Is prostatic intraepithelial neoplasia in the transition/central zone a true precursor of cancer? A long-term retrospective study in Norway

Preneoplasia in the prostate gland with emphasis on high grade prostatic intraepithelial neoplasia

There are a variety of morphological patterns and processes that have been implicated in the pathogenesis of prostate cancer. Prostatic intraepithelial neoplasia (PIN), inflammation with or without atrophy, and adenosis (atypical adenomatous hyperplasia) have all been given candidate status as precursor lesions of prostatic adenocarcinoma. Based on decades of research, high grade prostatic intraepithelial neoplasia (HPIN), a proliferative lesion of prostatic secretory cells, has emerged as the most likely morphological pre-invasive lesion involved in the evolution of many but not all prostatic adenocarcinomas. In this manuscript, we briefly discuss other proposed precursors of prostatic adenocarcinoma and then focus on the history, diagnostic criteria and morphology of HPIN. The incidence of HPIN and its relationship to prostate cancer is reviewed. The differential diagnosis of large glandular patterns in the prostate is discussed in depth. Finally, we summarise the recent clinicopathological studies evaluating the clinical significance of HPIN and discuss follow-up strategies in men diagnosed with HPIN.

Tumor-infiltrating immune cells promoting tumor invasion and metastasis: existing theories

It is a commonly held belief that infiltration of immune cells into tumor tissues and direct physical contact between tumor cells and infiltrated immune cells is associated with physical destructions of the tumor cells, reduction of the tumor burden, and improved clinical prognosis. An increasing number of studies, however, have suggested that aberrant infiltration of immune cells into tumor or normal tissues may promote tumor progression, invasion, and metastasis. Neither the primary reason for these contradictory observations, nor the mechanism for the reported diverse impact of tumor-infiltrating immune cells has been elucidated, making it difficult to judge the clinical implications of infiltration of immune cells within tumor tissues. This mini-review presents several existing hypotheses and models that favor the promoting impact of tumor-infiltrating immune cells on tumor invasion and metastasis, and also analyzes their strength and weakness.

A seemingly most effective target for early detection and intervention of prostate tumor invasion

This commentary proposes that budding tumor cell projections from focally disrupted tumor capsules represent a most effective target for early detection and intervention of prostate tumor invasion. The rationale, supporting data, and clinical applications of the hypothesis are discussed.

Correlated alterations in prostate basal cell layer and basement membrane

Our recent studies revealed that focal basal cell layer disruption (FBCLD) induced auto-immunoreactions represented a contributing factor for human prostate tumor progression and invasion. As the basement membrane surrounds and attaches to the basal cell layer, our current study assessed whether FBCLD would impact the physical integrity of the associated basement membrane. Paraffin sections from 25-human prostate tumors were subjected to double immunohistochemistry to simultaneously elucidate the basal cell layer and the basement membrane with corresponding biomarkers. The physical integrity of the basement membrane overlying FBCLD was examined to determine the extent of correlated alterations. Of a total of 89 FBCLD encountered, 76 (85 %) showed correlated alterations in the overlying basement membrane, which included distinct focal disruptions or fragmentations. In the remaining 13 (15%) FBCLD, the overlying basement membrane showed significant attenuation or reduction of the immunostaining intensity. The basement membrane in all or nearly all ducts or acini with p63 positive basal cells was substantially thicker and more uniform than that in ducts or acini without p63 positive basal cells, and also, a vast majority of the focal disruptions occurred near basal cells that lack p63 expression. These findings suggest that focal disruptions in the basal cell layer and alterations in the basement membrane are correlated events and that the physical and functional status of the basal cells could significantly impact the physical integrity of the overlying basement membrane. As the degradation of both the basal cell layer and the basement membrane is a pre-requisite for prostate tumor invasion or progression, ducts or acini with focally disrupted basal cell layer and basement membrane are likely at greater risk to develop invasive lesions. Thus, further elucidation of the specific molecules and mechanism associated with these events may lead to the development of a more effective alternative for repeat biopsy to monitor tumor progression and invasion.

Bad seeds produce bad crops: a single stage-process of prostate tumor invasion

It is a commonly held belief that prostate carcinogenesis is a multi-stage process and that tumor invasion is triggered by the overproduction of proteolytic enzymes. This belief is consistent with data from cell cultures and animal models, whereas is hard to interpret several critical facts, including the presence of cancer in "healthy" young men and cancer DNA phenotype in morphologically normal prostate tissues. These facts argue that alternative pathways may exist for prostate tumor invasion in some cases. Since degradation of the basal cell layer is the most distinct sign of invasion, our recent studies have attempted to identify pre-invasive lesions with focal basal cell layer alterations. Our studies revealed that about 30% of prostate cancer patients harbored normal appearing duct or acinar clusters with a high frequency of focal basal cell layer disruptions. These focally disrupted basal cell layers had significantly reduced cell proliferation and tumor suppressor expression, whereas significantly elevated degeneration, apoptosis, and infiltration of immunoreactive cells. In sharp contrast, associated epithelial cell had significantly elevated proliferation, expression of malignancy-signature markers, and physical continuity with invasive lesions. Based on these and other findings, we have proposed that these normal appearing duct or acinar clusters are derived from monoclonal proliferation of genetically damaged stem cells and could progress directly to invasion through two pathways: 1) clonal in situ transformation (CIST) and 2) multi-potential progenitor mediated "budding" (MPMB). These pathways may contribute to early onset of prostate cancer at young ages, and to clinically more aggressive prostate tumors.

Prostatic intraepithelial neoplasia: recent advances

CONTEXT

There have been 2 putative prostatic cancer precursors, prostatic intraepithelial neoplasia (PIN) and atypical adenomatous hyperplasia (adenosis), but PIN remains as a well-known precancerous condition.

OBJECTIVE

To describe recent advances in knowledge of PIN and to better define the diagnostic criteria and differential diagnosis of PIN.

DATA SOURCES

Review of the pertinent literature and our experience.

CONCLUSIONS

The presence of ductal/acinar epithelial changes including nuclear enlargement, prominent nucleoli, chromatin alterations, and luminal complexity is an easy way to identify the disorder. Four main patterns of high-grade PIN (HGPIN) have been described: tufting, micropapillary, cribriform, and flat. In addition, variants of HGPIN have also been described. Both HGPIN and prostatic carcinoma share an increased incidence and severity with advancing age and with high rates of occurrence in the peripheral zone of the prostate. Furthermore, HGPIN and prostate cancer share genetic and molecular markers as well, with PIN representing an intermediate stage between benign epithelium and invasive carcinoma. The clinical significance of HGPIN is that it identifies patients at risk for prostatic carcinoma. With the increased use of extended biopsy protocols, clinicians are more likely to identify HGPIN and less likely to miss concurrent carcinoma.

Focal degeneration of basal cells and the resultant auto-immunoreactions: a novel mechanism for prostate tumor progression and invasion

The development of human prostate cancer is believed to be a multistep process, progressing sequentially from normal, to hyperplasia, to prostatic intraepithelial neoplasia (PIN), and to invasive and metastatic lesions. High grade PIN has been generally considered as the direct precursor of invasive lesions, and the progression of PIN is believed to be triggered primarily, if not solely, by the overproduction of proteolytic enzymes predominately by cancer cells, which result in the degradation of the basement membrane. These theories, however, are hard to reconcile with two main facts: (1) only about 30% untreated PIN progress to invasive stage, while none of the current approaches could accurately identify the specific PIN or individuals at greater risk for progression, and (2) results from recent world-wide clinical trials with a wide variety of proteolytic enzyme inhibitors have been very disappointing, casting doubt on the validity of the proteolytic enzyme theory. Since over 90% of prostate cancer-related deaths result from invasion-related illness and the incidence of PIN could be up to 16.5-25% in routine or ultrasound guided prostate biopsy, there is an urgent need to uncover the intrinsic mechanism of prostate tumor invasion. Promoted by the facts that the basal cell population is the source of several tumor suppressors and the absence of the basal cell layer is the most distinct feature of invasive lesions, our recent studies have intended to identify the early alterations of basal cell layers and their impact on tumor invasion using multidisciplinary approaches. Our studies revealed that a subset of pre-invasive tumors contained focal disruptions (the absence of basal cells resulting in a gap greater than the combined size of at least three epithelial cells) in surrounding basal cell layers. Compared to their non-disrupted counterparts, focally disrupted basal cell layers had several unique features: (1) significantly lower proliferation; (2) significantly lower p63 expression; (3) significantly higher apoptosis; and (4) significantly higher leukocyte infiltration and stromal reactions. Compared to their counterparts distant from focal disruptions or overlying non-disrupted basal cell layers, epithelial cells overlying focal basal cell layer disruptions showed the following unique features: (1) significantly higher proliferation; (2) significantly higher expression of cell cycle control-, cell growth-, and stem cell-related genes; and (3) physical continuity with adjacent invasive lesions. Together, these findings suggest that focal basal cell layer disruptions could substantially impact the molecular profile and biological presentations of the overlying epithelial cells. Based on these and other findings, we have proposed that prostate tumor invasion is triggered by a localized degeneration of aged or injured basal cells and the resultant auto-immunoreactions. Our hypothesized steps for prostate tumor invasion include the following: (1) due to inherited or environmental factors, some patients contained cell cycle control- and renewal-related defects in the basal cell population that cause elevated basal cell degenerations; (2) the degradation products of degenerated basal cells or diffusible molecules of the overlying epithelial cells attract leukocyte infiltration; (3) leukocytes discharge their digestive enzymes upon the direct physical contact, resulting in a focal disruption in the basal cell layer, which leads to several focal alterations: (a) a focal loss of tumor suppressors and paracrine inhibitory function; (b) a focal increase of the permeability for growth-required nutrients and oxygen; (c) a focal increase of growth factors; (d) direct physical contact between epithelial and stromal cells; and (e) the exposure of the overlying epithelial cells directly to the stromal tissue fluid. These alterations individually or collectively stimulate or favor a clonal proliferation and stromal invasion of tumor progenitor or stem cells. Our hypothesis differs from the traditional theories in several aspects, including the triggering factor for the initiation of tumor invasion, the stage of tumor invasion, the cellular origin of invasive lesions, the significance of immunoreactive and stromal cells, and the potential approaches for early detection, treatment, and prevention of invasion. Our hypothesis represents a novel in vivo model as to the cellular mechanism leading to prostate tumor invasion. If confirmed, it could lead to a new direction to search for more effective approaches to combat prostate cancer. It could also have an immediate impact on patient care through improved pathologic evaluation of prostate tumor biopsies. More importantly, our hypothesis might be applicable, and significantly impact the detection, treatment, and prevention of other epithelium-derived tumors.

Mechanisms of Disease: high-grade prostatic intraepithelial neoplasia and other proposed preneoplastic lesions in the prostate

High-grade prostatic intraepithelial neoplasia (HGPIN) is the most likely precursor of prostatic adenocarcinoma according to virtually all available evidence. This lesion is characterized by cellular proliferations within pre-existing ducts and acini, with nuclear and nucleolar enlargements similar to those seen in prostate cancer, although unlike cancer HGPIN retains a basal-cell layer. The recognition of HGPIN is clinically important because of the strong association between this disease and prostatic carcinoma. The predictive value for cancer of an initial diagnosis of HGPIN on needle biopsy has substantially declined, with values falling from 36% to 21%. A major factor contributing to this decline is related to increased use of needle biopsy core sampling, which has provided the means for many cancers associated with HGPIN to be detected on initial biopsy; repeat biopsy, even with good sampling, does not detect many additional cancers. Other possible findings in the prostate might indicate premalignant disease (low-grade prostatic intraepithelial neoplasia, atrophy, malignancy-associated changes, and atypical adenomatous hyperplasia or adenosis), but the data for these premalignant diseases are much less convincing than those for HGPIN.

The 3-dimensional structure of isolated and small foci of prostatic adenocarcinoma: the morphologic relationship between prostatic adenocarcinoma and prostatic intraepithelial neoplasia

BACKGROUND

Transitional histopathologic changes from high-grade prostatic intraepithelial neoplasia (HGPIN) into early prostatic adenocarcinoma (PAC) have not been well studied to date. To investigate the histogenesis of PAC, we examined isolated and small foci of PAC (ISPAC) found in prostatectomy specimens and the 3-dimensional structure of these foci.

DESIGN

Twelve consecutive radical prostatectomy specimens having ISPAC, performed for peripheral zone PAC (10 cases) and for transitional zone PAC (2 cases), of Gleason score were studied. One to 2 tissue blocks with representative sections were used.

RESULTS

Eight ISPAC, with Gleason score 3 + 3 had complete serial sections of the entire lesion. PAC consisted of continuous, tortuous and branching tubules and acini arising from benign ducts displaying: (a) HGPIN in 5 ISPAC and (b) no HGPIN in 3 ISAPC. At the junctions between benign epithelia with or without HGPIN and malignant epithelia, there were transitional lesions with HGPIN involving small ducts and acini.

CONCLUSIONS

PAC develops as a result of multiple outpouchings of the epithelium with formation of small ducts and acini showing cytologic atypia and gradual or abrupt loss of basal cells. Grade 3 ISPAC consists of a system of continuous duct pushing into the stroma. There is also evidence suggestive of HGPIN as being both a precursor lesion and an accompanying lesion of PAC.

My approach to intraductal lesions of the prostate gland

The morphologically heterogeneous (intra)ductal lesions of the prostate frequently present a diagnostic challenge, particularly when found within prostate needle biopsies. By current convention, all high-grade intra-acinar and intraductal neoplastic lesions of prostatic origin fall under the diagnostic umbrella term: prostatic intraepithelial neoplasm (PIN). Although a long-standing contentious issue, some lesions currently adhering to the diagnostic criteria of PIN may actually represent the intraductal spread of (generally high grade) invasive cancer. Illustrating this fact, the well-described ductal subtype of prostatic adenocarcinoma is frequently associated with conventional-type acinar adenocarcinoma, and has a tendency to propagate within adjacent intact prostatic ducts. Clearly, the misdiagnosis of lesions representing invasive disease as preinvasive has the potential for unfavourable clinical sequelae. As yet, however, many of these lesions have escaped the establishment of reliable morphologic criteria or immunohistochemical differentiation for diagnosis. By defining stringent architectural and cytonuclear features specific for each of these lesions, it may be feasible to separate potentially sinister lesions from the subset of traditional (preinvasive) PIN lesions with limited clinical urgency. This review discusses the (intra)ductal lesions of the prostate, along with their differential diagnoses. Given the current state of knowledge, a pragmatic approach to their effective reporting is outlined, taking into consideration the clinical implications, as well as current guidelines for treatment and follow-up.

High-grade prostatic intraepithelial neoplasia

High-grade prostatic intraepithelial neoplasia (PIN) is now accepted as the most likely preinvasive stage of adenocarcinoma, almost two decades after its first formal description. PIN has a high predictive value as a marker for adenocarcinoma, and its identification warrants repeat biopsy for concurrent or subsequent invasive carcinoma. The only method of detection is biopsy; PIN does not significantly elevate serum prostate-specific antigen (PSA) concentration or its derivatives and cannot be detected by current imaging techniques, including ultrasound. Most patients with PIN will develop carcinoma within 10 years. PIN is associated with progressive abnormalities of phenotype and genotype, which are similar to cancer rather than normal prostatic epithelium, indicating impairment of cell differentiation with advancing stages of prostatic carcinogenesis. Androgen deprivation therapy decreases the prevalence and extent of PIN, suggesting that this form of treatment may play a role in chemoprevention.

Contemporary pathology of prostate cancer

In less than 20 years since the introduction of serum PSA and the spring-loaded 18-gauge prostatic biopsy needle, pathologists have adjusted to the limited tissue requirements of narrow needle specimens to apply criteria for diagnosis and grading of prostate cancer, borrowing from lessons learned from radical prostatectomies. Substantial gains have been made during this period in the understanding of precancerous lesions, mimics of malignancy, the criteria for minimal cancer, variants of cancer, and treatment-induced changes. The light microscopic findings remain the criterion standard for diagnosis against which all new techniques should be measured. Numerous findings have proven to be of value, including simple quantitation of histopathologic features, cancer volume, perineural invasion, and others.

Alpha-methylacyl-CoA racemase (P504S) expression in evolving carcinomas within benign prostatic hyperplasia and in cancers of the transition zone

Carcinomas of the transition zone (TZ) constitute approximately 20% of all prostate cancers. The TZ is the site of origin of grade 1 and grade 2 cancers, the most well-differentiated of the Gleason grade tumors, as well as for benign prostatic hyperplasia (BPH). In this regard, grade 1 carcinoma has architectural features that closely mimic gland-rich BPH nodules. Although a relationship between cancers arising in this zone and BPH has been suspected, such an association remains undefined. To gain insight into the origin, development, and progression of cancers arising in the TZ, we used a highly specific rabbit monoclonal antibody (P504S) directed against alpha-methylacyl-CoA racemase (AMACR) to study the expression of the enzyme in 25 cases of evolving and fully developed carcinomas of this zone. AMACR has been proposed as a new molecular marker for prostate cancer, because the enzyme is reportedly overexpressed in high-grade dysplasias, also termed prostatic intraepithelial neoplasia, a purported precursor of prostatic carcinoma, and in all grades of prostatic carcinoma of the peripheral zone. Using P504S, P63, or antikeratin 34beta E12 antibodies, we found it possible to define areas of transition from hyperplasia to carcinoma in 6 BPH nodules. In 3 other cancer-containing BPH nodules, staining for AMCAR was observed in benign hyperplastic glands that were juxtaposed to carcinoma. Enzyme expression was also evident in 5 additional cases in which BPH was found adjacent to cancer. In contrast; AMACR was not visualized in any other BPH nodules that we studied. Thus, using the enzyme as a marker, we document for the first time that some carcinomas of the TZ arise from an AMCAR-positive transition lesion within a subset of BPH nodules. Moreover, the finding of enhanced AMACR expression in benign glands within cancer-containing nodules as well as in BPH lesions adjacent to carcinoma suggests that in some cases, up-regulation of the enzyme may precede morphological evidence of neoplastic transformation. AMACR was lightly expressed in transition lesions and grade 1 carcinomas but more strongly expressed in higher-grade TZ cancers, suggesting that enzyme expression is enhanced with progression in this zone. Because AMACR is involved in the beta oxidation of branched fatty acids and their derivatives, enhanced expression of the enzyme in evolving carcinomas in BPH nodules, as well as its up-regulation in juxtaposed morphologically benign glands and grade 1 carcinomas, suggests that increased utilization of fatty acids may play an important role in carcinoma development and progression in the TZ.

Precancerous lesions and conditions of the prostate: from morphological and biological characterization to chemoprevention

Prostatic intraepithelial neoplasia (PIN) is composed of dysplastic cells with a luminal cell phenotype, expressing the androgen receptor as well as prostate-specific antigen. PIN is characterized by progressive abnormalities of phenotype that are intermediate between normal prostatic epithelium and cancer, indicating impairment of cell differentiation and regulatory control with advancing stages of carcinogenesis. High-grade PIN is considered the most likely precursor of prostatic carcinoma, according to virtually all available evidence. Androgen deprivation decreases the prevalence and extent of PIN and the degree of capillary vascularization (e.g., angiogenesis) in the surrounding stroma via suppression of vascular endothelial growth factor production. Prostatic carcinoma is also likely to arise from precursor lesions other than high-grade PIN such as low-grade PIN, atypical adenomatous hyperplasia, malignancy-associated foci, and atrophy.

Chemoprevention for prostatic carcinoma: The role of flutamide in patients with prostatic intraepithelial neoplasia

High-grade prostatic intraepithelial neoplasia (HGPIN) is believed to be a precursor for prostatic adenocarcinoma. The prevalence of prostatic intraepithelial neoplasia (PIN) increases with advancing age. Autopsy studies suggest that PIN may precede the development of prostatic adenocarcinoma by up to 10 years. As such, HGPIN is believed to be a marker of increased risk. This provides a potential opportunity for chemoprevention. Flutamide is 1 agent with potential activity and limited side effects that may act to prevent or delay the onset of prostatic adenocarcinoma in men with HGPIN. A clinical trial is currently underway to assess the efficacy of flutamide.

Diagnosis of prostatic intraepithelial neoplasia: Prostate Working Group/consensus report

High-grade prostatic intraepithelial neoplasia (PIN) is the most likely precursor of prostatic carcinoma. PIN has a high predictive value as a marker for carcinoma, and its identification in biopsy specimens warrants repeat biopsy for concurrent or subsequent carcinoma. The only methods of detection are biopsy and transurethral resection; PIN does not significantly elevate serum PSA concentration or its derivatives, nor does it induce a palpable mass, and cannot be detected by ultrasound. Androgen deprivation therapy decreases the prevalence and extent of PIN, suggesting that this form of treatment may play a role in chemoprevention. Radiation therapy is also associated with a decreased incidence of PIN.

Vascular endothelial growth factor expression and capillary architecture in high-grade PIN and prostate cancer in untreated and androgen-ablated patients

BACKGROUND

Recent studies have demonstrated that angiogenesis is a potent prognostic indicator for patients with prostate cancer (PCa) and have pointed out that the evaluation of vascular endothelial growth factor (VEGF) is useful in assessing the angiogenic phenotype in PCa. The aim of the study was to investigate immunohistochemically the expression of VEGF and its correlation with the pattern of capillary architecture in prostate cancer and high-grade prostatic intraepithelial neoplasia (PIN), in untreated and androgen-ablated patients.

METHODS

Forty-five patients who underwent radical prostatectomy (RP) for localized prostate carcinoma were recruited for this study. The study population included two groups: 35 patients who did not receive chemo-, hormone, or radiation therapy before surgery, and 10 patients who were under complete androgen blockade (CAB) for 3 months at time of surgery. VEGF was examined by immunohistochemistry, and its tissue expression was compared with the pattern of capillary architecture evaluated by immunostaining the endothelial antigen CD34. The relationship of VEGF expression to chromogranin A-positive (e.g., neuroendocrine) cells was investigated.

RESULTS

In normal tissue, the intensity of the VEGF immunoreactivity in the cytoplasm of secretory cells ranged from negative to low. Very few basal cells stained for VEGF. All prostate cancer specimens stained positively, the intensity of the immunoreaction ranging from low to strong and being correlated with the Gleason score. Strongly positive VEGF immunoreactivity was detected in vascular endothelial cells and in stromal cells surrounding blood vessels. Two discrete immunostaining patterns were observed in high-grade PIN. VEGF expression of low-to-moderate intensity was defined as pattern A. The other, characterized by a strong cytoplasmic immunoreaction similar to that of poorly differentiated tumors, was defined as pattern B. The capillary architecture in high-grade PIN with pattern A was similar to the orderly vascular network seen in normal prostates, whereas in the pattern B it had the characteristics of microvessels usually seen in PCa. The degree of vascularization in the stroma adjacent to intensely VEGF-stained cells (neuroendocrine phenotype) was higher than that noted in association with secretory cells. CAB before surgery downregulated the expression of VEGF and decreased the degree of vascularization, except in the cell areas with neuroendocrine (NE) features.

CONCLUSIONS

Our immunohistochemical results indicate that significant levels of VEGF are present in prostate cancer and in a population of PIN lesions, expression being highest in association with NE cells. VEGF expression is downregulated by hormonal manipulation, except in the population of NE cells.

Morphological identification of the patterns of prostatic intraepithelial neoplasia and their importance

High grade prostatic intraepithelial neoplasia (PIN) is the most likely precursor of prostatic carcinoma. PIN has a high predictive value as a marker for carcinoma, and its identification in biopsy specimens warrants repeat biopsy for concurrent or subsequent carcinoma. The only methods of detection are biopsy and transurethral resection; PIN does not greatly raise the concentration of serum prostate specific antigen (PSA) or its derivatives, does not induce a palpable mass, and cannot be detected by ultrasound. Androgen deprivation decreases the prevalence and extent of PIN, suggesting that this form of treatment might play a role in chemoprevention. Radiotherapy is also associated with a decreased incidence of PIN.

Expression of pi-class glutathione S-transferase: two populations of high grade prostatic intraepithelial neoplasia with different relations to carcinoma

BACKGROUND/AIMS

Patients with high grade prostatic intraepithelial neoplasia of the transition zone appear to be at increased risk of developing prostatic carcinoma, although not to the same degree as patients with high grade prostatic intraepithelial neoplasia of the peripheral/central zone. Previous investigations have shown loss of expression of pi-class glutathione S-transferase (GST-pi; an enzyme that protects against electrophilic carcinogens) in prostatic carcinoma and in high grade prostatic intraepithelial neoplasia. The aim of this study was to compare the expression of GST-pi in high grade prostatic intraepithelial neoplasia of the transition zone with that in high grade prostatic intraepithelial neoplasia of the peripheral/central zone (that is, non-transition zone).

METHODS

Immunostaining with the anti-GST-pi antibody was performed on 20 high grade prostatic intraepithelial neoplasia samples of the transition zone, either isolated or associated with prostatic carcinoma (groups 1 and 2, respectively; 10 cases each) and on 20 high grade prostatic intraepithelial neoplasia samples of the non-transition zone, either isolated or associated with prostatic carcinoma (groups 3 and 4, respectively; 10 cases each). This study also included six samples of high grade prostatic intraepithelial neoplasia simultaneously present in the transition and non-transition zones and not associated with prostatic carcinoma (group 5). The presence of immunostaining, staining intensity, and the distribution of immunostaining were evaluated in the high grade prostatic intraepithelial neoplasia lesions and in the normal tissue and cancer areas.

RESULTS

The GST-pi antibody stained the cytoplasm of the cells lining the ducts and acini of normal prostate tissue. Staining was stronger and more diffuse in the basal cell layer than in the luminal (or secretory) cell layer. Immunohistochemical staining with anti-GST-pi antibodies failed to detect the enzyme in all prostatic carcinoma foci but one. Two patterns were detected in high grade prostatic intraepithelial neoplasia. One was represented by GST-pi staining similar to that of the normal tissue (pattern A). The other deviated from it and was characterised by absence of GST-pi expression in the secretory cells and abundant expression in scattered basal cells (pattern B). Pattern A staining was seen more frequently in the transition than in the non-transition zone. Pattern B staining was seen mainly in high grade prostatic intraepithelial neoplasia of non-transition zone associated with cancer.

CONCLUSIONS

The differential expression of GST-pi in the transition and non-transition zones indicates the existence of two populations with the morphological appearance of high grade prostatic intraepithelial neoplasia that might have different associations with carcinoma.

Prostatic intraepithelial neoplasia

High-grade prostatic intraepithelial neoplasia (PIN) is now accepted as the most likely pre-invasive stage of adenocarcinoma, a decade after its first formal description. PIN has a high predictive value as a marker for adenocarcinoma, and its identification warrants repeat biopsy for concurrent or subsequent invasive carcinoma. The only method of detection is biopsy; PIN does not significantly elevate serum prostate-specific antigen concentration or its derivatives and cannot be detected by ultrasound. Most studies suggest that most patients with PIN will develop carcinoma within 10 years. PIN is associated with progressive abnormalities of phenotype and genotype that are similar to cancer rather than normal prostatic epithelium, indicating impairment of cell differentiation with advancing stages of prostatic carcinogenesis. Androgen deprivation therapy decreases the prevalence and extent of PIN, suggesting that this form of treatment may play a role in chemoprevention.