Expression of Nectin-4 in Chromophobe Renal Cell Carcinoma in a multicenter cohort - early prognostic and therapeutic considerations.

INTRODUCTION: Nectin-4 is a member of the nectin family and a calcium-independent immunoglobuline-like transmembrane protein that contributes to tumor growth and angiogenesis in malignant tumors. A Nectin-4 directed antibody drug conjugate, Enfortumab vedotin-ejf, has recently been approved for treatment in urothelial cancer and is currently under investigation in other tumor entities such as breast, lung, and prostate cancer. In non-clear cell renal cell carcinoma (RCC) vascular endothelial growth factor (VEGF)-directed tyrosine kinase inhibitors and checkpoint inhibitors are currently treatments of choice. However, due to the rarity of disease treatment recommendations for chromophobe RCC (chRCC) are limited and new therapeutic agents urgently needed. In this study, we investigated the expression and prognostic impact of Nectin-4 in a large cohort of chRCC. METHODS: patients who underwent renal surgery due to chRCC were recruited. Clinical data was retrospectively evaluated. Tumor specimen were analyzed for Nectin-4 expression by immunohistochemistry. RESULTS: 81 chRCC patients were eligible for analysis. In 15 (18.5 %) samples tumors were positive for Nectin-4. No significant associations were found for Nectin-4 expression and clinical attributes in patients with chRCC. Kaplan-Meier analysis disclosed a 5 year- overall survival for Nectin-4-negative and Nectin-4-positive tumors of 91.8% versus 100.0% (p=0.316, log rank). CONCLUSIONS: In chRCC a small subset of tumors expresses Nectin-4 potentially amenable to Nectin-4 directed treatment. Expression of Nectin-4 is not associated with parameters of aggressiveness or survival. Due to the rare incidence of chRCC further studies with larger cohorts are warranted.

Immunohistochemical expression of the hepatocyte growth factor in chromophobe renal cell carcinoma.

BACKGROUND: The prognostic value of Hepatocyte growth factor (HGF) in non-clear cell renal cell carcinoma (RCC) is still unclear. The aim of this study is to evaluate the prognostic impact of HGF expression in a large cohort of chromophobe RCC (chRCC). METHODS: Patients who underwent renal surgery due to chRCC were recruited. Clinical data was retrospectively evaluated. Tumor specimen were analyzed for HGF expression by immunohistochemistry. RESULTS: 81 chRCC patients were eligible for analysis, thereof 37 (45.7%) patients were positive for HGF. No significant associations were found for HGF expression and clinical attributes in patients with chRCC. Kaplan-Meier analysis revealed no differences in 5-year overall survival (OS) for patients with HGF- compared to HGF+ tumors (95.0% versus 90.9%; p = 0.410). CONCLUSIONS: In chRCC HGF expression is not associated with parameters of aggressiveness or survival.

Ultrasound-based "CEUS-Bosniak"classification for cystic renal lesions: an 8-year clinical experience.

PURPOSE: Renal cysts comprise benign and malignant entities. Risk assessment profits from CT/MRI imaging using the Bosniak classification. While Bosniak-IIF, -III, and -IV cover complex cyst variants, Bosniak-IIF and -III stand out due to notorious overestimation. Contrast-enhanced ultrasound (CEUS) is promising to overcome this deficit but warrants standardization. This study addresses the benefits of a combined CEUS and CT/MRI evaluation of renal cysts. The study provides a realistic account of kidney tumor boards' intricacies in trying to validate renal cysts. METHODS: 247 patients were examined over 8 years. CEUS lesions were graded according to CEUS-Bosniak (IIF, III, IV). 55 lesions were resected, CEUS-Bosniak- and CT/MRI-Bosniak-classification were correlated with histopathological diagnosis. Interobserver agreement between the classifications was evaluated statistically. 105 lesions were followed by ultrasound, and change in CEUS-Bosniak-types and lesion size were documented. RESULTS: 146 patients (156 lesions) were included. CEUS classified 67 lesions as CEUS-Bosniak-IIF, 44 as CEUS-Bosniak-III, and 45 as CEUS-Bosniak-IV. Histopathology of 55 resected lesions revealed benign cysts in all CEUS-Bosniak-IIF lesions (2/2), 40% of CEUS-Bosniak-III and 8% of CEUS-Bosniak-IV, whereas malignancy was uncovered in 60% of CEUS-Bosniak-III and 92% of CEUS-Bosniak-IV. Overall, CEUS-Bosniak-types matched CT/MRI-Bosniak types in 58% (fair agreement, κ = 0.28). CEUS-Bosniak resulted in higher stages than CT/MRI-Bosniak (40%). Ultrasound follow-up of 105 lesions detected no relevant differences between CEUS-Bosniak-types concerning cysts size. 99% of lesions showed the same CEUS-Bosniak-type. CONCLUSION: The CEUS-Bosniak classification is an essential tool in clinical practice to differentiate and monitor renal cystic lesions and empowers diagnostic work-up and patient care.

The role of claudin-6 in chromophobe renal cell carcinoma.

BACKGROUND: The prognostic value of Claudin-6 (CLDN6) in non clear cell renal cell carcinoma (RCC) is still unclear. AIM: To evaluate the prognostic impact of CLDN6 expression in a large cohort of chromophobe RCC (chRCC). MATERIAL AND METHODS: Patients who underwent renal surgery due to chRCC were recruited. Clinical data were retrospectively evaluated. Tumor specimens were analyzed for CLDN6 expression by immunohistochemistry. RESULTS: 81 chRCC patients were eligible for analysis, thereof 10 (12.3%) patients were positive for CLDN6. No significant associations were found for CLDN6 expression and clinical attributes in patients with chRCC. Kaplan-Meier analysis revealed no differences in overall survival (OS) for patients with CLDN6⁻ compared to CLDN6⁺ tumors (87.0% versus 62.5%; p=0.174). CONCLUSION: In chRCC CLDN6 expression is not associated with parameters of aggressiveness or survival. Due to the rare incidence of chRCC further studies with larger cohorts are warranted.

Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry Imaging: Diagnostic Pathways and Metabolites for Renal Tumor Entities.

BACKGROUND: Correct tumor subtyping of primary renal tumors is essential for treatment decision in daily routine. Most of the tumors can be classified based on morphology alone. Nevertheless, some diagnoses are difficult, and further investigations are needed for correct tumor subtyping. Besides histochemical investigations, high-mass-resolution matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI) can detect new diagnostic biomarkers and hence improve the diagnostic. PATIENTS AND METHODS: Formalin-fixed paraffin embedded tissue specimens from clear cell renal cell carcinoma (ccRCC, n = 552), papillary renal cell carcinoma (pRCC, n = 122), chromophobe renal cell carcinoma (chRCC, n = 108), and renal oncocytoma (rO, n = 71) were analyzed by high-mass-resolution MALDI fourier-transform ion cyclotron resonance (FT-ICR) MSI. The SPACiAL pipeline was executed for automated co-registration of histological and molecular features. Pathway enrichment and pathway topology analysis were performed to determine significant differences between RCC subtypes. RESULTS: We discriminated the four histological subtypes (ccRCC, pRCC, chRCC, and rO) and established the subtype-specific pathways and metabolic profiles. rO showed an enrichment of pentose phosphate, taurine and hypotaurine, glycerophospholipid, amino sugar and nucleotide sugar, fructose and mannose, glycine, serine, and threonine pathways. ChRCC is defined by enriched pathways including the amino sugar and nucleotide sugar, fructose and mannose, glycerophospholipid, taurine and hypotaurine, glycine, serine, and threonine pathways. Pyrimidine, amino sugar and nucleotide sugar, glycerophospholipids, and glutathione pathways are enriched in ccRCC. Furthermore, we detected enriched phosphatidylinositol and glycerophospholipid pathways in pRCC. CONCLUSION: In summary, we performed a classification system with a mean accuracy in tumor discrimination of 85.13%. Furthermore, we detected tumor-specific biomarkers for the four most common primary renal tumors by MALDI-MSI. This method is a useful tool in differential diagnosis and biomarker detection.

Growth Arrest-Specific 6 in Chromophobe Renal Cell Carcinoma.

BACKGROUND: Overexpression of tumor-associated growth arrest-specific protein 6 (Gas6) is found in many tumor entities. The prognostic value of Gas6 in renal cell carcinoma (RCC), especially in non-clear cell RCC, is still unclear. AIM: The aim of the study was to evaluate the prognostic impact of Gas6 expression in a large cohort of patients with chromophobe RCC (chRCC). MATERIAL AND METHODS: Patients who underwent renal surgery due to chRCC were retrospectively evaluated. Tumor specimens were analyzed for Gas6 expression by immunohistochemistry. RESULTS: Eighty-one chRCC patients were eligible for analysis; of these, 24 (29.6%) patients were positive for Gas6. No significant associations were found for Gas6 expression and clinical attributes in patients with chRCC. The Kaplan-Meier analysis revealed no differences in 5-year overall survival for Gas6- compared to Gas6+ (89.6% vs. 100.0%; p = 0.288) tumors. CONCLUSION: In chRCC, Gas6 expression is not associated with survival and other parameters of aggressiveness. Due to the rare incidence of chRCC, further studies with larger cohorts are warranted.

MALDI Mass Spectrometry Imaging-Prognostic Pathways and Metabolites for Renal Cell Carcinomas.

High mass resolution matrix-assisted laser desorption/ionization (MALDI) mass spectrometry imaging (MSI) is a suitable method for biomarker detection for several tumor entities. Renal cell carcinoma (RCC) is the seventh most common cancer type and accounts for more than 80% of all renal tumors. Prognostic biomarkers for RCC are still missing. Therefore, we analyzed a large, multicenter cohort including the three most common RCC subtypes (clear cell RCC (ccRCC), papillary RCC (pRCC) and chromophobe RCC (chRCC)) by MALDI for prognostic biomarker detection. MALDI-Fourier-transform ion cyclotron resonance (FT-ICR)-MSI analysis was performed for renal carcinoma tissue sections from 782 patients. SPACiAL pipeline was integrated for automated co-registration of histological and molecular features. Kaplan-Meier analyses with overall survival as endpoint were executed to determine the metabolic features associated with clinical outcome. We detected several pathways and metabolites with prognostic power for RCC in general and also for different RCC subtypes.

Trophoblast Cell Surface Antigen 2 (Trop2) in Chromophobe Renal Cell Carcinoma.

BACKGROUND: Overexpression of tumor-associated calcium signal transducer 2 (Trop2) is found in many tumor entities. The prognostic value of Trop2 in renal cell renal carcinoma (RCC), especially in nonclear cell RCC, is still unclear. AIM: The aim of this study was to evaluate the prognostic impact of Trop2 expression in a large cohort of patients with chromophobe (ch)RCC. MATERIALS AND METHODS: Patients who underwent renal surgery due to chRCC were retrospectively evaluated. Tumor specimens were analyzed for Trop2 expression by immunohistochemistry. RESULTS: Eighty-one chRCC patients were eligible for analysis, of these 24 (29.6%) patients were positive for Trop2. No significant associations were found for Trop2 expression and clinical attributes in patients with chRCC. The Kaplan-Meier analysis revealed no differences in 5-year overall survival for Trop2- compared to Trop2+ (89.6% vs. 100.0%; p = 0.288). CONCLUSION: In chRCC, Trop2 expression is not associated with survival and other parameters of aggressiveness. Due to the rare incidence of chRCC, further studies with larger cohorts are warranted.

[Virtual skills-training in urology : Teaching at the Technical University of Munich during the COVID-19-pandemic]. / Virtueller Praktikumstag Urologie : Studentenunterricht an der Technischen Universität München in Zeiten der COVID-19-Pandemie.

BACKGROUND AND INTRODUCTION: The COVID-19 pandemic presents the challenge for medical education to teach practical skills without practical training. To provide an alternative to hands-on training during the COVID-19 lockdown, we created a virtual curriculum to teach practical skills using videos combined with online exams on a virtual e­learning platform. The goal was to convey different theoretical and practical aspects of urology. MATERIALS AND METHODS: The videos were produced by department employees using a predefined concept. The students had access to the virtual curriculum via the university's Moodle e­learning platform. To assess the success of training, participating students had to pass an online exam about the curriculum's contents, followed by an evaluation of the course. RESULTS: A total of 164 participants took part in the virtual curriculum. The overall evaluation and feedback was very positive. The acceptance of the virtual alternative to hands-on teaching was high. DISCUSSION: The virtual curriculum offered a fast and contactless alternative to the regular hands-on teaching.

KLK3 and TMPRSS2 for molecular lymph-node staging in prostate cancer patients undergoing radical prostatectomy.

BACKGROUND: Lymph-node (LN) metastasis in prostate cancer (PC) is a main risk factor for tumor recurrence after radical prostatectomy (RP). Molecular analysis facilitates detection of small-volume LN metastases with higher sensitivity than histopathology. We aimed to prospectively evaluate six candidate gene markers for detection of pelvic LN metastases and to determine their ability to predict biochemical recurrence-free survival (bRFS) in patients treated with RP. METHODS: The expression of kallikrein 2, 3, and 4 (KLK2, KLK3, and KLK4), prostate-specific membrane antigen (PSMA), transmembrane serine protease 2 (TMPRSS2) and transient receptor potential cation channel subfamily M member 8 (TRPM8) was assessed using qPCR. We analyzed LNs from 111 patients (intermediate PC, n = 32 (29%); high-risk PC, n = 79 (71%)) who underwent RP and extended pelvic lymph-node dissection without neoadjuvant treatment. RESULTS: Overall, 2411 LNs were examined by molecular and histopathologic examination. Histopathology detected 69 LN metastases in 28 (25%) patients. KLK2 and KLK3 diagnostically performed best and classified all pN1-patients correctly as molecular node-positive (molN1/pN1). The concordance on LN level was best for KLK3 (96%). KLK2, KLK3, KLK4, PSMA, TMPRSS2, and TRPM8 reclassified 27 (24%), 32 (29%), 29 (26%), 8 (7%), 13 (12%), and 23 (21%) pN0-patients, respectively, as node-positive (pN0/molN1). On multivariable cox regression analysis molecular LN status (molN1 vs. molN0) using KLK3 (HR 4.0, p = 0.04) and TMPRSS2 (HR 5.1, p = 0.02) were independent predictors of bRFS. Median bRFS was shorter in patients with only molecular positive LNs (molN1/pN0) for KLK3 (24 months, p = 0.001) and for TMPRSS2 (12 months, p < 0.001) compared to patients with negative nodes (molN0/pN0) (median bRFS not reached). CONCLUSIONS: For diagnostic purposes, KLK3 showed highest concordance with histopathology for detection of LN metastases in PC patients undergoing RP. For prognostic purposes, KLK3 and TMPRSS2 expression were superior to histopathologic LN status and other transcripts tested for molecular LN status. We suggest a combined KLK3/TMPRSS2 panel as a valuable diagnostic and prognostic tool for molecular LN analysis.

Correction to: Multi-institutional re-evaluation of prognostic factors in chromophobe renal cell carcinoma: proposal of a novel two-tiered grading scheme.

The legends of Figs. 1 and 3 in the published original version of the above article are incorrect.

Molecular lymph node staging for bladder cancer patients undergoing radical cystectomy with pelvic lymph node dissection.

OBJECTIVE: Presence of lymph node (LN) metastasis in bladder cancer (BCa) is a main risk factor for tumor recurrence after radical cystectomy (RC). Molecular analysis facilitates detection of small-volume LN metastases with higher sensitivity than standard histopathology. The aim of the present study was to establish molecular LN analysis in BCa patients undergoing RC with lymph node dissection (LND) and to determine its ability to predict tumor recurrence. PATIENTS AND METHODS: Five transcripts with overexpression in BCa (FXYD3, KRT17, KRT20, SPINK1, UPKII) were evaluated for molecular LN analysis. We included 76 BCa patients from the prospective, randomized surgical phase-III trial (LEA AUO AB 25/02, NCT01215071) investigating extended vs. limited LND at RC. The primary endpoint was recurrence-free survival (RFS). As control, 136 LNs from 45 patients without BCa were analyzed to determine a threshold for pathologic gene expression. RESULTS: About 1,319 LNs were investigated with molecular and histopathologic examination. Histopathology detected 39 LN metastases in 17 (22%) patients. Of the tested genes FXYD3 performed best and classified all pN+-patients correctly as node-positive (pN+/molN+). In addition, FXYD3 reclassified 43 histopathologic negative LNs and 7 (9%) pN0-patients as molecular node-positive (pN0/molN+). Molecular and histopathologic LN status (pN0/molN0 vs. pN0/molN+ vs. pN+/molN+) was significantly associated with locally advanced disease (P = 0.006) and poor RFS (P < 0.001). Median RFS was not reached in LN-negative patients (pN0/molN0), 45 months (95%CI 8-83) in exclusively molecular positive patients (pN0/molN+) and 9 months (95%CI 5-13) in patients with histopathologic and molecular positive LNs (pN+/molN+). CONCLUSIONS: Molecular LN analysis with FXYD3 identified additional LN metastases in histopathologic negative LNs and identified patients with elevated risk of tumor recurrence after RC. Thus, molecular LN analysis improves LN staging and might serve as a tool to guide adjuvant treatment.

Multi-institutional re-evaluation of prognostic factors in chromophobe renal cell carcinoma: proposal of a novel two-tiered grading scheme.

A histological grading system of chromophobe renal cell carcinoma (chRCC) is highly desirable to identify approximately 5-10% of tumors at risk for progression. Validation studies failed to demonstrate a correlation between the four-tiered WHO/ISUP grade and outcome. Previous proposals with three-tiered chromophobe grading systems could not be validated. In this study, the presence of sarcomatoid differentiation, necrosis, and mitosis was analyzed in a Swiss cohort (n = 42), an Italian cohort (n = 103), a German cohort (n = 54), a Japanese cohort (n = 119), and The Cancer Genome Atlas cohort (n = 64). All 3 histological parameters were significantly associated with shorter time to tumor progression and overall survival in univariate analysis. Interobserver variability for identification of these parameters was measured by Krippendorff's alpha coefficient and showed high concordance for the identification of sarcomatoid differentiation and tumor necrosis, but only low to medium concordance for the identification of mitosis. Therefore, we tested a two-tiered tumor grading system (low versus high grade) based only on the presence of sarcomatoid differentiation and/or necrosis finding in the combined cohorts (n = 382). pT stage, patient's age (> 65 vs ≤ 65), lymph node and/or distant metastasis, and the two-tiered grading system (low versus high grade) were significantly associated with overall survival and were independent prognostic parameters in multivariate analysis (Cox proportional hazard). This multi-institutional evaluation of prognostic parameters suggests tumor necrosis and sarcomatoid differentiation as reproducible components of a two-tiered chromophobe tumor grading system.

Treatment of carcinoma in situ of the urinary bladder with an alpha-emitter immunoconjugate targeting the epidermal growth factor receptor: a pilot study.

PURPOSE: Patients with carcinoma in situ (CIS) of the bladder refractory to bacillus Calmette-Guérin (BCG) treatment are usually treated with cystectomy. Therefore, new treatment options with preservation of the urinary bladder are needed. The objective of the study was to investigate the feasibility, safety and efficacy of a novel targeted alpha-emitter immunotherapy for CIS after BCG treatment failure. METHODS: A pilot study was conducted in 12 patients (age range 64-86 years, ten men, two women) with biopsy-proven CIS of the bladder refractory to BCG treatment. The patients were treated intravesically with a single instillation (one patient was treated twice) of the alpha-emitter 213Bi coupled to an anti-EGFR antibody (366-821 MBq). The primary aims of the study were to determine the feasibility of treatment with the 213Bi-immunoconjugate and evaluation of adverse effects. Therapeutic efficacy was monitored by histological mapping of the urinary bladder 8 weeks after treatment and at different time points thereafter. RESULTS: The study proved that intravesical instillation of the 213Bi-immunoconjugate targeting EGFR is feasible. No adverse effects were observed and all blood and urine parameters determined remained in their normal ranges. Therapeutic efficacy was considered satisfactory, in that three of the 12 patients showed no signs of CIS 44, 30 and 3 months after treatment. CONCLUSION: Intravesical instillation of 213Bi-anti-EGFR monoclonal antibody was well tolerated and showed therapeutic efficacy. Repeated instillation and/or instillation of higher activities of the 213Bi-immunoconjugate might lead to better therapeutic outcomes. A phase I clinical trial is planned.

Molecular Lymph Node Status for Prognostic Stratification of Prostate Cancer Patients Undergoing Radical Prostatectomy with Extended Pelvic Lymph Node Dissection.

Purpose: Molecular lymph node (LN) analysis using quantitative polymerase chain reaction (qPCR) detects LN metastases with higher sensitivity than histopathology. However, the prognostic role of molecular LN status in prostate cancer patients treated with radical prostatectomy (RP) and extended pelvic LN dissection (ePLND) is unclear. To investigate the association of molecular compared with histopathologic LN status with biochemical recurrence.Experimental Design: Patients with intermediate and high-risk prostate cancer were prospectively enrolled and underwent RP with ePLND, including the obturator, internal, external, and the common iliac region. LNs ≥3 mm were bisected and examined by standard histopathology and qPCR for Kallikrein3 (KLK3) expression. Biochemical recurrence was defined by confirmed postoperative PSA > 0.2 ng/mL.Results: In 111 patients, 2,411 of 3,173 removed LNs were examined by both methods. Histopathology detected 68 LN metastases in 28 (25%) patients. Molecular analysis confirmed elevated KLK3 expression in 65 histopathologic LN metastases of all 28 pN1 patients (pN1/molN1) and additionally reclassified 224 histopathologic negative LNs and 32 (29%) pN0 patients as LN-positive (pN0/molN1).At a median follow-up of 48 months, 52 (47%) patients developed biochemical recurrence. Median biochemical recurrence-free survival was 9 months [95% confidence interval (CI), 0.0-20.1] in pN1/molN1 patients, 24 months (95% CI, 1.7-46.3) in pN0/molN1 patients and was not reached in pN0/molN0 patients (P < 0.001). On multivariable Cox regression analysis, molecular LN status [HR 4.1 (95% CI, 1.9-8.8), P < 0.001] but not histopathologic LN status [HR 1.5 (95% CI, 0.8-3.0), P = 0.198] was confirmed as independent predictor of biochemical recurrence.Conclusions: Molecular LN analysis identified pN0 patients with a high risk of biochemical recurrence and provided superior prognostic information in comparison with histopathology alone. Clin Cancer Res; 24(10); 2342-9. ©2018 AACR.

Prognostic impact of PD-1 and its ligands in renal cell carcinoma.

Programmed death-1 receptor (PD-1) and programmed death-1 receptor-ligand (PD-L1) have been suggested to play a role as prognostic markers in clear cell renal cell carcinoma (ccRCC). The association between PD-L1 and prognosis seems to be more robust than for PD-1. Further, preliminary analyses suggest that neither PD-1 nor its ligands play a role as prognostic markers in non-clear cell RCC, while the prognostic role of PD-L2 in ccRCC as well as in non-clear cell RCC remains unclear.

PD-L2: A prognostic marker in chromophobe renal cell carcinoma?

In the context of cancer immunotherapy, PD-1 as well as PD-L1 has been widely studied in renal cell carcinoma (RCC). PD-1 and PD-L1 play a significant role as prognostic markers in clear cell renal cell carcinoma. In contrast, little is known about PD-L2 expression patterns in RCC, especially in rarer subtypes. The aim of this study was to evaluate the prevalence, distribution and prognostic impact of PD-L2 expression in chromophobe (ch)RCC. Eighty-one patients who underwent renal surgery due to chRCC were retrospectively evaluated. Tumor specimens were analyzed for PD-L2 expression by immunohistochemistry. Expression data were associated with clinicopathological parameters and overall survival (OS). Twenty-three (28.4%) patients showed a PD-L2 > median (PD-L2 high) staining intensity. No significant association between clinicopathological parameters and PD-L2 expression was identified. A significant difference between 5- and 10-year OS in dependence of PD-L2 expression was found (PD-L2 low 96.4 and 87.7% vs. PD-L2 high 87.1 and 56%; log rank, p = 0.029). However, in multivariate analysis PD-L2 expression failed to be proofed as an independent prognostic factor. In conclusion, to our knowledge this is the first study evaluating the prognostic impact of PD-L2 in a considerably large cohort of chRCC. Our results showed a significant diminished OS in dependence of PD-L2 expression. This implicates that PD-L2 might play a role as prognostic marker in chRCC demanding further evaluation.

c-Met in chromophobe renal cell carcinoma.

c-Met plays a role as a prognostic marker in clear cell renal cell carcinoma. In addition, recently the tyrosine kinase inhibitor cabozantinib targeting c-Met was approved for the treatment of advanced renal cell carcinoma (RCC). In contrast to clear cell RCC, little is known about c-Met expression patterns in rarer RCC subtypes. The aim of this study was to evaluate the prevalence, distribution and prognostic impact of c-Met expression on chromophobe (ch)RCC. Patients who underwent renal surgery due to chRCC were retrospectively evaluated. Tumor specimens were analyzed for c-Met expression by immunohistochemistry. Expression data were associated with clinicopathological parameters including patient survival. Eighty-one chRCC patients were eligible for analysis. Twenty-four (29.6%) patients showed a high c-Met expression (c-Methigh, staining intensity higher than median). Our results showed an association between c-Methigh expression and the existence of lymph node metastasis (p = 0.007). No further significant clinicopathological associations with c-Met were identified, also regarding c-Met expression and overall survival. In conclusion, to our knowledge this is the first study evaluating the prognostic impact of c-Met in a considerably large cohort of chRCC. High c-Met expression is associated with the occurrence of lymph node metastasis. This indicates that c-Met might be implicated into metastatic progression in chRCC.

PD-1/PD-L1 expression in chromophobe renal cell carcinoma: An immunological exception?

Immune checkpoint inhibitors targeting the inhibitory cross talk between tumor and immune cells have been approved for therapy in renal cell carcinoma (RCC). In contrast to clear cell RCC, little is known on PD-1/PD-L1 expression patterns in rarer RCC subtypes. The aim of this study was to evaluate the prevalence, distribution and prognostic impact of PD-1 and PD-L1 expression in chromophobe (ch)RCC. Patients who underwent renal surgery due to chRCC were retrospectively evaluated. Tumor specimen was analyzed for PD-1 and PD-L1 expression by immunohistochemistry. Expression data were correlated with clinic-pathological parameters including patient survival. Eighty-one chRCC patients were eligible for analysis, thereof 25 (30.9 %) and 11 (13.6 %) patients were positive for PD-1+ tumor-infiltrating mononuclear cells (TIMCs) and tumoral PD-L1+ expression, respectively. No significant associations were found for PD-1+ TIMC or tumoral PD-L1+ expression and clinical attributes. In addition, no differences in 5- and 10-year overall survival for PD-1- TIMC compared to PD-1+ TIMC (90.5 and 72.2 vs. 100 and 75 %; p = 0.41) and for PD-L1- tumors compared to PD-L1+ tumors (91.9 and 76.4 vs. 100 and 50 %; p = 0.48) were observed. In conclusion, to our knowledge this is the first study to evaluate the prognostic impact of PD-1 and PD-L1 in chRCC. PD-L1 does seem to be expressed in a minority of all chRCC, likewise only a minority of chRCC was infiltrated by PD-1-positive inflammatory cells. Neither PD-1+ TIMC nor tumoral PD-L1+ expression was associated with parameters of aggressiveness or survival.