a secondary analysis of the ARCHERY study.

BACKGROUND: Nephrectomy is a curative treatment for localized renal cell carcinoma (RCC), but patients with poor prognostic features may experience relapse. Understanding the prognostic impact of programmed death-ligand 1 (PD-L1) expression in patients who underwent nephrectomy for RCC may aid in future development of adjuvant therapy. METHODS: Of 770 surgical specimens collected from Japanese patients enrolled in the ARCHERY study, only samples obtained from patients with recurrent RCC after nephrectomy were examined for this secondary analysis. Patients were categorized into low- and high-risk groups based on clinical stage and Fuhrman grade. Time to recurrence (TTR) and overall survival (OS) were analyzed. RESULTS: Both TTR and OS were shorter in patients with PD-L1-positive than -negative tumors (median TTR 12.1 vs. 21.9 months [HR 1.46, 95% CI 1.17, 1.81]; median OS, 75.8 vs. 97.7 months [HR 1.32, 95% CI 1.00, 1.75]). TTR and OS were shorter in high-risk patients with PD-L1-positive than -negative tumors (median TTR 7.6 vs. 15.3 months [HR 1.49, 95% CI 1.11, 2.00]; median OS, 55.2 vs. 83.5 months [HR 1.53, 95% CI 1.06, 2.21]) but not in low-risk patients. CONCLUSIONS: This ARCHERY secondary analysis suggests that PD-L1 expression may play a role in predicting OS and risk of recurrence in high-risk patients with localized RCC. CLINICAL TRIAL REGISTRATION: UMIN000034131.

Carcinoma of Unknown Original Identified as Renal Cell Carcinoma by 18F-Fluorodeoxyglucose Positron Emission Tomography/Computed Tomography Scan: A Report of Two Cases.

Imaging is useful in identifying the primary site of an unknown primary cancer, and 18F-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) is an excellent imaging modality for identifying the primary lesion. However, a potential limitation is that 18F-FDG is physiologically excreted from the kidneys, thus masking renal lesions. In this report, we describe two cases of cancer of unknown origin that were detected as originating from renal cancer on 18F-FDG PET/CT. Both cases showed abnormal nodular accumulation of 18F-FDG in the kidney, which can be distinguished from the physiological excretion of 18F-FDG in the urinary tract. It is clinically crucial to be able to confirm the possibility of renal cancer, and careful observation of the urinary tract with 18F-FDG PET/CT can be useful.

CD155 immunohistochemical expression in upper tract urothelial carcinoma predicts poor prognosis.

A novel immune checkpoint, CD155/T-cell immunoreceptor with Ig and ITIM domains, has been recognized as a new therapeutic target in addition to conventional immune checkpoints, such as anti-programmed cell death protein 1/programmed cell death ligand 1 (PD-L1), for urothelial carcinoma (UC). Fibroblast growth factor receptor (FGFR) is considered another new therapeutic target for UC. As FGFR3-mutant UC may be associated with decreased T-cell infiltration, FGFR3 inhibition may facilitate lymphocyte invasion into the tumor microenvironment. Although a combined effect of immune checkpoint inhibitors and FGFR inhibition is expected, the combined expression profiles of CD155, PD-L1 and FGFR3 have not been evaluated in upper tract UC (UTUC). The present study aimed to investigate the association between CD155 expression and clinicopathological factors in 208 patients with UTUC undergoing radical nephroureterectomy. Furthermore, the expression profiles of CD155, PD-L1 and FGFR3 were compared. Immunohistochemical analysis was performed using tissue microarray specimens and survival analyses were performed using the Kaplan-Meier method and the Cox proportional hazards model. High immunohistochemical expression of CD155 was observed in 177 patients (85.1%) and it was associated with advanced pathological stage and lymphovascular invasion. The survival rate was lower among patients with tumors exhibiting high CD155 expression than among those with tumors with low CD155 expression. In addition, multivariate survival analysis revealed that high CD155 expression was an independent prognostic factor for recurrence (hazard ratio=7.32, 95% CI=1.01-53.35, P=0.049). FGFR3 and immune checkpoint signaling molecules, such as CD155 and PD-L1, had a weak negative correlation. The present results indicated that the expression of CD155 is a useful marker for predicting the recurrence of UTUC. In addition, the immunohistochemical expression profiles of CD155, PD-L1 and FGFR3 may further the understanding of the role of FGFR-targeted therapies in immunotherapy for UTUC.

Clinical and molecular correlates of response to immune checkpoint blockade in urothelial carcinoma with liver metastasis.

Despite recent advancements in immunotherapy, urothelial carcinoma patients with liver metastasis have a poor response to immune checkpoint inhibitors (ICIs) and short survival durations. Here, we investigated the clinical activity and molecular correlates of resistance to ICI in patients with metastatic urothelial carcinoma (mUC), focusing on liver metastasis. In this study, 755 patients with mUC who received pembrolizumab (JUOG cohort), 144 mUC patients who were treated with atezolizumab (IMvigor210 cohort), and 59 mUC patients who had metastatic samples available were enrolled. The presence of liver metastasis was associated with increased peripheral monocytes and a reduction in lymphocytes when compared with other metastatic sites, and a poor prognosis for ICI therapy. The peripheral monocyte-to-lymphocyte ratio was significantly correlated with the CD163+M2-like tumor-associated macrophage (TAM)/CD8+ tumor-infiltrative lymphocyte (TIL) ratio in the primary and metastatic UC lesions. Exploratory molecular analyses indicated that ICI-resistant status, such as decreased tumor mutation burden, low CD8+ TILs and immune checkpoint signatures, and increased M2-like TAM markers, in primary tumors was correlated with the presence of liver metastasis. In metastatic lesions, the CD163+M2-like TAM/CD8+TIL ratio and expression of cancer-associated fibroblasts induced by the TGFß signaling pathway were higher in the liver versus the lung metastatic tumors. This study indicated that tumor-infiltrating lymphocyte and macrophage status in primary and metastatic lesions, which correlate with peripheral monocyte and lymphocyte status, may predict immunotherapy outcomes in UC patients with liver metastasis.

Sulfatide with ceramide composed of phytosphingosine (t18:0) and 2-hydroxy FAs in renal intercalated cells.

Diverse molecular species of sulfatide with differences in FA lengths, unsaturation degrees, and hydroxylation statuses are expressed in the kidneys. However, the physiological functions of specific sulfatide species in the kidneys are unclear. Here, we evaluated the distribution of specific sulfatide species in the kidneys and their physiological functions. Electron microscopic analysis of kidneys of Cst-deficient mice lacking sulfatide showed vacuolar accumulation in the cytoplasm of intercalated cells in the collecting duct, whereas the proximal and distal tubules were unchanged. Immunohistochemical analysis revealed that vacuolar H+-ATPase-positive vesicles were accumulated in intercalated cells in sulfatide-deficient kidneys. Seventeen sulfatide species were detected in the murine kidney by iMScope MALDI-MS analysis. The distribution of the specific sulfatide species was classified into four patterns. Although most sulfatide species were highly expressed in the outer medullary layer, two unique sulfatide species of m/z 896.6 (predicted ceramide structure: t18:0-C22:0h) and m/z 924.6 (predicted ceramide structure: t18:0-C24:0h) were dispersed along the collecting duct, implying expression in intercalated cells. In addition, the intercalated cell-enriched fraction was purified by fluorescence-activated cell sorting using the anti-vacuolar H+-ATPase subunit 6V0A4, which predominantly contained sulfatide species (m/z 896.6 and 924.6). The Degs2 and Fa2h genes, which are responsible for ceramide hydroxylation, were expressed in the purified intercalated cells. These results suggested that sulfatide molecular species with ceramide composed of phytosphingosine (t18:0) and 2-hydroxy FAs, which were characteristically expressed in intercalated cells, were involved in the excretion of NH3 and protons into the urine.

Useful diagnostic histogenetic features of ectopic odontogenic ghost cell tumours.

BACKGROUND: Ectopic odontogenic tumours are rare and difficult to diagnose. Consequently, they are occasionally misdiagnosed as other tumours and overtreated. Dentinogenic ghost cell tumours (DGCTs) are odontogenic neoplasms characterised by a CTNNB1 mutation, ghost cell appearance, and dentinoid-like calcification. Herein, we present a case of ectopic DGCT on the floor of a patient's mouth, providing reliable clinicopathological and genetic evidence of its odontogenicity for the first time. CASE PRESENTATION: A 72-year-old man presented with painless sublingual swelling. Imaging revealed a multi-lobulated, solid-cystic mass on the floor of his mouth. Cytological evaluation showed folded epithelial clusters composed of basaloid cells, keratinised material, and calcification. Histological analysis revealed a multi-cystic, cribriform to solid nest, with an odontogenic satellate reticulum-like epithelium, including ghost cells and dentinoid matrix deposition. Immunohistochemical analysis found that CK19, CK5/6, bcl-2, and p63 were diffuse positive, ß-catenin was focal positive in the nuclei, and the cells in the dentinoid matrix were positive for DMP1. The CTNTTB1 mutation was detected, leading to the final diagnosis of ectopic DGCT. There was no recurrence during the 6-month follow-up. CONCLUSIONS: Overall, we have presented a comprehensive clinical overview of DGCT and identified its pathological and genetic features. This report will aid in the recognition of this rare disease in the future and help to avoid misdiagnosis and overtreatment.