Digital image analysis of proliferative index: two distinct populations of high-grade prostatic intraepithelial neoplasia in close proximity to adenocarcinoma of the prostate

Natural history of prostatic carcinoma: the pathologist's perspective

The stem (basal) cells of prostate acini are considered the origin of prostate cancer. Between these cells and the final secretory cells, different intermediate or transit cells can be observed, and every one of them can evolve into malignant cells, explaining the biological variability of prostatic cancer. The exact changes between normal gland and prostatic intraepithelial neoplasia (PIN) are not yet known, but a post-inflammatory atrophy lesion is being studied in this respect. The PIN lesion is considered the pre-invasive change of prostatic cancer and its presence in needle biopsy is clinically used for follow-up of the patient. The progressive knowledge of the stromal invasion in prostate cancer (loss of some cell-cell adhesion molecules and expression of others) can be correlated with the Gleason grading system, and the molecular changes in the progression to androgen-independent carcinoma can be used as a prognostic marker in conjunction with the classical pathological markers.

p16 Is upregulated in proliferative inflammatory atrophy of the prostate

BACKGROUND

Proliferative inflammatory atrophy (PIA) of the prostate is a common histological finding that has been postulated to be associated with prostate cancer. We examine PIA lesions for the expression of p16/CDKN2, a cyclin-dependent kinase inhibitor frequently altered in prostate cancer.

METHODS

Within tissues from two independent patient populations ("Test Set" and "Validation Set") undergoing radical prostatectomy, PIA lesions were identified and subjected to immunohistochemical staining for p16. Atrophic epithelial cells and regional normal epithelium were scored for the extent of p16 staining. In the Test Set, staining was also performed for the proliferation marker Ki-67. Double label immunofluorescence was employed to co-localize staining for p16 and Ki-67.

RESULTS

p16 expression was elevated in PIA in both data sets compared to normal epithelium (mean percent of cells staining positive in PIA = 11.1%-16.2%; mean percent of cells staining positive in normal = 0.6%-1.3%) (P = 0.0001). As expected from prior studies, the mean Ki-67 index was higher in PIA lesions (mean 8.2% staining positive) versus normal epithelium (mean 1.9% staining positive) (P = 0.0001), and the extent of staining for p16 correlated with Ki-67 (r = 0.7, P < 0.0001). However, co-localization immunofluorescent studies did not demonstrate staining for nuclear p16 and Ki-67 in the same cells.

CONCLUSIONS

Increased p16 expression accompanies increased cell proliferation in PIA lesions of the prostate. Yet, on the individual cell level, the upregulation of p16 in PIA lesions appears to represent a non-proliferative stress response, possibly to oxidative damage.

Incidentally detected prostate cancer in cystoprostatectomies: pathological and morphometric comparison with clinically detected cancer in totally embedded specimens

There are limited data regarding the pathological features of incidentally detected prostate cancer. Examination of cystoprostatectomy specimens obtained during bladder cancer treatment affords a unique opportunity to examine incidentally detected prostate cancer and determine its relationship with clinically detected prostate cancer obtained during radical prostatectomy. We compared the pathological findings of incidentally detected prostate cancer in 132 consecutive cystoprostatectomy specimens from patients treated for bladder cancer with a consecutive series of 228 radical prostatectomy specimens from patients treated for prostate cancer. All specimens were totally embedded and whole-mounted. Karyometry was evaluated in select subsets of patients from the study groups. Incidentally detected cancer was found in 42% of cystoprostatectomy specimens, and the cancers were of lower Gleason score and lower pathological stage with fewer positive surgical margins than in clinically detected cancers in age-matched radical prostatectomies. High-grade prostatic intraepithelial neoplasia (PIN) was present in 82% of radical prostatectomy specimens, in 70% of cystoprostatectomies with incidentally detected prostate cancer, and in 54% of cystoprostatectomies without prostate cancer. Mean nuclear and nucleolar area was lower in incidentally detected cancer and PIN when compared with clinically detected cancer and PIN, respectively, similar to the results with proliferative indices. We conclude that incidentally detected cancer is less aggressive than clinically detected cancer.

Karyometry detects subvisual differences in chromatin organization state between cribriform and flat high-grade prostatic intraepithelial neoplasia

This digital texture analysis-based study evaluates the chromatin organization state in flat and cribriform high-grade prostatic intraepithelial neoplasia (PIN), in the adjacent normal looking secretory epithelium and in the co-occurring adenocarcinoma. Digital texture analysis (karyometry) was carried out on hematoxylin and eosin-stained sections from 24 radical prostatectomy specimens with high-grade PIN (12 with flat and 12 with cribriform architectural pattern, respectively) and cancer. Quantification was also conducted on the normal looking secretory epithelium. Discriminant analysis and the nonsupervised learning algorithm P-index were used to identify suitable subsets of features useful for the discrimination and classification of pathological groups and to explore multivariate data structure in the pathological subgroups. The average nuclear abnormality increases monotonically from the histologically normal appearing secretory epithelium to high-grade PIN and to adenocarcinoma. The nuclei from the so-called perimeter compartment of the flat high-grade PIN lesions show a higher nuclear abnormality compared to the nuclei of the cribriform high-grade PINs. Discriminant analysis shows that flat and cribriform high-grade PINs fall into two populations. Processing by the nonsupervised learning algorithm P-index revealed the existence of three well-defined, distinct subpopulations of nuclei of different chromatin phenotype. In the flat high-grade PIN lesions the proportions of nuclei in the three subpopulations are 16.5% (low abnormality), 25.0% (mid abnormality) and 58.5% (high abnormality), respectively. In the cribriform high-grade PIN lesions, 100% of the nuclei are in the mid-abnormality subpopulation. These differences are also discernible in the co-occurring adenocarcinoma and the histologically normal appearing secretory epithelium. To conclude, karyometry and statistical analysis detect the existence of distinct cell subpopulations of different chromatin packaging and phenotype, with the nuclei from the flat high-grade PIN lesions, adjacent normal looking epithelium and co-occurring adenocarcinoma expressing a greater nuclear abnormality than in the specimens with cribriform high-grade 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.

An image analysis strategy to determine the distribution of cell types in spleen sections

An image analysis strategy was designed to objectively determine distribution patterns of cell types in spleen sections. The strategy was applied to rat spleen cryostat sections that were strained immunohistochemically by means of monoclonal antibodies against different populations of lymphocytes and macrophages. The strategy revealed three segments of the spleen beginning in the middle of a central arteriole and ending within the red pulp. In each of these segments, three consecutive zones were established: the white pulp, the marginal zone, and the red pulp. In each tissue section, three segments were selected starting in two different arterioles. Consequently, six segments were analysed in each section. Special software was used to calculate percentages of positive staining in all zones in each segment. Image analysis data for each monoclonal antibody tested correlated closely with microscopical observations. The proposed strategy allows objective quantification of lymphocyte and macrophage populations and their distribution patterns. It is an useful tool for studying imbalances in cell populations in the spleen due to immune challenges.