Oncologic Outcomes Following Robot-Assisted Radical Prostatectomy for Clinical T3 Prostate Disease.

BACKGROUND: Little is known about oncologic outcomes following robot-assisted-radical-prostatectomy (RALP) for clinical T3 (cT3) prostate cancer. OBJECTIVES: To investigate oncologic outcomes of patients with cT3 prostate cancer treated by RALP. METHODS: Medical records of patients who underwent RALP from 2010 to 2018 were retrieved. cT3 cases were reviewed. Demographic and pre/postoperative pathology data were analyzed. Patients were followed in 3-6 month intervals with repeat PSA analyses. Adjuvant/salvage treatments were monitored. Biochemical recurrence (BCR) meant PSA levels of ≥ 0.2 ng/ml. RESULTS: Seventy-nine patients met inclusion criteria. Median age at surgery was 64 years. Preoperative PSA level was 7.14 ng/dl, median prostate weight was 54 grams, and 23 cases (29.1%) were down-staged to pathological stage T2. Positive surgical margin rate was 42%. Five patients were lost to follow-up. Median follow-up time for the remaining 74 patients was 24 months. Postoperative relapse in PSA levels occurred in 31 patients (42%), and BCR in 28 (38%). Median time to BCR was 9 months. The overall 5-year BCR-free survival rate was 61%. Predicting factors for BCR were age (hazard-ratio [HR] 0.85, 95% confidence interval [95%CI] 0.74-0.97, P = 0.017) and prostate weight (HR 1.04, 95%CI 1.01-1.08, P = 0.021). Twenty-six patients (35%) received adjuvant/salvage treatments. Three patients died from metastatic prostate cancer 31, 52, and 78 months post-surgery. Another patient died 6 months post-surgery of unknown reasons. The 5-year cancer-specific survival rate was 92. CONCLUSIONS: RALP is an oncologic effective procedure for cT3 prostate cancer. Adjuvant/salvage treatment is needed to achieve optimal disease-control.

A Rare Case of Renal Sarcoma Mimicking Metastatic Osteosarcoma.

Pediatric renal sarcomas are exceedingly rare entities that present diagnostic challenges. We report a remarkable case of a 14-month-old female with an 8 cm right renal mass, accompanied by disseminated bone metastases, posing intricate clinical and histopathological dilemmas. Initial suspicion leaned towards clear cell sarcoma of the kidney (CCSK), however, subsequent histological examination post-chemotherapy revealed high-grade osteosarcoma and further differential considerations arose, including primary renal osteosarcoma and osseous osteosarcoma with secondary renal involvement. Despite inconclusive histology, treatment proceeded with the UH1 chemotherapy protocol for CCSK, incorporating high-dose Methotrexate for potential osteosarcoma, and the patient demonstrated a favorable response to therapy.

Robotic partial nephrectomy is associated with a significantly decreased rate of postoperative pseudoaneurysm compared to open and laparoscopic partial nephrectomy.

While partial nephrectomy offers oncologic efficacy and preserves renal function for T1 renal tumors, renal artery pseudoaneurysm (RAP) remains a rare but potentially life-threatening complication. This study compared RAP incidence across robotic-assisted (RAPN), laparoscopic (LPN), and open (OPN) partial nephrectomies in a large tertiary oncological center. This retrospective study analyzed 785 patients undergoing partial nephrectomy between 2012 and 2022 (398 RAPN, 122 LPN, 265 OPN). Data included demographics, tumor size/location, surgical type, clinical presentation, treatment, and post-operative outcomes. The primary outcome was RAP incidence, with secondary outcomes including presentation, treatment efficacy, and renal function. Seventeen patients (2.1%) developed RAP, presenting with massive hematuria (100%), hemorrhagic shock (5.8%), and clot retention (23%). The median onset was 12 days postoperatively. RAP occurred in 4 (1%), 4 (3.3%), and 9 (3.4%) patients following RAPN, LPN, and OPN, respectively (p = 0.04). Only operative length and surgical approach were independently associated with RAP. Selective embolization achieved immediate bleeding control in 94%, with one patient requiring a second embolization. No additional surgery or nephrectomy was needed. Estimated GFR at one year was similar across both groups (p = 0.53). RAPN demonstrated a significantly lower RAP incidence compared to LPN and OPN (p = 0.04). Emergency angiographic embolization proved effective, with no long-term renal function impact. This retrospective study lacked randomization and long-term follow-up. Further research with larger datasets and longer follow-ups is warranted. This study suggests that robotic-assisted partial nephrectomy is associated with a significantly lower risk of RAP compared to traditional approaches. Emergency embolization effectively treats RAP without compromising long-term renal function.

[Congenital orbital teratoma].

Congenital orbital teratoma is a rare benign tumor, composed of all three germ cell layers. The Lesion presents clinically as uniLateral proptosis in the newborn. In order to diagnose the tumor correctly a multidisciplinary approach is needed, including ophthalmologists, neurosurgeons, pediatrics, radiologists, and pathologists to eventually diagnose the lesion. Early detection and treatment is needed in order to prevent mechanical destruction of adjacent tissues, and blindness from mechanical pressure on the optic nerve. Surgical excision is the treatment of choice. We present a case report of a newborn, diagnosed with congenital orbital teratoma, and discuss the clinical and histological characteristics of the tumor.

Diagnosing Oncocytoma by Core Needle Biopsy: A Single-Center Experience.

Background: Oncocytoma is one of the most common benign kidney tumors, accounting for 3-7% of all solid renal masses. Diagnosing oncocytomas using renal biopsy remains a controversy in the uro-pathologic community. With the increasing use of biopsies for assessment of renal lesions, reaching this pathologically benign diagnosis may prevent further surgical measures and have significant clinical benefit. Objective: To demonstrate our center's results using renal biopsy to diagnose oncocytomas and to suggest that this diagnosis can be made with high success rates. Design: , Setting, and Participants. From our center's database, we retrospectively identified and retrieved all cases of oncocytoma diagnosed between the years 2011 and 2020 by renal biopsy. Medical records of those patients were then reviewed to view follow-up meetings and imaging of the lesions biopsied. Outcome Measurements and Statistical Analysis. In 21 biopsies performed on 19 patients, diagnosis was supported by subsequent follow-up averaging at 3.44 years per patient. Results and Limitations. The lesions exhibited benign behavior during follow-up after biopsy, consistent with the diagnosis of oncocytoma. Conclusions: Our study demonstrates that with good patient selection and proficient cooperation between urologists, radiologists and dedicated uro-pathologists, correctly diagnosing oncocytomas using RCB is a viable task. Patient Summary. Oncocytomas are benign lesions of the kidney. In our study, we reviewed all cases of oncocytomas pathologically diagnosed using renal biopsy from our center's database. We found that in subsequent follow-up later to biopsy, the lesions displayed benign behavior consistent with oncocytoma. The use of percutaneous biopsies to reach this diagnosis could save patients more extensive surgeries.

GLI1 Gene Alterations in Neoplasms of the Genitourinary and Gynecologic Tract.

We report 4 neoplasms of the kidney (2 cases) and uterus (2 cases) harboring rearrangements or amplifications of the GLI1 gene, which because of their unusual clinical presentation, morphology, and immunoprofile mimicked other neoplasms, causing significant diagnostic challenge. The neoplasms occurred in 4 female patients ages 33 to 88 years. Histologically they all demonstrated nodular growth, solid architecture, bland epithelioid to ovoid-spindle cells with pale cytoplasm set in a variably myxoid or hyalinized stroma. One uterine tumor also demonstrated a focal round cell pattern, while another demonstrated focal pleomorphism. Unlike most previously reported neoplasms with these genetic abnormalities, the neoplasms in the current series were negative for S100 protein and minimally reactive for actin. All labeled for CD10 and cyclin D1, while 2 labeled for estrogen receptor and BCOR and 1 labeled for desmin, raising consideration of endometrial stromal sarcoma, myxoid leiomyosarcoma, metastatic breast carcinoma, and glomus tumor. One renal neoplasm demonstrated a GLI1-FOXO4 gene fusion and the other harbored a GLI1 gene rearrangement (unknown partner). The 2 uterine neoplasms exhibited GLI1 gene amplifications. GLI1-altered neoplasms (particularly those with GLI1 amplification) show variable morphology and lack a consistent immunophenotype, and thus may trigger diagnostic challenges which can be resolved by molecular testing.

Classic neurothekeoma (nerve sheath myxoma) and cellular neurothekeoma of the oral mucosa: immunohistochemical profiles.

BACKGROUND: Classic neurothekeoma (nerve sheath myxoma) is regarded as being a true benign cutaneous tumor of nerve sheath origin. Cellular neurothekeoma was separated from the classic type by histogenesis, morphology and immunophenotype. Whether cellular neurothekeoma represents a continuum within the spectrum of classic neurothekeoma or is an independent entity is controversial. Only a small number of classic neurothekeomas of the oral mucosa have been reported and there are even fewer publications on cellular neurothekeoma. We analyzed a series of oral neurothekeomas (classic and cellular) with a panel of neural and other mesenchymal markers to enhance their diagnosis and classification. METHODS: One cellular and three classic neurothekeomas were submitted to a panel of immunohistochemical stains with antibodies against S100, S100A6, NSE, NKI/C3, PGP9.5, α-SMA, HHF-35, CD68 and vimentin. Two cases of neurofibroma (plexiform type), representing a true lesion of neural origin, served as control. RESULTS: The cellular neurothekeoma yielded a positive immunoreaction for S100A6 and NKI/C3 and a negative immunoreaction for S-100. The classic neurothekeomas demonstrated a positive reaction for S-100 and S100A6, but a negative one for NKI/C3. Other markers were non-contributory to distinguishing between these types of lesions. CONCLUSIONS: The small number of reported oral neurothekeomas (classic and cellular) could be due, in part, to the lack of recognition of their particular morphologic and immunohistochemical features. Our results indicate that testing for NKI/C3 immunoreactivity may be of value in distinguishing between cellular and classic neurothekeoma.

Penile secondary lesions: a rare entity detected by PET/CT.

While penile metastases are rare, PET/CT has facilitated their detection. We aimed to describe penile secondary lesions (PSL) identified by PET/CT. We reviewed 18F-FDG and Ga68-PSMA PET/CT records performed in a single center during May 2012-March 2020, for PSL. Of 16,774 18F-FDG and 1,963 Ga68-PSMA-PET scans, PSL were found in 24(0.13%) men with a mean age of 74. PSMA detected PSL in 12 with prostate cancer; FDG identified PSL in 4 with lymphoma, 3 with colorectal cancer, 2 with lung cancer, and one each with bladder cancer, pelvic sarcoma, and leukemia. Mean SUVmax of PSL was 7.9 ± 4.2 with focal uptake in 13(54%). Mean lesion size was 16.5 ± 6.8 mm; 8 at the penile root, 4 along the shaft, and 1 at the glans. CT detected loss of the penile texture in 15(63%). PSL were observed only during relapse or follow-up of disseminated disease. Among those with prostate cancer, PSA varied widely. Fifteen (62.5%) died, at a mean 13.3 ± 15.9 months following PSL demonstration, nine had non-prostate malignancies. PET/CT identified and characterized PSL in a fraction of cancer patients, most commonly those with prostate cancer. PSL universally surfaced in advanced disease, and signaled high mortality, especially in non-prostate cancers.

AKT1 pleckstrin homology domain E17K activating mutation in endometrial carcinoma.

OBJECTIVES: The PI3K/AKT pathway is frequently activated in endometrial carcinoma (EC) mainly due to mutations in the PIK3CA and PTEN genes. These events are common and believed to be the key to endometrial carcinogenesis. Recently, a somatic activating mutation in the AKT1 gene (E17K) was identified in several cancer types. In this study we explored the frequency of this AKT1 mutation in endometrial carcinoma. METHODS: Tumor DNA, extracted from 73 EC was analyzed for AKT1 E17K mutation (G49A) using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). In addition, the tumors were screened for coexisting common mutations in PTEN, PIK3CA and KRAS. RESULTS: The AKT1 E17K mutation was detected in 4% of EC. One of the AKT1-mutated tumors showed coexisting PTEN loss-of-function mutation. CONCLUSION: We identified the AKT1 E17K mutation in 4% of endometrial carcinomas. The presence of double AKT1/ PTEN mutants is in accord with the hypothesis that in EC more than one hit is required to completely activate the PI3K pathway. Furthermore, AKT1 mutations were limited to high grade, advanced stage tumors suggesting that this mutation confers a more aggressive tumor behavior.

Endoscopic management of upper tract urothelial carcinoma-tips and tricks.

Ureteroscopic methods have been rapidly evolving in the last several decades. With advances in flexible devices, optics and laser technologies, the endourologic surgeon has now the tools to treat high-volume tumors, in difficult locations, with good oncologic outcome. This makes radical nephroureterectomy unnecessary in some cases. Endoscopy in the setting of UTUC will surely continue to evolve and become applicable to a wider selection of patients. In this review we describe the surgical technique and provide tips and tricks which we use in our practice of endoscopic retrograde treatment of upper-tract urothelial carcinoma.

Uterine leiomyosarcoma: does the primary surgical procedure matter?

BACKGROUND: Uterine leiomyosarcoma (LMS) has a poor prognosis even after early-stage diagnosis. Because there are no accurate diagnostic tools for preoperatively distinguishing LMS from uterine leiomyoma, surgeons might opt for partial surgical procedures such as myomectomy or subtotal hysterectomy. We sought to determine whether a surgical procedure that cuts through the tumor influences prognosis. MATERIALS AND METHODS: Demographic and clinical data of consecutive patients with stage I LMS treated between 1969 and 2005 were reviewed. The study population was divided into group A: patients whose first surgical intervention was total hysterectomy (n = 21); and group B: patients who underwent procedures involving tumor injury, for example, myomectomy, laparoscopic hysterectomy with a morcellator knife, or hysteroscopic myomectomy (n = 16). Survival rates were analyzed and compared. A Cox proportional hazards model was used to assess the association between variables of interest and prognosis. RESULTS: The median age at diagnosis was 50 years (range, 30-74 years). Median follow-up duration was 44 months. The 2 groups did not differ significantly in age at diagnosis, menopausal status, gravidity, parity, postoperative radiotherapy, or time to last follow-up. Kaplan-Meier curves showed significantly better survival rates (P = 0.04) and a significant advantage in recurrence rate (P = 0.03) for group A compared with group B. Survival in group A was 2.8-fold better than that in group B (95% confidence interval, 1.02-7.67). These estimates remained stable after adjustment for age, menopausal status, and radiotherapy. CONCLUSIONS: In patients with stage I LMS, primary surgery involving tumor injury seems to be associated with a worse prognosis than total hysterectomy as a primary intervention.

Promising effect of aromatase inhibitors on recurrent granulosa cell tumors.

Recurring adult-type granulosa cell tumors of the ovary are usually treated by surgical resection followed by chemotherapy or radiation. However, the results of such treatment are disappointing. We describe 4 patients in whom recurrent ovarian granulosa cell tumors were treated with an aromatase inhibitor, with promising results.

Villoglandular papillary adenocarcinoma of the uterine cervix: a diagnostic challenge.

Villoglandular papillary adenocarcinoma (VGA) is a rare subtype of cervical adenocarcinoma. It tends to appear in younger women and its indolent behavior permits fertility-preserving treatments. Pathologically, VGA presents a diagnostic challenge. The aim of our study was to evaluate the reliability of histological assessment for pre-treatment diagnosis of VGA. The data from the outpatient files of 12 patients in whom VGA had been diagnosed were reviewed. Median age at diagnosis was 38.8 years (range 27-65). Final pathology results confirmed VGA in nine patients. Of these, only two had been correctly diagnosed preoperatively, while in three, the initial biopsies were benign or pre-malignant. In four patients, the biopsy results had been interpreted as an invasive malignant tumor necessitating hysterectomy. The final histological report on the remaining three patients was invasive cervical adenocarcinoma. We conclude that pre-treatment diagnosis should not be based solely on a simple punch biopsy because of its low rate of diagnostic accuracy.

Tumor-infiltrating lymphocytes from human prostate tumors reveal anti-tumor reactivity and potential for adoptive cell therapy.

Advanced prostate cancer remains incurable and is the second leading cause of mortality in men. Immunotherapy based on the adoptive transfer of tumor-infiltrating lymphocytes (TIL) has demonstrated promising clinical results in patients with metastatic melanoma and lately also in other solid tumors. However, the ability to obtain TIL from patients with prostate cancer, considered poorly immunogenic, remains unknown. In this study, we investigate the feasibility of isolating and expanding TIL from primary prostate tumors. We collected tumor specimens from eight patients with diagnosed prostate adenocarcinoma undergoing radical prostatectomy and were able to successfully expand multiple autologous TIL cultures from all patients. Twenty-eight prostate-TIL cultures were further expanded using a standard rapid expansion procedure under Good Manufacturing Practice conditions. TIL cultures were phenotypically characterized for T cell subset composition, differentiation status and co-inhibitory/stimulatory markers such as PD-1, TIM-3, LAG-3, and CD28 and were found to have in general similarity to TIL obtained from patients with melanoma and lung carcinoma previously treated at our center. All analyzed TIL cultures were functional as determined by the capability to produce high level of IFNγ upon stimuli. Most importantly, co-culture assays of prostate-TIL with autologous tumors demonstrated anti-tumor reactivity. In conclusion, these findings demonstrate that functional and anti-tumor reactive TIL can be obtained, despite the immunosuppressive microenvironment of the cancer, thus this study supports the development of TIL therapy for prostate cancer patients.

Oncologic Outcomes of Partial Nephrectomy for Stage T3a Renal Cell Cancer.

BACKGROUND: Partial nephrectomy (PN) for clinical stage T3 tumors is controversial. Radical nephrectomy (RN) has been associated with a greater rate of chronic kidney disease, an increased risk of cardiovascular disease, and increased mortality compared with PN. We present our long-term 2-center experience with PN for stage pT3a tumors and compare the oncologic outcomes with those of similar patients treated with RN. MATERIALS AND METHODS: We reviewed the data from all patients who had undergone nephrectomy for renal cell carcinoma from 1987 to 2015 in 2 medical centers. The study included 134 patients with pathologic stage T3a tumors, of whom 48 and 86 underwent PN and RN, respectively. We compared the 2 groups (PN and RN) using univariate and multivariate analyses. RESULTS: The tumors of all patients with pathologic stage T3a who had undergone PN had been pathologically upstaged from clinical stage T1 or T2. Univariate and multivariate analyses revealed tumor size was significantly different statistically between the study groups (median, 7.0 cm in RN group vs. 4.0 cm in PN group; P < .001). Surgery type was not a predictor of local recurrence (P = .978), metastatic progression (P = .972), death from renal cancer (P = .626), or death from all causes (P = .974) at the 5-year follow-up point. CONCLUSION: The results of the present study have shown similar oncologic outcomes between 48 patients with stage pT3a renal cancer who underwent PN and 86 patients who underwent RN. Although PN was not performed on clinical T3a tumors, our findings suggest that PN can also be considered for these tumors and, thus, avoid the long-term complications of RN. However, strict follow-up protocols are mandatory.

Clinicopathologic Features of a Series of Primary Renal CIC-rearranged Sarcomas With Comprehensive Molecular Analysis.

CIC-rearranged sarcomas rarely occur in visceral organs including the kidney. The most common fusion partner with CIC is the DUX4 gene, but variant fusion partners have also been reported. Herein, we describe the clinicopathologic features and comprehensive molecular profiling of 4 cases of primary renal CIC-rearranged sarcomas. All cases occurred in females, age range 13 to 82 years and included 3 resections and 1 needle biopsy specimen. There was a tendency for development of metastatic disease predominantly to the lungs and poor disease outcome despite different treatment strategies. Histologically, variable round cell (20% to 100%), spindle cell (0% to 80%), and rhabdoid morphologies (0% to 20%) were seen. By immunohistochemistry diffuse WT1 nuclear (2 to 3+, ∼90%) labeling was present in 1 case, with cytoplasmic staining in the others (3+, 40% to 75%). CD99 was focally positive in all 4 cases (≤10%); 1 case each was diffusely positive for c-myc (2 to 3+, ∼90%) and ETV4 (3+, ∼90%); 1 case was focally positive for c-myc (2+, ∼5%) and calretinin (2+, ∼5%); and all cases were negative for cytokeratin and NKX2.2. CIC rearrangement by fluorescence in situ hybridization was present in the 3 cases tested. Comprehensive genomic profiling (CGP) of 3 cases revealed a CIC-DUX4 fusion in 2 cases, and 1 CIC-NUTM1 fusion. All 4 CIC-rearranged renal sarcomas had low mutation burden, and except HLA-A and MLL mutations lacked genomic alterations in other oncogenic drivers. Material from the needle biopsy was insufficient for CGP but that case was positive with the DUX4 immunohistochemical stain as were the 2 CIC-DUX4 tumors. In conclusion, CIC-rearranged sarcomas rarely occur in the kidney with a tendency for poor outcome and in this series we illustrate an example with CIC-NUTM1 fusion, an emerging variant, at a visceral site. Testing by fluorescence in situ hybridization or CGP is optimal to avoid missing cases that harbor variant fusion partners.

Viable triplet pregnancy coexisting with a complete molar pregnancy.

This case is extraordinary because it was never before described in English literature. The case describes a long-standing debate about the safety of carrying this pregnancy to term. Some authors are for and some are against. The risks and benefits should be thoroughly reviewed before a decision is made.

The relative contribution of urine extravasation to elevate plasma creatinine levels in acute unilateral ureteral obstruction.

INTRODUCTION: Rising levels of plasma creatinine in the setting of acute unilateral ureteral obstruction (AUUO) often reflects acute renal failure, mandating kidney drainage. We hypothesize that re-absorption of peri-renal urine extravasation (PUE), a common result of UUO, contributes significantly to the elevation in plasma creatinine, rendering the latter an inaccurate benchmark for renal function. We explored this hypothesis in a rat model of AUUO and PUE. METHODS: In total, 20 rats were equally divided into 4 groups. Groups 1 and 2 underwent unilateral ligation of the ureter with infiltration of rat's urine (index group) or saline (control) into the peri-renal space. Two additional control groups underwent peri-renal injection of either urine or saline without AUUO. Plasma creatinine levels were determined immediately prior to the procedure (T0), and hourly for 3 hours (T1, T2 and T3). Renal histology was investigated after 3 hours. RESULTS: Rats in the index group had a significantly greater increase in plasma creatinine levels over 3 hours compared to all other groups (p < 0.05). At T3, average plasma creatinine levels for the index group increased by 96% (0.49 ± 0.18 mg/dL) compared to 46% (0.23 ± 0.06 mg/dL increase) in the AUUO and saline group, and less than 15% rise in both the non-obstructed control groups. Our study limitations includes lack of spontaneous PUE and intraperitoneal surgical approach. CONCLUSIONS: Absorption of peri-renal urine in the presence of AUUO is a significant contributor to rising plasma creatinine levels, beyond those attributable to the obstruction alone, and may overestimate the extent of the true renal functional impairment.

Correlation between BRCA1 expression and clinicopathological factors including brain metastases in patients with non-small-cell lung cancer.

BACKGROUND: Previously identified as a breast and ovarian cancer susceptibility gene, BRCA1 has gained major scientific interest as a potential prognostic and/or predictive marker for various tumors, including non-small-cell lung cancer (NSCLC), the leading cause of cancer related mortality worldwide. BRCA1 plays a central role in DNA damage response (DDR. It undergoes phosphorylation by various DDR kinases at different serine residues, of which ser1524 is known to be specifically phosphorylated by ATM in response to genotoxic stress. METHODS: We performed BRCA1 immunohistochemistry on several tissue microarrays (TMAs) of 113 early (I, II stage) and advanced (III, IV stage) NSCLCs, using MS110 antibody against the BRCA1 N-terminal and S1524 antibody against the phosphorylated form of BRCA1 protein at ser1524 (Abcam). Patients with III and IV stage disease were treated by adjuvant cisplatin-based chemotherapy. Staining results were correlated with overall survival (OS), disease free survival (DFS) and with the occurrence of brain metastases. RESULTS: BRCA1 S1524 nuclear positivity was significantly correlated with longer OS and DFS in stage I and II patients (P<0.05), while OS and DFS were shorter in S1524 positive stage III and IV patients (P<0.05). No significant correlation was found with brain metastases. CONCLUSION: The results show that BRCA1 phosphorylaton, at least in ser1524, differentiates the fate of early and advanced NSCLC as well as response to chemotherapy, but the underlying mechanisms are not completely understood. Detection of phosphorylated forms of BRCA1 might serve as a useful prognostic and predictive marker for patients with NSCLC.

Development and validation of a microRNA-based diagnostic assay for classification of renal cell carcinomas.

Renal cancers account for more than 3% of adult malignancies and cause more than 13,000 deaths per year in the US alone. The four most common types of kidney tumors include the malignant renal cell carcinomas; clear cell, papillary, chromophobe and the benign oncocytoma. These histological subtypes vary in their clinical course and prognosis, and different clinical strategies have been developed for their management. In some kidney tumor cases it can be very difficult for the pathologist to distinguish between tumor types on the basis of morphology and immunohistochemistry (IHC). In this publication we present the development and validation of a microRNA-based assay for classifying primary kidney tumors. The assay, which classifies the four main kidney tumor types, was developed based on the expression of a set of 24 microRNAs. A validation set of 201 independent samples was classified using the assay and analyzed blindly. The assay produced results for 92% of the samples with an accuracy of 95%.