BACKGROUND:In the tumor microenvironment, immune, stromal and cancer cells interact. They communicate in paracrine and autocrine manners via secreted cytokines, altering anti-tumor immunity. The pattern consisting of the relative secretions of these proteins is referred-to as the "immune secretome". To date, the immune secretome of human cancers remains largely unexplored. Herein, we describe the dominant cytokines released by human tumors. METHODS:We analyzed multiple prospectively collected samples of tumoral and peritumoral tissues. After surgical resection, we promptly titered 40 cytokines released by the samples. RESULTS:Macrophage migration Inhibitory Factor (MIF), Chemokine (C-C motif) ligand 21 (CCL21) and Interleukin 16 (IL-16) were the most strongly detected cytokines in the human tumor secretome. Surprisingly, GM-CSF, IL-10 and IL-2 were undetectable or measured at low levels. Moreover, we observed significant differences in cytokine secretions across different tumor histotypes: while liver metastases, head and neck carcinomas and thyroid tumors secreted large amounts of cytokines (103-105 pg/ gram of tissue across most analytes), the other histotypes secreted at least 10-100 times less of each cytokine per gram of tissue. The liver metastases secreted particularly high amounts of CCL21, IL-16, CXCL10, CCL24 and CCL15, but had low CD45 + cell infiltrates compared to primary tumors. We also found that tumor tissues secreted significantly higher quantities of CXCL1 and CXCL9 than surrounding healthy tissues. CONCLUSIONS:Tumor histology is not associated with a specific secretome, but subgroups of patients share similar secretome profiles independently from their cancer type. This finding supports the development of biology-oriented tumor-agnostic immunotherapy strategies. As the secretome interacts with tumor-infiltrating T-cells, the cytokines identified within it become potential therapeutic targets for personalized cancer immunotherapy.

Background/Objectives: Immunotherapy is an essential part of metastatic bladder cancer treatment. Our main objective was to study the prognostic value of FDG-PET/CT in early assessment of response to Pembrolizumab in metastatic bladder cancers using PERCIST5, imPERCIST5, and PERCIMT criteria. Methods: A total of 42 patients were evaluated with FDG-PET/CT at baseline and after 3–4 cycles of Pembrolizumab. Treatment response was blindly assessed with PERCIST5, imPERCIST5, and PERCIMT. Imaging and clinical data were collected. Progression was defined clinically using oncologist reports. Results: A total of 37 patients were evaluable with the PERCIST5 and imPERCIST5 criteria and included in the analysis. Median disease-specific progression-free survival (PFS) and overall survival (OS) were 152 and 363 days, respectively. All response criteria were significantly associated with PFS. When response was dichotomized in responders versus non-responders all scores were significantly associated with OS. When response was dichotomized in progressors versus non-progressors, only PERCIST5 (hazard ratio (HR) 2.2) and PERCIMT (HR 2.6) were significantly associated with OS, while imPERCIST was not (HR 1.6). Two patients had pseudoprogression (5%), both being adequately classified as non-progressors with PERCIMT criteria. Conclusions: Early response to immunotherapy as assessed with FDG-PET is a strong prognostic factor in bladder cancer patients, especially using the PERCIST5 or PERCIMT criteria. The latter seems clinically useful as it is simple to perform and its specific definition of metabolic progression correctly ruled-out patients with significant clinical benefit of Pembrolizumab in our study.

Background: Advances in chromatography and mass spectrometry have allowed us to develop a novel technique for measuring intraprostatic hormone concentrations directly on prostate needle biopsies, rather than using traditional punch excision. This has significant clinical implications as intraprostatic dihydrotestosterone and testosterone levels could help monitor prostate growth, neoplasia and castration resistance. Methods: Patients undergoing radical cystoprostatectomy for bladder cancer were prospectively included. Each prostate specimen received one 90 mg punch excision and six needle biopsies. Intraprostatic hormones were dosed through gas chromatography-mass spectrometry. Results: We included twenty patients, of which eleven were incidentally diagnosed with prostate cancer; four had ISUP 1 (20%) and seven had ISUP 2 (35%). The prostate biopsy technique was unable to obtain measures for testosterone, Delta-4-androsterone and androstenedione. Tissue concentrations of DHEA, DHT, E1 and E2 can be obtained with no significant difference from the reference established on a punch from a single biopsy core sample. Conclusions: Our study demonstrates that intraprostatic concentrations of DHEA, DHT, E1 and E2 can be measured without significant difference from the reference established on a single punch excision. This finding opens the way to research on the interactions between endocrinology and prostate oncogenesis and particularly on the mechanisms of resistance to hormone therapies in vivo. Level of evidence: 2 (c) 2024 Elsevier Masson SAS. All rights are reserved, including those for text and data mining, AI training, and

Background and objective Failure rates after first-line treatment of localized prostate cancer (PCa) treatment remain high; therefore, it is essential to improve the selection and identification of at-risk patients to reduce mortality. The aim of the ANDROCAN study was to evaluate the biochemical recurrence (BCR) in patients with localized PCa treated by total prostatectomy at 5 yr after surgery, according to their presurgery gonadal status. Methods A prospective cohort study was conducted including 1318 patients undergoing total prostatectomy for localized PCa with a 5-yr postoperative follow-up. Clinical and hormonal data (assays of total testosterone [TT], bioavailable testosterone [BT], dihydrotestosterone, estrone, and estradiol were performed by gas chromatography/mass spectrometry) as well as metabolic syndrome parameters were collected at baseline before surgery. Pathological data (predominant Gleason grade 4 and stage) were collected and cross-referenced centrally. Factors associated with BCR were assessed by a multivariate analysis, and BCR-free survival was assessed by a Kaplan-Meier analysis. Key findings and limitations Among the 1318 patients, 237 had BCR of PCa. Considering demographic characteristics, populations with and without BCR were similar. However, patients with BCR had cancers with a higher Gleason score (p = 0.0001) and higher prostate-specific antigen (PSA) values (p = 0.0005) at baseline. Gleason score, pT >3a, and PSA level at baseline were positively correlated with BCR (p < 0.0001, p < 0.0001, and p = 0.0048, respectively), while BT and TT levels were not associated with BCR. This study includes patients with varying clinical characteristics, such as cancer history and metabolic syndrome, introducing variability that makes it challenging to isolate the specific effects of gonadal status on BCR. Another limitation is the lack of evaluation of long-term BCR beyond 5 yr, potentially overlooking recurrences that occur between 5 and 15 yr after surgery. This could lead to an underestimation of the actual long-term recurrence rates. Conclusions and clinical implications Overall, PSA levels, high Gleason score, and pT >3a are associated with a greater likelihood of disease recurrence following initial treatment and could serve as important prognostic indicators for predicting the risk of BCR. In this prospective study, biochemical hypogonadism was not associated with a higher occurrence of BCR within 5 yr of prostatectomy. The biological gonadal status of preoperative patients could potentially be useful for therapeutic decisions but does not provide an indication for the oncological follow-up. Patient summary Five-year follow up of patients after surgery showed that there is no association between hypogonadism (low levels of total testosterone and bioavailable testosterone) and cancer recurrence. However, cancer recurrence seems to be more associated with aggressiveness of cancer at the time of detection.

The biopsy Gleason score is an important prognostic marker for prostate cancer patients. It is, however, subject to substantial variability among pathologists. Artificial intelligence (AI)-based algorithms employing deep learning have shown their ability to match pathologists’ performance in assigning Gleason scores, with the potential to enhance pathologists’ grading accuracy. The performance of Gleason AI algorithms in research is mostly reported on common benchmark datasets or within public challenges. In contrast, many commercial algorithms are evaluated in clinical studies, for which data is not publicly released. As commercial AI vendors typically do not publish performance on public benchmarks, comparison between research and commercial AI is difficult. The aim of this study is to evaluate and compare the performance of top-ranked public and commercial algorithms using real-world data.We curated a diverse dataset of whole-slide prostate biopsy images through crowdsourcing, containing images with a range of Gleason scores and from diverse sources. Predictions were obtained from five top-ranked public algorithms from the PANDA challenge and from two commercial Gleason grading algorithms. Additionally, ten pathologists evaluated the data set in a reader study.Overall, the pairwise quadratic weighted kappa among pathologists ranged from 0.777 to 0.916. Both public and commercial algorithms showed high agreement with pathologists, with quadratic kappa ranging from 0.617 to 0.900. Commercial algorithms performed on par or outperformed top public algorithms.

Dans le cancer de la prostate localisé, l’impact de l’hypogonadisme biochimique sur l’émergence et la progression du cancer est encore controversée. Notre objectif est de comparer les caractéristiques pathologiques et la récidive biologique (RB) à 5 ans après prostatectomie des patients atteints de cancer de la prostate (CaP) localisé en fonction du statut gonadique évalué par le total (TT) et la biodisponibilité (BT). Une étude de cohorte prospective de 1318 patients (âge 65,0, taille 174 cm, poids 81,5 kg, IMC 26,0 kg/m2, périmètre abdominal 100 cm) atteints de CaP localisé recrutés dans 4 centres urologiques en France, de 6/2013 à 6/2016 ayant tous un suivi de 5 ans postopératoire. Les paramètres du syndrome métabolique (MetS) ont été recueillis. Les dosages de TT, BT, DHT, E1 et E2 ont été réalisés par GC-MS. Un examen croisé centralisé des données pathologiques (grade de Gleason 4 prédominant (PrdGP4), stade) a été effectué. La survie sans RB a été évaluée selon Kaplan-Meier avec comparaisons par test de Log-rank. La cohorte a été divisée en 3 groupes ; le premier (n = 1067 ; 81 %) composé de patients eugonadiques dont la TT et la BT étaient normales (TT ≥ 3 ng/ml et BT ≥ 0,8 ng/ml), le deuxième (n = 251 ; 19 %) de ceux dont la TT et/ou la BT étaient diminuées et le troisième (n = 58 ; 4 %) de ceux dont la TT et la BT étaient diminuées. Les pourcentages de PrdGP4 et de pT ≥ 3 a étaient respectivement de 31 % et 30 % chez les eugonadiques et 41 % et 40 %, et 50 % et 51 % dans les deuxième et troisième groupe (différences significatives). 237 RB ont été observées (fréquence de 17 % chez les eugonadiques contre 21 % chez les hypogonadiques (différence non significative ; Fig. 1) du groupe 2 et 7 % (p = 0,017) chez ceux du groupe 3 (Fig. 1). Cette étude prospective démontre que l’hypogonadisme bioChimique a été associé à des CaP dont les caractéristiques histopathologiques sont plus fréquemment défavorables mais sans survenue significativement supérieure de RB dans les 5 ans après prostatectomie. Par conséquent, le statut gonadique biologique préopératoire des patients est utile pour la décision thérapeutique mais n’indique pas un suivi spécifique sur le plan oncologique.

Supplementary Figure from Escherichia coli–Specific CXCL13-Producing TFH Are Associated with Clinical Efficacy of Neoadjuvant PD-1 Blockade against Muscle-Invasive Bladder Cancer

Background In addition to anti-PD(L)1, anti-CTLA-4 and anti-LAG-3, novel immune checkpoint proteins (ICP)-targeted antibodies have recently failed to demonstrate significant efficacy in clinical trials. In these trials, patients were enrolled without screening for drug target expression. Although these novel ICP-targeted antibodies were expected to stimulate anti-tumor CD8 + T-cells, the rationale for their target expression in human tumors relied on pre-clinical IHC stainings and transcriptomic data, which are poorly sensitive and specific techniques for assessing membrane protein expression on immune cell subsets. Our aim was to describe ICP expression on intratumoral T-cells from primary solid tumors to better design upcoming neoadjuvant cancer immunotherapy trials. Methods We prospectively performed multiparameter flow cytometry and single-cell RNA sequencing (scRNA-Seq) paired with TCR sequencing on freshly resected human primary tumors of various histological types to precisely determine ICP expression levels within T-cell subsets. Results Within a given tumor type, we found high inter-individual variability for tumor infiltrating CD45 + cells and for T-cells subsets. The proportions of CD8 + T-cells (~ 40%), CD4 + FoxP3 - T-cells (~ 40%) and CD4 + FoxP3 + T-cells (~ 10%) were consistent across patients and indications. Intriguingly, both stimulatory (CD25, CD28, 4-1BB, ICOS, OX40) and inhibitory (PD-1, CTLA-4, PD-L1, CD39 and TIGIT) checkpoint proteins were predominantly co-expressed by intratumoral CD4 + FoxP3 + T-cells. ScRNA-Seq paired with TCR sequencing revealed that T-cells with high clonality and high ICP expressions comprised over 80% of FoxP3 + cells among CD4 + T-cells. Unsupervised clustering of flow cytometry and scRNAseq data identified subsets of CD8 + T-cells and of CD4 + FoxP3 - T-cells expressing certain checkpoints, though these expressions were generally lower than in CD4 + FoxP3 + T-cell subsets, both in terms of proportions among total T-cells and ICP expression levels. Conclusions Tumor histology alone does not reveal the complete picture of the tumor immune contexture. In clinical trials, assumptions regarding target expression should rely on more sensitive and specific techniques than conventional IHC or transcriptomics. Flow cytometry and scRNAseq accurately characterize ICP expression within immune cell subsets. Much like in hematology, flow cytometry can better describe the immune contexture of solid tumors, offering the opportunity to guide patient treatment according to drug target expression rather than tumor histological type.

Table S1: Baseline clinical characteristics of the 87 primary clear cell RCC patient selected for multiparametric immunofluorescence in situ analysis Table S2: Baseline clinical characteristics of the 42 primary RCC patient with analysis of fresh tumor TIL Table S3 : List of antibodies used for cytometry and in situ immunofluorescence Table S4: Correlation between the total number (Nb) of CD8+T cells and those expressing Tim-3 and/or PD-1 and the Fuhrman grade and UISS. Table S5 : RCC patients characteristics in the prospective cohorts Table S6 : RCC patients characteristics in the retrospective cohorts

Cytology and cystoscopy, the current gold standard for diagnosing urothelial carcinomas, have limits: cytology has high interobserver variability with moderate or not optimal sensitivity (particularly for low-grade tumors); while cystoscopy is expensive, invasive, and operator dependent. The VISIOCYT1 study assessed the benefit of VisioCyt® for diagnosing urothelial carcinoma. VISIOCYT1 was a French prospective clinical trial conducted in 14 centers. The trial enrolled adults undergoing endoscopy for suspected bladder cancer or to explore the lower urinary tract. Participants were allocated either Group 1: with bladder cancer, i.e., with positive cystoscopy or with negative cystoscopy but positive cytology, or Group 2: without bladder cancer. Before cystoscopy and histopathology, slides were prepared for cytology and the VisioCyt® test from urine samples. The diagnostic performance of VisioCyt® was assessed using sensitivity (primary objective, 70

La cystite à éosinophiles est définie histologiquement par une infiltration de la paroi vésicale par des polynucléaires éosinophiles. C’est une pathologie rare, rentrant dans le spectre des cystites interstitielles/syndrome de vessie douloureuse, et dont les causes sont multiples (parasitaire, médicamenteuse entre autres). Dans un certain nombre de cas, il s’agit de formes idiopathiques pouvant s’intégrer dans le cadre des syndromes hyperéosinophiliques, et dont les caractéristiques sont mal définies dans la littérature. Décrire les caractéristiques cliniques, biologiques, et les réponses au traitement des cystites à éosinophiles idiopathiques (CEI). Ont été inclus, après appel à observations, de manière rétrospective et multicentrique 21 patients identifiés en France avec une CEI définie histologiquement, ainsi que 145 cas de la littérature. Tous les patients ayant une cause définie de cystite à éosinophiles ont été exclus. La CEI est observée aussi bien chez l’adulte que chez l’enfant (respectivement 16 adultes et 5 enfants dans les cas de la série française, 84 adultes et 61 enfants dans la littérature), avec une discrète prédominance masculine (respectivement 62 % et 63 %). L’ensemble des patients étaient symptomatiques correspondant pour la majorité à des symptômes d’irritation vésicale. Une masse vésicale pseudo-tumorale cliniquement palpable était retrouvée chez près d’1/4 des patients. L’incontinence urinaire était présente chez 80 % des enfants (38 % chez l’adulte). Une urétéro-hydronéphrose uni- ou bilatérale compliquait la CEI dans 29 % des cas. Une éosinophilie sanguine était présente chez 60 % des patients, supérieure à 1,5 G/L dans seulement 27 % des cas. Il existait pour 10 % des patients un syndrome hyperéosinophilique avec atteinte digestive associée, mais aucun cas d’atteinte cardiaque ni de syndrome hyperéosinophilique clonal ou lymphoïde n’a été identifié. Environ 15 % des patients ont guéri spontanément, sans aucun traitement. La corticothérapie était le traitement majoritaire (61 %) et induisait une rémission complète ou partielle dans 83 % des cas. Une rechute était observée chez 33 % des patients dans la littérature et 41 % des patients de la série française. Des observations isolées semblent montrer l’intérêt d’un traitement immunosuppresseur (ciclosporine) ou de traitements ciblés (imatinib, benralizumab, mepolizumab) en cas de rechute ou de résistance aux corticoïdes. La CEI idiopathique est une entité histologiquement bien définie, rentrant le plus souvent dans le cadre d’une maladie à éosinophiles mono-organe et justifiant d’une corticothérapie en l’absence de rémission spontanée. Elle doit être différenciée des autres formes de cystites interstitielles/syndrome de vessie douloureuse. Les mécanismes physiopathologiques sous-jacents restent inconnus. Des traitements ciblant l’IL-5 devront être évalués dans les formes chroniques ou à rechutes.

Initial pelvic lymph node (LN) staging is pivotal for treatment planification in patients with muscle-invasive bladder cancer (MIBC), but [18F]FDG PET/CT provides insufficient and variable diagnostic performance. We aimed to develop and validate a machine-learning-based combination of criteria on [18F]FDG PET/CT to accurately identify pelvic LN involvement in bladder cancer patients. Consecutive patients with localized MIBC who performed preoperative [18F]FDG PET/CT between 2010 and 2017 were retrospectively assigned to training (n = 129) and validation (n = 44) sets. The reference standard was the pathological status after extended pelvic LN dissection. In the training set, a random forest algorithm identified the combination of criteria that best predicted LN status. The diagnostic performances (AUC) and interrater agreement of this combination of criteria were compared to a consensus of experts. The overall prevalence of pelvic LN involvement was 24 • The developed machine-learning-based combination of criteria performs as well as experts to detect pelvic LN involvement on [ 18 F]FDG PET/CT in patients with muscle-invasive bladder cancer. • The top 3 features to predict LN involvement were the SUVmax of the most intense LN, the product of diameters of the largest LN, and the product of diameters of the primary bladder tumor.

Patients with high-risk, nonmuscle-invasive bladder cancer (NMIBC) frequently relapse after standard intravesical bacillus Calmette-Guérin (BCG) therapy and may have a dismal outcome. The mechanisms of resistance to such immunotherapy remain poorly understood. Here, using cancer cell lines, freshly resected human bladder tumors, and samples from cohorts of patients with bladder cancer before and after BCG therapy, we demonstrate 2 distinct patterns of immune subversion upon BCG relapse. In the first pattern, intracellular BCG infection of cancer cells induced a posttranscriptional downregulation of HLA-I membrane expression via inhibition of autophagy flux. Patients with HLA-I-deficient cancer cells following BCG therapy had a myeloid immunosuppressive tumor microenvironment (TME) with epithelial-mesenchymal transition (EMT) characteristics and dismal outcomes. Conversely, patients with HLA-I-proficient cancer cells after BCG therapy presented with CD8+ T cell tumor infiltrates, upregulation of inflammatory cytokines, and immune checkpoint-inhibitory molecules. The latter patients had a very favorable outcome. We surmise that HLA-I expression in bladder cancers at relapse following BCG does not result from immunoediting but rather from an immune subversion process directly induced by BCG on cancer cells, which predicts a dismal prognosis. HLA-I scoring of cancer cells by IHC staining can be easily implemented by pathologists in routine practice to stratify future treatment strategies for patients with urothelial cancer.

Abstract Biomarkers guiding the neoadjuvant use of immune-checkpoint blockers (ICB) are needed for patients with localized muscle-invasive bladder cancers (MIBC). Profiling tumor and blood samples, we found that follicular helper CD4+ T cells (TFH) are among the best therapeutic targets of pembrolizumab correlating with progression-free survival. TFH were associated with tumoral CD8 and PD-L1 expression at baseline and the induction of tertiary lymphoid structures after pembrolizumab. Blood central memory TFH accumulated in tumors where they produce CXCL13, a chemokine found in the plasma of responders only. IgG4+CD38+ TFH residing in bladder tissues correlated with clinical benefit. Finally, TFH and IgG directed against urothelium-invasive Escherichia coli dictated clinical responses to pembrolizumab in three independent cohorts. The links between tumor infection and success of ICB immunomodulation should be prospectively assessed at a larger scale. Significance: In patients with bladder cancer treated with neoadjuvant pembrolizumab, E. coli–specific CXCL13 producing TFH and IgG constitute biomarkers that predict clinical benefit. Beyond its role as a biomarker, such immune responses against E. coli might be harnessed for future therapeutic strategies. This article is highlighted in the In This Issue feature, p. 2221

e16558 Background: Voided urinary cytology is a non-invasive test, but it suffers from a lack of sensitivity (Se), particularly in low-grade urothelial lesions, and it remains pathologist-dependent. In order to improve the performance of urinary cytopathology, the VitaDX company (France) developed a medical device which uses whole-slide digitalization and artificial intelligence algorithms to identify tumor cells. The device allows complete analysis of morphological characters of voided urothelial cells, such as the shape, size and color of the nuclei. Methods: VISIOCYT1 is a prospective, multicenter clinical trial involving 319 patients divided into two groups: 1) patients with non-muscle invasive bladder tumors (NMIBC) confirmed by histology, and 2) control patients with negative urinary cytology and cystoscopy. The primary objective of the study was to evaluate the Se of the VisioCyt test. Specificity (Sp) and comparison of Se and Sp of conventional urinary cytology vs. the VisioCyt test were also calculated. Results: A total of 319 patients were included (170 in the NIMBC group vs. 149 controls). Overall Se was 80.9% and 45.9% for VisioCyt test and conventional urinary cytology, respectively (p = .002). Negative cytology being an inclusion criterion, a 100% Sp was attributed to the control group. It was calculated at 61.8% for the VisioCyt test. Concerning grade, the VisioCyt test allowed higher Se to be obtained in the low grade tumor category (66.7% vs. 26.1% for conventional urinary cytology, Mc Nemar test, p < .0001). A higher Se was also observed in high grade tumors: 93.7% vs. 62.8% (p < .0001). Conclusions: The VisioCyt test greatly improves the performance of urinary cytopathology in the diagnosis of urothelial bladder tumors, particularly in low grade, pTa lesions. Its implementation could dramatically reduce the need for cystoscopy in patients followed after conservative treatment of bladder cancer. Clinical trial information: NCT02966691. [Table: see text]

Objective To explore the utility of artificial intelligence (AI) using the VisioCyt® test (VitaDX International, Rennes, France) to improve diagnosis of bladder carcinoma using voided urine cytology. Patients and Methods A national prospective multicentre trial (14 centres) was conducted on 1360 patients, divided in two groups. The first group included bladder carcinoma diagnosis with different histological grades and stages, and the second group included control patients based on negative cystoscopy and cytology results. The first step of this VISIOCYT1 trial focussed on algorithm development and the second step on validating this algorithm. A total of 598 patients were included in this first step, 449 patients with bladder tumours (219 high‐grade and 230 low‐grade) and 149 as negative controls. The VisioCyt test was compared to voided urine cytology performed by experienced uro‐pathologists from each centre. Results Overall sensitivity was highly improved by the VisioCyt test compared to cytology (84.9% vs 43%). For high‐grade tumours the VisioCyt test sensitivity was 92.6% vs 61.1% for the uro‐pathologists. Regarding low‐grade tumours, VisioCyt test sensitivity was 77% vs 26.3% for the uro‐pathologists. Conclusion In comparison to routine cytology, the results of the first phase of the VISIOCYT1 trial show very clear progress in terms of sensitivity, which is particularly visible and interesting for low‐grade tumours. If the validation cohort confirms these results, it could lead to the VisioCyt test being considered as a very useful aid for pathologists. Moreover, as this test is in fact software based on AI, it should become more and more efficient as more data are collected.

477 Background:Plasmacytoid urothelial carcinoma (UC) is a rare pathological variant of UC with low chemotherapeutic sensitivity and dismal outcomes. The molecular and immune profiles of such tumors remain poorly investigated. Herein, we investigated the phenotypical features of a cohort of plasmacytoid UC (n = 32) by comparison to a control group of conventional high-grade UC with matched clinicopathological characteristics (n = 30). Methods: Histopathological analysis included the following antibodies: p63, GATA3, CK5/6, CK20 and HER2. In addition, the density of intra-tumor CD8 + lymphocytes, and PD-L1 expression in tumor (TC) and immune cells (IC) were evaluated. Clinical data were collected. Results: Plasmacytoid UC expressed GATA3 (97% vs 86% p = 0.18), CK20 (59% vs 36% p = 0.08) markers and showed a significantly higher rate of HER2 overexpression (2+ and 3+ score: 25% vs 0%, p < 0.01) compared to controls. A significantly lower expression of CK5/6 (22% vs 56%, p < 0.05) and p63 (41% vs 80%, p < 0.05) was observed in plasmacytoid UC compared to controls. The density of tumor-infiltrating CD8+ cells was similar between plasmacytoid and conventional UC (p = 0.5). PD-L1 expression on IC was similar compared to conventional UC (p = 0.3). Overall survival at 5 years was significantly lower among patients with plasmacytoid UC compared to patients with conventional UC (p = 0.02). Conclusions: Together, our study demonstrated that plasmacytoid UC belong to the luminal subtype and display a rather inflamed microenvironment similar to conventional UC. These data support the inclusion of plasmacytoid variant of UC in clinical trials evaluating immune checkpoint inhibitors monotherapy or combination immunotherapeutic strategies.