The Influence of the Intraductal Carcinoma of the Prostate on the Short-Term Oncological Outcomes

Aim: The presence of intraductal carcinoma of the prostate (IDC-P) in radical prostatectomy (RP) specimens correlates with adverse prognostic factors such as worse biochemical recurrence-free survival, higher grade and stage disease. This study aimed to investigate the effect of IDC-P in radical prostatectomy specimens on short-term oncological outcomes. Materials and methods: Patients who underwent RP at our clinic for prostate cancer between May 2016 and November 2019 were included in the study. They were divided into two groups based on the presence of IDC-P in RP specimens. Their clinical, pathological, and oncologic data were evaluated retrospectively. Results: A total of 98 patients underwent RP with a mean age of 65.5 years (50-83) and a mean follow-up time of 31.2 months (6-52). Seventy and 28 patients were evaluated in the group without IDC-P and group with IDC-P, respectively. Surgical margin positivity (p=0.307) and lymph node metastasis (p=0.017) rates were higher in the group with IDC-P. Although there were no statistical differences between the groups, at follow-up biochemical recurrence rate (p=0.052) was higher, and mean time to biochemical recurrence rates were lower (p=0.057) in the group with IDC-P. The group with IDC-P was associated with a 3-fold increase in prostate cancer-specific mortality to the group without IDC-P (p=0.037). Conclusions: Patients with IDC-P at RP specimens have more advanced disease, shorter biochemical recurrence-free, and cancerspecific survival than those without IDC-P. Defining the presence of IDC-P in RP specimens is critical in choosing the appropriate treatment strategy and predicting the prognosis (AU)

Objetivo: La presencia de carcinoma intraductal dela próstata (IDC-P) en muestras de prostatectomía radical(RP) se correlaciona con factores de pronóstico adversotales como peor recurrencia bioquímica de supervivenciasin la enfermedad, así como mayor grado y estadío másavanzado de la enfermedad. El objetivo de este estudio erainvestigar el efecto de la IDC-P en muestras de prostatectomía radical en resultados oncológicos a corto plazo.Materiales y procedimientos: En este estudio hansido incluidos los pacientes que fueron sometidos a una RPdebido a cáncer de próstata en nuestra clínica entre mayodel 2016 y noviembre del 2019. Fueron divididos en dosgrupos según la presencia de IDC-P en sus muestras RP.Sus datos clínicos, patológicos y oncológicos fueron evaluados retrospectivamente.Resultados: Un total de 98 pacientes fueron sometidos a una RP con una edad media de 65,5 años (50-83) ycon un periodo de seguimiento medio de 31,2 meses (6-52). Se evaluaron 70 y 28 pacientes en el grupo sin IDCP y en el grupo con IDC-P, respectivamente. Dentro delgrupo con IDC-P, las tasas de positividad de margen quirúrgico (p=0,307) y metástasis en nodos linfáticos (p=0,017)son más elevadas. A pesar de no haber diferencias estadísticas entre ambos grupos, la tasa de recurrencia químicadurante el seguimiento (p=0,052) es más elevada y la tasadel tiempo medio hasta la recurrencia química (p=0,057)es menor en el grupo con IDC-P. El grupo con IDC-P hasido asociado a un aumento de la moralidad específica delcáncer de próstata 3 veces superior al del grupo sin IDC-P(p=0,037).Conclusiones: Los pacientes con IDC-P en las muestras RP se encuentran en en estadío de la enfermedad másavanzada, así como una recurrencia bioquímica sin la enfermedad y una supervivencia específica más cortas que aquellos sin IDC-P. La determinación de la presencia de IDC-Pen muestras RP es crítica a la hora de elegir una estrategiade tratamiento adecuada y la predicción del pronóstico (AU)

The effect of surgical margin on cancer-specific survival in patients treated with nephron-sparing surgery.

BACKGROUND: Nephron-sparing surgery (NSS) is currently the recommended treatment modality for selected renal tumors. The prognostic significance of positive surgical margin (PSM) and surgical margin width (SMW) after NSS is controversial. AIM: To evaluate the effect of PSM and SMW on cancer-specific survival (CSS) in patients who underwent NSS. MATERIALS AND METHODS: The pathological samples of 142 patients who underwent NSS were reviewed. Patients were divided into two groups with PSM and negative surgical margin (NSM), and after that those with PSM were divided into two groups according to SMW as those with 0.1-2 mm and those >2 mm. CSS was calculated using Kaplan-Meier method. Cox regression analysis was used to adjust the clinicopathologic variables. A P value < 0.05 was considered statistically significant. RESULTS: Local recurrence rate and distant metastasis rate were higher in patients with PSMs than those with NSMs (P = 0.018 and P = 0.039, respectively). However, there was no significant difference between the two groups in terms of CSS. In the group with SMW 0.1-2 mm, the tumor diameter was longer (P = 0.018), enucleation number was higher (P = 0.026), and local recurrence was higher (P = 0.034) than the group with SMW > 2 mm. There was no significant difference between the two groups in terms of CSS. CONCLUSION: In patients who underwent NSS, PSMs and SMWs have a negative effect on local recurrence but have no significant effect on CSS.

Prediction of aggressiveness of gastrointestinal stromal tumours based on immunostaining with bcl-2, Ki-67 and p53.

OBJECTIVE: While the use of fine needle aspiration (FNA) in the diagnosis of gastrointestinal stromal tumours (GISTs) is well-established, it can be difficult to predict the prognosis of GIST based on morphology alone. The objective of the current study was to determine if expression of bcl-2, Ki-67 and p53 correlated with the outcome of GISTs based on cytological material. METHODS: Cell-blocks from 14 GISTs diagnosed by FNA were retrieved. Immunostaining was performed with antibodies against bcl-2, Ki-67 and p53. All cytological diagnoses were confirmed by positive immunostaining with c-kit and/or subsequent histological evaluation. Positivity for bcl-2, Ki-67 and p53 was defined as the presence of > or =10% cytoplasmic staining, > or =5% nuclear staining and > or =5% nuclear staining respectively. RESULTS: The 14 patients consisted of seven males and seven females with a mean age of 58 years. The average follow-up interval was 46 months. Six had a benign course and eight developed recurrences/metastases. Thirteen (93%) cases showed positive staining for bcl-2. Positive Ki-67 and p53 staining was noted in one (7%) and seven (50%) cases respectively. The difference in staining for p53 between aggressive and non-aggressive GISTs was statistically significant. No statistically significant difference was noted for bcl-2 staining or Ki-67 labelling index between the two groups. CONCLUSIONS: According to our observations, p53 immunostaining may be useful in predicting the outcome of GIST diagnosed by FNA; Ki-67 and bcl-2 are not useful as prognostic markers for GIST in FNA specimens.

Obstacles to the early detection of endocervical adenocarcinoma.

We observed that the ratio of in situ to invasive carcinomas of the cervix is significantly greater for squamous than for glandular lesions. We wondered whether Pap smears were less effective for the identification of in situ glandular lesions. The purpose of this study was to determine if the location, extent of disease, and growth patterns of endocervical adenocarcinomas influence the ability to detect malignant cells by Pap smears. Medical records, doctor's office records, and all pathology materials (reports and slides) including Pap smears, biopsies, LEEP/cone biopsies, and hysterectomy specimens from 53 consecutive patients diagnosed with endocervical adenocarcinomas were examined at New York University Medical Center (a total of 654 pathology slides and 51 Pap smears were reviewed). Findings were correlated for each patient using gross descriptions and histopathology and stratified by location/extent of disease and growth pattern (exophytic or endophytic or both). Ten patients had in situ disease, seven (70%) of which involved the transformation zone (TZ); all seven of these were identified by Pap smears. In contrast, of the other three cases that did not involve the TZ but were confined to the endocervix, only one was identified by Pap smear. Forty-three patients had invasive disease. Twenty involved the TZ, and 23 involved the endocervix but spared the TZ. Of the 20 tumors involving the TZ, 11 (55%) were identified by Pap smears, whereas of the 23 sparing the TZ, 11 (47.8%) were diagnosed by Pap smear. Among the 23 patients with invasive disease that spared the TZ, 6 (26%) had a documented history of negative Pap smears at New York University within 3 years of diagnosis. Conversely only 1 of the 20 patients with TZ involvement had a history of negative Pap smears, and 3 patients in this group denied having had Pap smears for several years. Including all 53 patients, a significantly higher proportion were not detectable by Pap smear if the TZ was spared (54% versus 25%, p = 0.036). Of the 23 invasive cancers that spared the TZ, 6 (14%) had verified negative Pap smears. These lesions did not shed malignant cells onto Pap smears. Noteworthy was the finding that two of these six lesions extended from the endocervix upward, through the stroma, and into the endomyometrium of the lower uterine segment. Four extended downward into the exocervix through the stroma, sparing the surface mucosa; one reached the upper vagina. All six displayed an endophytic growth pattern.

Extrapulmonary tuberculosis as a mimicker of neoplasia.

Despite the efforts for control and eradication of tuberculosis, new cases of the disease are diagnosed daily. The diagnosis of tuberculosis is easily made when the classical features of pulmonary necrotizing granulomatous inflammation are seen. However, extrapulmonary lesions may clinically and radiographically mimic a neoplastic process, and this may lead to misdiagnosis and delay in treatment. We studied 6 patients by aspiration biopsy, all recent immigrants and immunocompetent, who presented with weight loss and fatigue. Of these, 5 patients had a mass. One patient presented with a lytic lesion of bone. In all cases the clinical diagnosis was neoplasia. In all aspirates, the smears showed necrotic debris with neutrophils. No neoplastic cells or granulomas were seen. All cases were signed out descriptively with no specific diagnosis. A search for acid-fast organisms leading to the correct diagnosis of tuberculosis was prompted by clinical investigations that revealed pulmonary lesions, or by repeat aspiration biopsy, which showed granulomatous inflammation. Tuberculosis when present in atypical forms is still a challenging diagnosis. The finding of necrotic debris in a needle biopsy without the clinical signs of an abscess should prompt a search for acid-fast bacilli, since the correct diagnosis will eliminate a needless surgical procedure and will lead to timely and appropriate therapy.

Fibroadenomas with atypia: causes of under- and overdiagnosis by aspiration biopsy.

Fibroadenoma (FA) is a common benign breast lesion frequently sampled by fine-needle aspiration biopsy (FNAB). Although the cytologic diagnosis is straightforward in most cases, cellular discohesion and atypia in FAs may lead to falsely atypical or positive FNAB diagnoses. Conversely, some adenocarcinomas mimic a fibroadenomatous pattern on FNAB, resulting in a false-negative diagnosis. We reviewed the cytologic and histologic findings in 25 cases with a preoperative FNAB diagnosis of FA, wherein excision was recommended based on atypia. Our aim was to analyze the spectrum of changes causing under- or overdiagnosis in such cases. The smears were assessed for cellularity, cellular discohesion, presence of dissociated intact cells and nucleoli, nuclear pleomorphism, oval bare nuclei, and stromal fragments. The histologic findings were correlated with FNAB features. At excision, 88% of FAs classified as atypical on FNAB were benign (FA with ductal hyperplasia and lactational change, myxoid FA, and other fibroepithelial lesions). Differentiating myxoid FA from colloid carcinoma was difficult due to the abundance of extracellular mucin in which the dissociated epithelial cells were floating. Two (8%) cases were carcinomas on excision; the reasons for underdiagnosis in one case reflected sampling, and in the other, interpretative error. There was one (4%) benign phyllodes tumor which lacked stromal fragments and single stromal cells on FNAB smears. The lesion was called atypical, based on the epithelial discohesion on the smears. We conclude that the majority of FAs with atypia on FNAB are benign lesions. Considering the grave consequences of a false-positive cytologic diagnosis, we recommend a conservative approach in interpreting FNAB smears which overall display a fibroadenomatous pattern.

Cytologic features of tubular adenocarcinoma of the breast by aspiration biopsy.

Tubular adenocarcinoma is an invasive mammary adenocarcinoma associated with an excellent prognosis and a low incidence of axillary metastases. However, identification of tubular adenocarcinoma by fine-needle aspiration (FNA) biopsy has proven difficult. One hundred five patients with documented "pure" tubular adenocarcinoma were diagnosed at Tisch Hospital from August of 1992 to December of 1998. Twenty-one of these patients had an FNA before excision. We reviewed the smears of these cases and compared them with cases of fibroadenoma and fibrocystic change to identify criteria for diagnosis. Moderately to highly cellular smears with angular cellular clusters with sharp borders and oval cells outlining these clusters, dispersed single cells with minimal atypia, and the absence or paucity of dispersed bare oval nuclei in the background were features that suggest a diagnosis of tubular adenocarcinoma in our study. Attention to these features in combination with appropriate mammographic findings should preclude a false-negative diagnosis in the majority of cases of tubular adenocarcinoma diagnosed by aspiration biopsy. We point to the presence of the peripheral perpendicular cells in the characteristic tubular arrays as an important clue to the diagnosis of tubular adenocarcinoma.

Absence of SV-40 large T antigen (Tag) in malignant mesothelioma effusions: an immunocytochemical study.

Simian Virus 40 (SV 40) was recently implicated in the pathogenesis of malignant mesothelioma. The oncogenic capacity of SV-40 is a function of a nuclear protein, the large T antigen (Tag). SV-40 Tag DNA sequences are detected by the polymerase chain reaction in 40-80% of malignant mesothelial proliferations. However, the role of immunohistochemistry (IHC) in demonstrating the nuclear localization of Tag is controversial. We sought to determine the clinical utility of SV-40 Tag IHC in pleural effusion cytology as an ancillary tool in the cytologic diagnosis of malignant mesothelioma (MM). Formalin-fixed, paraffin-embedded cell block sections from 100 pleural effusions (32 MMs, 25 benign reactive, 43 metastatic adenocarcinomas) were immunostained for the SV-40 anti-Tag, using two primary monoclonal SV-40 Tag antibodies: clone Pab 416 and clone Pab 101. Despite strong and consistent immunoreactivity in positive controls, no nuclear immunostaining was observed in any case. We believe the small sample size in cytology cell block sections, the low viral copy number in infected cells, and the effect of formalin fixation may have resulted in absence of immunoreactivity. The role of SV-40 Tag IHC in diagnostic cytopathology remains unclear unless further studies reliably show its detection.

Endometriosis in abdominal scars: a report of three cases diagnosed by fine-needle aspiration biopsy.

Endometrioma in an operative scar is rare. The majority of patients have no prior history of endometriosis, and symptoms may mimic postoperative hernias. Fine-needle aspiration biopsy (FNAB) can be a valuable diagnostic aid in the evaluation of these subcutaneous abdominal masses. We present the cytologic findings in three cases of abdominal wall endometriomas diagnosed by FNAB. The patients ranged from 31 to 51 years of age. None had a history of endometriosis, but all had prior abdominal operations (two abdominal hysterectomies for fibroids and one cesarean section). They presented 6 months to 7 years later with painful subcutaneous abdominal nodules in their scars ranging from 2 to 6 cm. FNAB was performed by a cytopathologist. The smears were cellular and comprised two distinct cell populations. An epithelial component consisted of flat sheets of polygonal cells with round to oval nuclei and scant cytoplasm. The second component consisted of clusters of fusiform stromal cells. Numerous hemosiderin-laden macrophages were noted in the background. Cytokeratin highlighted the epithelial clusters, and vimentin stained the stromal cells. Electron microscopy showed two epithelial cell types: one with cilia and abundant rough endoplasmic reticulum and the other with numerous microvilli and scattered mitochondria indicative of endometrial differentiation. FNAB provided a rapid and accurate preoperative diagnosis in each case.

Comparison of antibodies to HBME-1 and calretinin for the detection of mesothelial cells in effusion cytology.

The distinction of mesothelial cells in cytologic samples is often a diagnostic challenge. This is particularly true in potentially malignant effusions in which reactive mesothelial cells may simulate adenocarcinoma (ACA) cells, and in the differentiation of ACA vs. mesothelioma. We sought to determine the superior antibody for the positive identification of mesothelial cells in these circumstances. Cell block sections of 25 reactive and 8 malignant mesothelioma effusions were immunostained with an avidin-biotin procedure, using antibodies to HBME-1 and calretinin. No pretreatment of samples was necessary for the HBME-1-stained slides; microwave antigen retrieval was performed on all slides stained for calretinin. A negative control was performed on each sample. The staining intensity of tumor cells was scored on a scale of 0-3+, with the proportion of immunoreactive cells categorized as <25%, 25-50%, 50-75%, and >75%. The predominant staining pattern for HBME-1 was surface, with rare samples also exhibiting cytoplasmic staining as well. The calretinin-staining pattern was cytoplasmic, with peripheral condensation/prominence and accompanying nuclear staining. All samples were immunoreactive with both antibodies. Fifty-five percent (18/33) of samples showed significantly stronger immunoreactivity with calretinin than with HBME-1; 45% (15/33) of samples showed equivalent staining with the two markers. None of the samples in this study showed stronger immunoreactivity with HBME-1 than with calretinin. Sixty-one percent (20/33) of samples stained with HBME-1 at a moderate (2+) intensity. Fifty-five percent (18/33) of samples stained with calretinin at a strong (3+) intensity. While only 12% of samples showed >75% immunoreactivity for HBME-1, 58% of samples showed >75% of cells immunoreactive for calretinin. Calretinin is the preferred marker in identifying mesothelial cells in cytologic samples, showing the highest sensitivity for mesothelial cells, as evidenced by a more intense staining reaction in a higher percentage of cells than with HBME-1. Published 2001 Wiley-Liss, Inc.

Aspiration cytology of the collagenized variant of mammary myofibroblastoma: a case report with review of the literature.

Myofibroblastoma of the breast is a rare benign stromal neoplasm, which occurs primarily in men. Classical myofibroblastoma is a circumscribed, nonencapsulated tumor comprised of bipolar fusiform cells arranged randomly, or in fascicles alternating with broad collagenous bands. Additional histologic variants (the cellular, collagenized, infiltrative, and epitheloid types) have been described. Several case reports describe the cytopathologic features of the classical and cellular variants. We report on a 70-yr-old woman, who presented with a circumscribed mass in her left breast. Aspiration biopsy showed paucicellular smears with singly distributed atypical spindle-shaped cells and rare fragments of collagenized stroma, raising suspicion of a phyllodes tumor. Histologic examination revealed spindle-shaped cells distributed in a diffusely collagenized stroma. Some nuclear atypia was present. To the best of our knowledge, this is the first case reporting the cytologic features of the collagenized variant of myofibroblastoma. Although we believe a specific diagnosis of myofibroblastoma can be rendered in a male based on the typical cytologic and clinical findings in the classical type, the variant forms are difficult to classify accurately and require excision for a definitive diagnosis.

Detection of loss of heterozygosity at chromosome 3p25-26 in primary and metastatic ovarian clear-cell carcinoma: utilization of microdissection and polymerase chain reaction in archival tissues.

Loss of heterozygosity (LOH) at the 3p region is found in up to 50% of epithelial ovarian neoplasms. The von Hippel-Lindau (VHL) gene at the 3p25 locus is one of the tumor-suppressor genes located at 3p. The role, if any, of the VHL gene locus is not clear in ovarian carcinogenesis. We analyzed primary and metastatic ovarian clear-cell carcinomas (OCCC) for LOH at 3p25 to determine its frequency and its diagnostic utility as an adjunctive tool in the differential diagnosis of metastatic clear-cell carcinomas. Microdissection followed by single-step DNA extraction and polymerase chain reaction (PCR) amplification, using two polymorphic markers flanking the VHL gene locus, was done on archival histology and cytology samples from 9 patients with metastatic OCCC. Of the informative cases, 43% of the metastatic and 50% of the primary OCCC showed LOH. LOH at the VHL gene locus is not uncommon in clear-cell ovarian carcinoma. LOH at 3p25 in cytologic specimens may be a valuable adjunct in the diagnosis of OCCC metastasis in cytologically equivocal cases. OCCC should enter the differential in clear-cell carcinomas of unknown primary that show LOH at 3p25. Published 2001 Wiley-Liss, Inc.

Repeat cervical cytology at the time of colposcopy. Is there an added benefit?

OBJECTIVE: To determine if repeating the Pap smear (PS) at colposcopy offers added benefit in the detection of cervical squamous intraepithelial lesions (SILs). STUDY DESIGN: Eight hundred fifty-two women were subjects of this study. Patients with cervical SIL were defined as women with SIL on the repeat PS, or SIL on the colposcopic cervical biopsy (bx) or a negative repeat PS and bx but confirmed SIL on both the previous and follow-up PS or bx. The sensitivities of repeat PS and bx in detecting SIL were calculated. The chi 2 test was used to assess statistical significance. The total cost of repeating the PS was calculated by multiplying the total number of patients (852) by the estimated cost of a single PS ($25). RESULTS: The sensitivities of repeat PS, bx and PS/bx combined were .89, .69 and .92 for low grade SIL (LSIL) and .74, .77 and .98 for high grade SIL (HSIL), respectively (P < .0001). Sixteen percent of the HSIL and 28% of the LSIL cases were diagnosed on repeat PS only (negative bx). If repeat PS was omitted, $21,300 would have been saved.

Rhodococcus equi and cytomegalovirus pneumonia in a renal transplant patient: diagnosis by fine-needle aspiration biopsy.

Rhodococcus equi is a common cause of pneumonia in animals. Human infection is rare. Increasing number of cases are being reported in immunosuppressed individuals mostly associated with HIV infection, but also in solid organ transplant recipients and leukemia/lymphoma patients. We report on an adult male who developed pneumonia and gastroenteritis 4 mo after receiving a renal transplant. CT scan of the lungs showed a dominant 2.5-cm upper lobe lung mass and smaller bilateral nodules. He underwent a diagnostic bronchoscopy with fine-needle aspiration biopsy of the largest lung nodule. Smears showed histiocytic granulomatous inflammation, foamy macrophages, and acute inflammatory exudate. Scattered foamy macrophages displayed intracellular coccobacilli identifiable on Diff-Quik stain. A few cells with changes suggestive of viral inclusions were identified. Cytomegalovirus (CMV) immunostain was positive in the cell block sections. Lung cultures grew R. equi. To the best of our knowledge, this is the first report of coinfection with R. equi and CMV.

Human papillomavirus absence predicts normal cervical histopathologic findings with abnormal papanicolaou smears: a study of a university-based inner city population.

INTRODUCTION: We studied the role of human papillomavirus (HPV) typing in predicting cervical dysplasia in women with abnormal Papanicolaou (Pap) test results. STUDY DESIGN/METHODS: A university colposcopy clinic-based consecutive sample of 179 women completed a questionnaire and underwent colposcopy, HPV typing (Hybrid Capture System HPV DNA Assay II; Digene Diagnostics, Gaithersburg, MD, USA), and biopsy (if indicated). RESULTS: No severe dysplasia was observed in women with low-risk HPV or in women with negative HPV test results who had a low-grade abnormality on the Pap test. High-risk (HR) HPV was present in every case of severe dysplasia on biopsy. The cumulative odds risk for cervical dysplasia was 1.11 in HIV(+) women with low-grade squamous intraepithelial lesion on the Pap test who were older than 21 years of age and HPV-HR(+). CONCLUSIONS: In the population studied, HPV typing is a valuable adjunct to a low-grade abnormality on the Pap test in predicting the absence of cervical dysplasia on biopsy. Larger prospective population-based studies are needed to study the role of HPV as a negative predictor of disease in cervical dysplasia.

Diffuse alveolar damage. Morphologic features in bronchoalveolar lavage fluid.

OBJECTIVE: To evaluate the overall cytologic characteristics of diffuse alveolar damage (DAD) in bronchoalveolar lavage (BAL) specimens in search of features that could be useful in cytologic diagnosis. STUDY DESIGN: We evaluated BAL samples from patients with DAD obtained simultaneously with transbronchial biopsies (n = 8) or open lung biopsies (n = 2) or within 24 hours of autopsy (n = 2). The material was processed routinely for cytologic and histologic evaluation. RESULTS: The smears were moderately to highly cellular. All cases had large numbers of alveolar macrophages and/or desquamated alveolar cells. The epithelial component displayed various degrees of nuclear atypia. Some epithelial clusters were three-dimensional, with peripheral cells showing clear cytoplasm, protruding outwards and resembling hobnails. Other aggregates appeared two-dimensional, as sheets of cells with flattened and dense cytoplasm (squamotized). Both types of cell clusters were often associated with dense, basophilic or amphophilic, amorphous extracellular material. Counterparts of all the cytologic features were observed in the histologic material, including atypia of the alveolar lining with hobnailing, squamotization, amorphous extracellular material and hyaline membranes. CONCLUSION: The cytologic features of BAL represent a constellation of alveolar cell injury. Based on these features, DAD can be correctly diagnosed or suggested in BAL samples in the appropriate clinical setting.

Human polyoma virus in renal allograft biopsies: morphological findings and correlation with urine cytology.

Human polyoma virus (PV) interstitial nephritis occurs in immunosuppressed patients after reactivation of latent virus in renal epithelium. Currently, there is neither general consensus about the incidence of clinically significant PV infection in renal transplants nor conclusive evidence determining its significance in the long-term graft outcome. We evaluated 601 renal transplant biopsy specimens (from 365 patients) by routine light microscopy and immunoperoxidase stains with antibody against SV40 (which cross reacts with PV). We also examined urine samples from 200 patients (100 obtained concurrently with a renal biopsy in patients presenting with acute graft dysfunction and 100 from patients with stable graft function). Electron microscopic evaluation was performed in 50 renal biopsy specimens and in 23% of all urine samples. PV was identified in 1.8% biopsy specimens (1.9% of patients). PV interstitial nephritis showed the typical viral cytopathic changes in tubular epithelial cells associated with marked tubular damage and a disproportionately mild degree of tubulitis. There was no difference in the incidence of PV in the urine of patients with acutely deteriorating versus stable renal function (18% and 19%, respectively); however, urines with large numbers of infected cells (> 10/cytospin) and inflammatory changes in the sediments corresponded invariably to patients with acute allograft dysfunction (8 of 8), and in most cases to biopsy specimens showing PV interstitial nephritis (7 of 8). Based on these findings, urine samples seem to be the most sensitive and cost-effective screening method for PV infection; only urine samples with inflamed sediments and abundant infected cells correlate with clinically significant disease. In these cases, examination of a renal biopsy is indicated. Immunohistochemical stains are useful to confirm the presence of PV but do not increase the sensitivity of diagnosis of PV if this is not already suspected on routine light microscopy. In our material, immunostains were helpful ruling out the presence of PV in a small number of biopsy specimens (2%) that showed markedly reactive tubular cells resembling PV infection. Most patients with PV interstitial nephritis responded to decreased immunosuppression; however, the decay in graft function (based on creatinine slopes) was significantly more rapid in these patients than in matched controls. Evidence of PV infection should be systematically sought in renal biopsy specimens and urine samples from renal allograft recipients.