Transrectal Ultrasound MRI-Fusion Biopsy of Perirectal Mass.

This case report describes the novel use of ultrasound-guided MRI-fusion biopsy to sample an extraluminal perirectal mass. This is a 64-year-old man with a history of pT3N2b mucinous adenocarcinoma of the right colon with metastatic disease to the mesocolic lymph nodes. Two years after initial resection he was found on restaging CT to have a mass measuring ∼4.0 × 4.8 cm superior to the seminal vesicles. Fluorodeoxyglucose (FDG)-positron emission tomography (PET) showed a moderately FDG avid soft tissue mass interposed between the prostate and the rectum. Multiparametric MRI revealed a 6.2 × 4.6 × 2.8 cm heterogeneous lobulated T2 hyperintense mass with enhancement just superior to the seminal vesicles. This mass was unable to be viewed using sigmoidoscopy. Using UroNAV technology, we were able to biopsy the mass in the clinic setting. Biopsy was confirmed as recurrent mucinous adenocarcinoma.

Salvage Cryoablation for Radiorecurrent Prostate Cancer: Initial Experience at a Regional Health Care System.

CONTEXT: Local recurrence after radiotherapy for prostate cancer remains challenging to treat effectively. Although oncologic control is highest with salvage prostatectomy, the procedure is associated with substantial morbidity. OBJECTIVE: To identify factors associated with successful salvage cryoablation for radiorecurrent prostate cancer. DESIGN: We retrospectively reviewed the medical records of patients who underwent salvage cryoablation at our institution between 2005 and 2015. All patients had biopsy-proven local recurrence after radiotherapy. Patients with seminal vesicle invasion or metastases were excluded. Complete follow-up was obtained for all patients. MAIN OUTCOME MEASURES: Primary study endpoint was biochemical progression-free survival based on the Phoenix criteria. RESULTS: Seventy-five patients underwent salvage cryotherapy. Mean patient age was 69.3 years. The overall biochemical salvage rate was 50.7% at a median follow-up of 3.9 years. The following factors were independently associated with successful cryotherapy: Precryotherapy Gleason score of 3 + 3 or 3 + 4, low precryotherapy prostate-specific antigen (PSA), low precryotherapy PSA density, longer time to PSA nadir after radiotherapy, and low postcryotherapy PSA nadir. A postcryotherapy PSA nadir of 0.5 ng/mL or less was associated with a biochemical progression-free survival of 79.7% at 3 years and 64.7% at 5 years, whereas a postcryotherapy PSA nadir above 0.5 was associated with a biochemical progression-free survival of 5.6% at 3 years and 0% at 5 years (p < 0.0001). CONCLUSION: Approximately 50% of the patients achieved biochemical salvage with cryoablation at 5 years. Nadir PSA after salvage was the strongest predictor of biochemical progression-free survival in our cohort.

Radical Prostatectomy and Pelvic Lymph Node Dissection in Kaiser Permanente Southern California: 15-Year Experience.

INTRODUCTION: Radical prostatectomy (RP) with pelvic lymph node dissection (PLND) is the standard treatment of high-risk prostate cancer. High-risk patients and those with lymph node metastasis (LNM) require further treatment. We review outcomes of RP+PLND in Kaiser Permanente Southern California (KPSC). METHODS: Patients who underwent RP+PLND in KPSC from January 1, 2001, to July 1, 2015 were included. Patient charts were retrospectively reviewed for demographic information and clinicopathologic data which were used to calculate positive surgical margin rate, LNM, adjuvant treatment, 5-year biochemical recurrence, and overall survival. Univariate and multivariate logistic regression analyses were used to identify factors associated with margin positivity. RESULTS: Patients (N = 1829) underwent RP+PLND (241 high-risk, 943 intermediate-risk, 645 low-risk). Positive margin rates were 17.8%, 14.8%, and 11.9% in the high, intermediate- and low-risk groups. Biochemical recurrence rates were 22% in high-risk and 12.1% in the low-risk category. Androgen deprivation use was 4.1% in the high-risk group and 0.9% in the low-risk group. Five-year overall survival was 92.5% in lymph node-positive patients and 94.9% in lymph node-negative patients (p = 0.8). On multivariate analysis, age (odds ratio [OR] = 1.02, p = 0.02), prebiopsy prostate-specific antigen (OR = 1.02, p < 0.001), and clinical T stage (OR = 1.49, p = 0.01) were associated with margin positivity. CONCLUSION: In KPSC, RP+PLND was performed in patients with low-, intermediate-, and high-risk prostate cancer. Age, prebiopsy prostate-specific antigen, and clinical stage were associated with positive surgical margins in patients with LNM. Recipients of RP+PLND with LNM and positive surgical margins required adjuvant treatment.

Robot-Assisted Excision of a Urachal Cyst Causing Dyspareunia and Dysorgasmia: Report of a Case.

BACKGROUND: Urachal remnants are a group of rare anatomical anomalies that include cysts, diverticula, and tumors. We present a case of a young female patient with dyspareunia and dysorgasmia related to a urachal cyst. CASE: A patient with unique presentation of urachal cyst treated robotically. Patient had complete resolution of symptoms postoperatively. CONCLUSION: Robot-assisted excision of the urachal remnant provided durable symptom relief.

Tumors of the Anterior Prostate: Implications for Diagnosis and Treatment.

Tumors of the anterior prostate (ie, the portion of the prostate anterior to the urethra) account for approximately 20% of all prostate cancers. Although anterior prostate cancers frequently occur, they have historically been underdetected because of infrequent sampling. Recent advances in multiparametric magnetic resonance imaging and improved biopsy schemes have significantly increased our diagnostic accuracy for detecting anterior tumors. Herein, we review these developments and highlight key aspects of the diagnosis and management of anterior prostate cancers.

Novel ureteroscopic technique for treatment of prolonged caliceal leak after partial nephrectomy.

INTRODUCTION AND OBJECTIVES: Caliceal leak after partial nephrectomy (PN) typically resolves with conservative management. However, persistent fistulae pose a formidable challenge that may require additional therapeutic actions. METHODS: We describe a case of a patient with a solitary kidney who suffered a persistent urine leak following PN. A novel retrograde ureteroscopic approach was taken that utilized the combined techniques of caliceal fulguration and fibrin glue injection. RESULTS: Imaging demonstrated resolution of the caliceal fistula at 13 months postoperatively. CONCLUSIONS: Persistent urine leak after PN remains a burdensome complication that often requires creative steps to resolve. Our case presents a solution using a novel ureteroscopic technique.

Impact of surgical case order on perioperative outcomes for robotic-assisted radical prostatectomy.

OBJECTIVES: Since its introduction, there have been many refinements in the technique and implementation of robotic-assisted radical prostatectomy (RARP). However, it is unclear whether operative outcomes are influenced by surgical case order. We evaluated the effect of case order on perioperative outcomes for RARP within a large health maintenance organization. MATERIALS AND METHODS: We conducted a retrospective review of RARP cases performed at our institution from September 2008 to December 2010 using a single robotic platform. Case order was determined from surgical schedules each day and surgeries were grouped into 1(st), 2(nd) and 3(rd) round cases. Fourth round cases (n = 1) were excluded from analysis. We compared clinicopathological variables including operative time, estimated blood loss (EBL), surgical margin rates and complication rates between groups. RESULTS: Of the 1018 RARP cases in this cohort, 476 (47%) were performed as 1(st) round cases, 398 (39%) 2(nd) round cases and 144 (14%) 3(rd) round cases by a total of 18 surgeons. Mean operative time was shorter as cases were performed later in the day (213 min vs. 209 min vs. 180 min, P < 0.0001) and similarly, EBL also decreased with surgical order (136 mL vs. 134 mL vs. 103 mL, P = 0.01). Transfusion rates, surgical margin rates and complication rates did not significantly differ between groups. Patients undergoing RARP later in the day were much more likely to have a hospital stay of 2 or more days than earlier cases (10% vs. 11% vs. 32%, P = 0.01). CONCLUSIONS: Surgical case order may influence perioperative outcomes for RARP with decreased operative times and increased length of hospital stay associated with later cases. These findings indicate that select perioperative factors may improve with ascending case order as the surgical team "warms up" during the day. In addition, 3(rd) round cases can increase hospital costs associated with increased lengths of hospital stay. Knowledge of these differences may assist in surgical planning to improve outcomes and limit costs.

The role of magnetic resonance imaging in delineating clinically significant prostate cancer.

OBJECTIVE: To determine whether multiparametric magnetic resonance imaging might improve the identification of patients with higher risk disease at diagnosis and thereby reduce the incidence of undergrading or understaging. METHODS: We retrospectively reviewed the clinical records of 115 patients who underwent multiparametric magnetic resonance imaging before radical prostatectomy. We used Epstein's criteria of insignificant disease with and without a magnetic resonance imaging (MRI) parameter (apparent diffusion coefficient) to calculate sensitivity, specificity, as well as negative and positive predictive values [NPV and PPV] across varying definitions of clinically significant cancer based on Gleason grade and tumor volume (0.2 mL, 0.5 mL, and 1.3 mL) on whole-mount prostate specimens. Logistic regression analysis was performed to determine the incremental benefit of MRI in delineating significant cancer. RESULTS: The majority had a prostate-specific antigen from 4.1-10.0 (67%), normal rectal examinations (90%), biopsy Gleason score ≤ 6 (68%), and ≤ 2 cores positive (55%). Of the 58 patients pathologically staged with Gleason 7 or pT3 disease at prostatectomy, Epstein's criteria alone missed 12 patients (sensitivity of 79% and NPV of 68%). Addition of apparent diffusion coefficient improved the sensitivity and NPV for predicting significant disease at prostatectomy to 93% and 84%, respectively. MRI improved detection of large Gleason 6 (≥ 1.3 mL, P = .006) or Gleason ≥ 7 lesions of any size (P <.001). CONCLUSION: Integration of MRI with existing clinical staging criteria helps identify patients with significant cancer. Clinicians should consider utilizing MRI in the decision-making process.

Impact of trainee involvement with robotic-assisted radical prostatectomy.

Robotic-assisted surgery has been rapidly adopted within urology practice. As a result, academic centers are challenged with the burden of how to effectively train residents and fellows to perform robotic-assisted surgery without compromising outcomes. We evaluated the perioperative outcomes of trainee involvement with robotic-assisted radical prostatectomy (RARP) within our healthcare organization. We retrospectively reviewed RARP cases performed at our institution between September 2008 and December 2010 using a single da Vinci robotic platform. Trainees consisted of urology residents and fellows who operated with staff surgeons on select operating days, whereas two staff surgeon teams performed RARP on alternate days. We compared clinicopathologic variables including operating time, estimated blood loss, surgical margin rates, and complication rates between the trainee and staff-only surgeon groups. Overall, 1,019 RARP surgeries were performed within the study period and trainees participated in 162 cases (16 %). Clinical characteristics were similar between men undergoing surgery with a trainee and those without. Positive surgical margin rates were lower for patients with pT2 disease for cases with trainee involvement (11 vs. 19 %, p = 0.02), although overall margin rates and margin rates for patients with pT3 disease were similar between the groups (p = 0.34). Surgical cases involving trainees were longer (241 vs. 200 min, p < 0.001) and resulted in higher estimated blood loss (190 vs. 120 mL, p < 0.001) than the two staff surgeon cases. However, transfusion rates as well as intraoperative and postoperative complication rates did not differ significantly between groups. In conclusion, surgical margin rates were lower in teaching cases for patients with pT2 disease. Importantly, trainee involvement in RARP is safe, with similar perioperative outcomes to staff-only surgical cases. This information may be useful for training and surgical planning.

Fine-tuning robot-assisted radical prostatectomy planning with MRI.

OBJECTIVES: Robot-assisted radical prostatectomy (RARP) has now become the most common surgical treatment option for prostate cancer (CaP). Clinicopathologic data (i.e., biopsy, digital rectal exam, prostate specific antigen level) and patient-specific factors (e.g., age, erectile function, co-morbidities) are the primary sources of information that urologists use for counseling and treatment decision making. Magnetic resonance imaging (MRI) has evolved along a similar temporal arc to RARP, with increased utilization and precision over the past decade. MRI prior to RARP provides multifaceted adjunctive information, including enhancement of locoregional staging, delineation of spatial anatomic information, and identification of aberrant anatomy, all of which aid in patient treatment counseling and operative planning. This article is designed for urologic surgeons who perform RARP, with the aim of providing a review of prostate MRI imaging and highlighting findings which may specifically alter the operation. METHODS AND MATERIALS: A review of the literature was performed, focusing on the most recent publications. RESULTS: MRI imaging of the prostate has become increasing accurate for the identification, localization, and characterization of CaP lesions. In addition to tumor-specific information, a number of intra- and extra-prostatic findings are consistently identified on MRI which may impact RARP. CONCLUSIONS: MRI provides important information which may alter RARP.

Diffusion tensor magnetic resonance tractography of the prostate: feasibility for mapping periprostatic fibers.

OBJECTIVE: To evaluate the feasibility of diffusion tensor imaging (DTI) tractography of the prostate for mapping of periprostatic neurovascular anatomy. METHODS: Eight men with prostate cancer scheduled to undergo nerve-sparing robot-assisted radical prostatectomy (RARP) underwent endorectal multiparametric magnetic resonance imaging (MRI) of the prostate with DTI. Tract mapping was accomplished by positioning spherical regions of interest contiguously along the prostatic capsule at the prostatic apex, midgland, and base. RESULTS: DTI tractography of the prostate effectively visualized periprostatic fiber tract anatomy. There was no significant correlation between total tract number and prostate size, however (Spearman's coefficient = 0.33, P = .42). Variation in tract distribution existed. The total fiber mass was highest in the lower prostate hemisphere at the base of the prostate (mean = 36.9 vs 21.1, P = .0004) and in the upper hemisphere at the apex (mean = 41.6 vs 57.9, P = .006). CONCLUSION: DTI tractography successfully visualized fiber tracts around the prostate. Gold standard anatomic correlation is needed.

Radical prostatectomy: value of prostate MRI in surgical planning.

The introduction of serum prostate-specific antigen to the prostate cancer screening algorithm has led to an increase in prostate cancer diagnosis as well as a migration toward lower-stage cancer at the time of diagnosis. This stage migration has coincided with changes in treatment options; these include active surveillance, new therapies, and advances in surgical techniques. Use of robot-assisted radical prostatectomy (RARP) as a surgical technique has seen a significant increase over the past several years: the number of patients undergoing RARP has risen from 1% to 40% of all prostatectomies from 2001-2006 to as many as 80% in 2010. The robotic interface provides a 3D magnified view of the surgical field, intuitive instrument manipulation, motion scaling, tremor filtration, and excellent dexterity and range of motion. However, in some cases, the lack of tactile (haptic) feedback may limit the surgeon's decision making ability in assessing malignant involvement of the neurovascular bundles. Pre-operative planning relies on nomograms based on limited clinical and prostate biopsy information. The surgical decision to spare or resect the neurovascular bundles is based on clinical information which is not spatially or anatomically based. Advances in magnetic resonance imaging (MRI) may provide spatially localized information to fill this void and aid surgical planning, particularly for robotic surgeons. In this review, we discuss the potential role of pre-operative MRI in surgical planning for radical prostatectomy.

Prospective study comparing two techniques of renal clamping in laparoscopic partial nephrectomy: impact on perioperative parameters.

PURPOSE: To compare en bloc and artery-only clamping techniques on renal function and perioperative outcomes after laparoscopic partial nephrectomy (LPN). PATIENTS AND METHODS: From March 2003 to December 2008, 205 patients underwent LPN by one surgeon in a single institution. The first 103 LPNs were achieved with artery-only clamping (AO), and the last 102 LPNs were realized under control of the renal hilum (artery and vein [AV] clamping). Renal function was evaluated by creatinine changes, estimation of the glomerular filtration rate (eGFR), and assessment of split renal function using renal mercaptoacetyl triglycine-Lasix scintigraphy. Sixty-two of 205 patients had renal scintigraphy before and after surgery. RESULTS: There was no significant difference between the two groups regarding demographic data and renal mass characteristics. Warm ischemia time (WIT) was higher in the AO group: 30.4 ± 8.2 vs 23.3 minutes ± 10.0 (P<0.0001). The eGFR change was significantly lower in the AV group during the postoperative period: 10.2 mL/min vs 13.7 mL/min (P=0.0472). Operative blood loss, operative time, and complication rate were not statistically different between groups. Average loss of differential function of the operated kidney was 13.6 ± 9.2% for the AO group and 14.3 ± 12.3% for the AV group (P=0.8016). On multivariate analysis, clamping technique was not a predictive factor of renal function reduction. CONCLUSION: AV and AO techniques are associated with similar renal function outcomes in patients who were undergoing LPN. In our series, the AV technique was associated with a lower WIT, an important predictor of decrease in renal function.

The chromophobe tumor grading system is the preferred grading scheme for chromophobe renal cell carcinoma.

PURPOSE: The prognostic usefulness of the Fuhrman nuclear grading system has been questioned for chromophobe renal cell carcinoma due to its frequent nuclear and nucleolar pleomorphism. Chromophobe tumor grade, a novel 3-tier tumor grading system based on geographic nuclear crowding and anaplasia, was recently reported to be superior to the Fuhrman system. We compared the 2 scoring systems in a large sporadic chromophobe renal cell carcinoma cohort to determine which grading scheme provides the most predictive assessment of clinical risk. MATERIALS AND METHODS: We identified a total of 84 cases of sporadic chromophobe renal cell carcinoma in 82 patients from a total of 2,634 cases (3.2%) spanning 1989 to 2010. A subset of 11 tumors had secondary areas of sarcomatoid transformation. All cases were reviewed for Fuhrman nuclear grade and chromophobe tumor grade according to published parameters by an expert genitourinary pathologist blinded to clinicopathological information. RESULTS: The distribution of Fuhrman nuclear grades 1 to 4 was 0%, 52.4%, 32.9% and 14.7% of cases, and the distribution of chromophobe tumor grades 1 to 3 was 48.8%, 36.5% and 14.7%, respectively. Metastasis developed in 20 patients (24.4%). Survival analysis revealed statistically significant differences in recurrence-free survival when adjusted for chromophobe tumor grade and Fuhrman nuclear grade. Chromophobe tumor grade showed a slightly higher AUC for recurrence-free survival and overall survival than the Fuhrman nuclear grading system. Neither chromophobe tumor grade nor Fuhrman nuclear grade was retained as an independent predictor of outcome in multivariate modeling when patients with sarcomatoid lesions were excluded. CONCLUSIONS: Chromophobe tumor grade effectively stratifies patients with chromophobe renal cell carcinoma across all grading levels. Since it does not rely on nuclear features, it avoids the hazard of overestimating the malignant potential of chromophobe renal cell carcinoma. Overall chromophobe tumor grade has higher predictive accuracy than the Fuhrman nuclear grading system.

Urinary retention after orthotopic neobladder substitution in females.

PURPOSE: Urinary retention is a common complication after orthotopic neobladder urinary diversion. We reviewed a case series of women who underwent neobladder creation and discuss anatomical findings, and urinary retention etiology and prevention. MATERIALS AND METHODS: We retrospectively reviewed the records of all orthotopic neobladder urinary diversions in female patients performed at our institution from 1999 through 2010. We abstracted baseline clinical and demographic characteristics, operative information, and postoperative clinical, urodynamic, imaging and secondary procedure followup. We defined urinary retention as the need for intermittent catheterization. RESULTS: We identified 21 female patients who underwent neobladder diversion. Median age at cystectomy was 62 years (range 43 to 77). Median followup was 3 years (range 3 to 138 months). Of the patients 14 underwent ileocolic diversion, 6 underwent Studer ileal diversion and 1 underwent preservation of a right colon augmentation. All patients underwent prior or concurrent hysterectomy. In 2 patients with a history of genitourinary tuberculosis neobladder-vaginal fistulas developed postoperatively and they were excluded from analysis. Of the 19 female patients with a neobladder included in analysis 7 (36.8%) experienced urinary retention requiring clean intermittent catheterization. Associated abnormalities included neocystocele formation in 6 cases, anastomotic stricture in 1 and progressive neurological disease in 1. Upon straining the average neobladder descent was approximately 2 cm and the average change in the neocystourethral angle in patients with neocystoceles was 18 degrees. Of the patients 11 (57.9%) had a nonobstructive voiding pattern. CONCLUSIONS: Urinary retention in female patients with a neobladder can be functional, anatomical or multifactorial. In our series common anatomical findings associated with urinary retention were neocystocele formation and urethral kinking.

Basic research in kidney cancer.

CONTEXT: Advances in basic research will enhance prognosis, diagnosis, and treatment of renal cancer patients. OBJECTIVE: To discuss advances in our understanding of the molecular basis of renal cancer, targeted therapies, renal cancer and immunity, and genetic factors and renal cell carcinoma (RCC). EVIDENCE ACQUISITION: Data on recently published (2005-2011) basic science papers were reviewed. EVIDENCE SYNTHESIS: Advances in basic research have shown that renal cancers can be subdivided based on specific genetic profiles. Now that this molecular basis has been established, it is becoming clear that additional events play a major role in the development of renal cancer. For example, aberrant chromatin remodelling appears to be a main driving force behind tumour progression in clear cell RCC. A large number of potential biomarkers have emerged using various high-throughput platforms, but adequate biomarkers for RCC are still lacking. To bring the potential biomarkers and biomarker profiles to the clinical arena is a major challenge for the field. The introduction of tyrosine kinase inhibitors (TKIs) for therapy has shifted the interest away from immunologic approaches. Nevertheless, a wealth of evidence supports immunotherapy for RCC. Interestingly, studies are now appearing that suggest a combination of TKI and immunotherapy may be beneficial. Thus far, little attention has been paid to patient-specific differences. With high-throughput methods becoming cheaper and with the advances in sequencing possibilities, this situation is expected to change rapidly. CONCLUSIONS: Great strides have been made in the understanding of molecular mechanisms of RCC. This has led this field to the enviable position of having a range of molecularly targeted therapies. Large sequencing efforts are now revealing more and more genes responsible for tumour development and progression, offering new targets for therapy. It is foreseen that through integration of high-throughput platforms, personalised cancer treatment for RCC patients will become possible.

Basis for the use of localized hypothermia during radical pelvic surgery.

Controlled tissue cooling, or hypothermia, has been used therapeutically for decades to mitigate the negative effects of traumatic, ischemic, and surgical insults. When applied systemically, moderate hypothermia can attenuate or prevent the extent of neurologic sequelae. Localized hypothermia, on the other hand, has the capacity to reduce tissue edema, suppress inflammation, and minimize the severity of peripheral nerve injury. Therapeutic hypothermia has been used in critical care, neurosurgery, ophthalmology, otolaryngology, cardiothoracic surgery and most recently in urology. Nerve injury during radical pelvic surgery can result in urinary incontinence or retention, impotence and bowel dysfunction. Localized hypothermia during radical prostatectomy has demonstrated improved recovery of urinary continence and erectile function, and similar benefits might be observed in other types of radical pelvic surgery.

Multivariate analysis of the factors involved in loss of renal differential function after laparoscopic partial nephrectomy: a role for warm ischemia time.

BACKGROUND: Partial nephrectomy (PN) is now the gold standard for the surgical treatment of small renal masses. We evaluated the effect of WIT and other factors on RDF assessed by preoperative and postoperative renal scintigraphy. METHODS: Between 2003 and 2008, 182 consecutive laparoscopic PN (LPN) were performed in an academic centre. Among those, 56 had mercaptoacetyl triglycine (MAG3) lasix renal scintigraphy preoperatively and postoperatively. RESULTS: Medians for age, preoperative estimated glomerular filtration rate and computed tomography scan tumour size were 62 years, 82 mL/min/1.73m(2) and 26 mm, respectively. Median WIT and preoperative RDF were 30 minutes and 50%, respectively. Median loss of RDF after surgery was 14%. Linear regression curves showed that loss in RDF rate was 0.2% per minute when WIT was <30 minutes and 0.7% per minute when WIT was ≥30 minutes. In multivariate analysis, length of WIT and endophytic tumour location were associated with a statistically significant loss of RDF (p < 0.05), but only in the group who experienced >30 minutes of WIT. INTERPRETATION: Our results suggest that the factors associated with loss of RDF are not the same before and after 30 minutes of WIT and that the rate of loss in RDF increases after 30 minutes. Since, the effect of WIT is small up to 30 minutes, we believe that surgery should focus on limiting the resection of normal parenchyma and to ensure negative margins and hemostasis, rather than on premature unclamping.

Purification and direct transformation of epithelial progenitor cells from primary human prostate.

Epithelial cell transformation has been demonstrated in numerous animal models for the study of solid tumor biology. However, little evidence exists for human epithelial cell transformation without previous immortalization via genetic influences such as SV40 T-antigen, thus limiting our knowledge of the events that can transform naive human epithelium. Here we describe a system developed in our laboratory to directly transform freshly isolated primary human prostate epithelial cells without previous culture or immortalization. Prostate tissue is obtained from patients and benign tissue is separated from malignant tissue. Benign and malignant tissues are mechanically and enzymatically dissociated to single cells overnight, and immune cells and epithelial subsets are isolated on the basis of differential expression of surface antigens. Epithelial progenitor cells are transduced with lentiviruses expressing oncogenes and combined with inductive stroma for in vivo studies. At 8-16 weeks after transplantation into immune-deficient mice, the development of lesions, histologically classified as benign prostate, prostatic intraepithelial neoplasia and adenocarcinoma, can be evaluated.