Aims: Anti‐claudin‐18.2 (CLDN18.2) therapy was recently approved for the treatment of gastric or gastro‐oesophageal junction adenocarcinoma. The aim of the present study was to investigate the expression of CLDN18.2 in cholangiocarcinoma (CCA) to determine whether there is a subgroup of patients who might also benefit from anti‐CLDN18.2 therapy.Methods and results: A tissue microarray (TMA) cohort of all CCA patients who underwent surgical resection with curative intent between August 2005 and December 2021 at University Hospital Frankfurt were immunohistochemically evaluated using the VENTANA^® CLDN18 (43‐14A) antibody. Tumour positivity for CLDN18.2 was determined as follows: ≥ 75% of tumour cells with moderate‐to‐strong CLDN18 membranous staining. In total, 160 patients with surgically resected CCA were suitable for immunohistochemistry (IHC) analysis. Of the patients, 13.1% (n = 21) showed moderate to strong membranous staining of VENTANA^® CLDN18 antibody, while 86.9% (n = 139) were negative. Subtype analysis revealed strong differences in CLDN18 expression. Positive staining of CLDN18 could be observed in 26.5% (n = nine of 34) and 7.4% (n = seven of 95) of the perihilar (pCCA) and intrahepatic (iCCA) subgroup, respectively. CCA patients with CLDN18 expression had a more frequently intraoperative finding of distant metastasis (P = 0.002), lymph node metastasis (P = 0.008) and positive perineural invasion (Pn1) status (P = 0.022).Conclusions: The present study suggests that a subset of patients with CCA exhibited a marked expression of CLDN18.2. These findings underline the need to perform a clinical study evaluating the efficacy of anti‐CLDN18.2 therapy in patients suffering from CCA.

Aims: The histological subtype of intrahepatic cholangiocarcinoma (iCCA) is associated with different mutational characteristics that impact clinical management. So far, data are lacking on the presence of small duct iCCA (SD‐iCCA) and large duct iCCA (LD‐iCCA) in a single patient. The aim of the current study was to determine the presence and degree of intratumoural heterogeneity of SD‐ and LD‐iCCA features in different tumour regions.Methods and results: All patients treated with surgically resected iCCA at Frankfurt University Hospital between December 2005 and March 2023 were retrospectively analysed. Histomorphological features of SD‐ and LD‐iCCA were evaluated by an expert hepatobiliary pathologist. Tissue samples suspicious for subtype heterogeneity were further investigated. Immunohistochemistry for N‐cadherin, S100P, MUC5AC, MUC6, TFF1 and AGR2 and mutational profiling with the Illumina TruSight Oncology 500 (TSO500) assay were performed separately for the SD‐ and LD‐iCCA regions. Of 129 patients with surgically resected iCCA, features of either SD‐ or LD‐iCCA were present in 67.4% (n = 87) and 24.8% of the patients (n = 32), respectively; 7.8% (n = 10) had histomorphological features of both SD‐ and LD‐iCCA, seven patients (5.4%) of which had sufficient formalin‐fixed, paraffin‐embedded tissue for further analysis. Heterogeneity of both subtypes could be confirmed with immunohistochemistry. In five of seven (71.4%) patients, molecular profiling revealed intratumoural differences in genetic alterations between the SD‐ and LD‐iCCA region. In one patient, a BRAF mutation (p.V600E) was found in the SD‐iCCA but not in the LD‐iCCA region of the tumour.Conclusions: A marked portion of patients with iCCA exhibits both SD‐ and LD‐iCCA in different tumour regions. In case of the presence of histopathological heterogeneity, mutational profiling should be considered to avoid missing therapeutically relevant genetic alterations.

MUC16/CA125 is associated with cancer proliferation in several tumor entities. The data on MUC16 expression in cholangiocarcinoma (CCA) tissue are very limited. The aim of this study was to assess the MUC16 status and its impact on survival in CCA patients. All the patients with surgically resected CCA that were diagnosed between August 2005 and December 2021 at the University Hospital Frankfurt were retrospectively analyzed. A 7-Mucin biomarker panel was assessed by immunohistochemistry. For overall survival (OS), Kaplan–Meier curves and Cox-regression analyses were performed. Randomly selected intrahepatic cholangiocarcinoma (iCCA) were further processed for differential expression profiling. A total of 168 patients with CCA were classified as MUC16 (−) (66%, n = 111) and MUC16 (+) (34%, n = 57). Subgroup analyses revealed a median OS of 56.1 months (95% CI = 42.4–69.9 months) and 27.4 months (95% CI = 15.8–39.1 months) for MUC16 (−) and MUC16 (+), respectively (p < 0.001). In multivariate analysis, MUC16 (+) (HR = 1.6, 95% CI = 1–2.6, p = 0.032) was an independent risk factor for poor prognosis. Prominently deregulated pathways have been identified following MUC16 expression, overrepresented in cell cycle and immune system exhaustion processes. These findings suggest including MUC16 in clinical routine diagnostics as well as studying its molecular pathways to identify further mechanistic key players.

Distinct immune patterns of hepatocellular carcinoma (HCC) may have prognostic implications in the response to transarterial chemoembolization (TACE). Thus, we aimed to exploratively analyze tumor tissue of HCC patients who do or do not respond to TACE, and to identify novel prognostic biomarkers predictive of response to TACE. We retrospectively included 15 HCC patients who had three consecutive TACE between January 2019 and November 2019. Eight patients had a response while seven patients had no response to TACE. All patients had measurable disease according to mRECIST. Corresponding tumor tissue samples were processed for differential expression profiling using NanoString nCounter^® PanCancer immune profiling panel. Immune-related pathways were broadly upregulated in TACE responders. The top differentially regulated genes were the upregulated CXCL1 (log2fc 4.98, Benjamini–Hochberg (BH)-p < 0.001), CXCL6 (log2fc 4.43, BH-p = 0.016) and the downregulated MME (log2fc −4.33, BH-p 0.001). CD8/T-regs was highly increased in responders, whereas the relative number of T-regs to tumor-infiltrating lymphocytes (TIL) was highly decreased. We preliminary identified CXCL1 and CXCL6 as candidate genes that might have the potential to serve as therapeutically relevant biomarkers in HCC patients. This might pave the way to improve patient selection for TACE in HCC patients beyond expert consensus.