Distribution of lipochrome pigment in the prostate gland: biological and diagnostic implications

Usefulness of GATA-3 as a marker of seminal epithelium in prostate biopsies

OBJECTIVES

The incidental presence of seminal vesicle epithelium in prostate needle biopsies is generally recognisable through routine microscopy. However, the biopsy can sometimes be erroneously interpreted as malignant due to its architectural and cytological characteristics, and immunohistochemistry can be useful for correctly identifying the biopsy. Our objective was to analyse the potential usefulness of GATA-3 as a marker of seminal epithelium.

MATERIAL AND METHODS

Through immunohistochemistry with a monoclonal anti-GATA-3 antibody (clone L50-823), we studied seminal vesicle sections from 20 prostatectomy specimens, 12 prostate needle biopsies that contained seminal vesicle tissue and 68 prostate biopsies without seminal vesicle epithelium, 36 of which showed adenocarcinoma.

RESULTS

Staining for GATA-3 was intense in the 20 seminal vesicles of the prostatectomy specimens and in the 12 prostate needle biopsies that contained seminal epithelium. In the 60 biopsies without a seminal vesicle, GATA-3 was positive in the prostate basal cells and even in the secretory cells (57 cases), although with less intensity in 55 of the cases. One of the 36 prostatic adenocarcinomas tested positive for GATA-3.

CONCLUSIONS

The intense immunohistochemical expression of GATA-3 in the seminal vesicle epithelium can help identify the epithelium in prostate biopsies. This marker is also positive in the basal cells of healthy prostates and, with less intensity, in the secretory cells. Positivity, weak or moderate, is observed on rare occasions in prostatic adenocarcinomas.

Seminal epithelium in prostate biopsy can mimic malignant and premalignant prostatic lesions

OBJECTIVES

In most prostate biopsies, the seminal epithelium is easily recognised because it meets characteristic histological criteria. However, some biopsies can mimic malignant or premalignant prostatic lesions. The aims of this study were to analyse the histological appearance of the biopsies that mimic adenocarcinomas or preneoplastic prostatic lesions, discuss the differential diagnosis and determine the frequency of seminal epithelia in prostate biopsies.

METHODS

We consecutively reviewed 500 prostate puncture biopsies obtained using the sextant method and selected those cases in which we observed seminal vesicle or ejaculatory duct epithelium. In the biopsies in which the seminal epithelium resembled malignant or premalignant lesions, immunohistochemical studies were conducted that included prostate-specific antigen and MUC6. The most important clinical data were recorded.

RESULTS

Thirty-six (7.2%) biopsies showed seminal epithelium, and 7 of them (1.4%) resembled various prostate lesions, including high-grade prostatic intraepithelial neoplasia, atypical acinar proliferations, adenocarcinomas with papillary patterns and poorly differentiated carcinoma. The seminal epithelium resembled prostate lesions when the lipofuscin deposit, the perinuclear vacuoles or the nuclear pseudoinclusions were inconspicuous or missing. Five of the 7 biopsies showed mild to moderate cellular atypia with small and hyperchromatic nuclei, and only 2 showed cellular pleomorphism. The patients were alive and asymptomatic after an average of 6 years of progression.

CONCLUSIONS

The seminal epithelium resembles prostatic intraepithelial neoplasia, atypical acinar proliferations and various types of prostatic adenocarcinomas in approximately 1.4% of prostate biopsies.

Activation of the long terminal repeat of human endogenous retrovirus K by melanoma-specific transcription factor MITF-M

The human and Old World primate genomes possess conserved endogenous retrovirus sequences that have been implicated in evolution, reproduction, and carcinogenesis. Human endogenous retrovirus (HERV)-K with 5'LTR-gag-pro-pol-env-rec/np9-3'LTR sequences represents the newest retrovirus family that integrated into the human genome 1 to 5 million years ago. Although a high-level expression of HERV-K in melanomas, breast cancers, and teratocarcinomas has been demonstrated, the mechanism of the lineage-specific activation of the long terminal repeat (LTR) remains obscure. We studied chromosomal HERV-K expression in MeWo melanoma cells in comparison with the basal expression in human embryonic kidney 293 (HEK293) cells. Cloned LTR of HERV-K (HML-2.HOM) was also characterized by mutation and transactivation experiments. We detected multiple transcriptional initiator (Inr) sites in the LTR by rapid amplification of complementary DNA ends (5' RACE). HEK293 and MeWo showed different Inr usage. The most potent Inr was associated with a TATA box and three binding motifs of microphthalmia-associated transcription factor (MITF). Both chromosomal HERV-K expression and the cloned LTR function were strongly activated in HEK293 by transfection with MITF-M, a melanocyte/melanoma-specific isoform of MITF. Coexpression of MITF and the HERV-K core antigen was detected in retinal pigmented epithelium by an immunofluorescence analysis. Although malignant melanoma lines MeWo, G361, and SK-MEL-28 showed enhanced HERV-K transcription compared with normal melanocytes, the level of MITF-M messenger RNA persisted from normal to transformed melanocytes. Thus, MITF-M may be a prerequisite for the pigmented cell lineage-specific function of HERV-K LTR, leading to the high-level expression in malignant melanomas.

Primary prostatic central zone adenocarcinoma

The central zone (CZ) of the prostate is embryologically, anatomically, and histologically distinct. High-grade prostatic intraepithelial neoplasia (HGPIN) and prostatic adenocarcinoma (PAC) are encountered in the CZ, but have not been well studied. Non-CZ PAC that spread into the CZ can mimic CZ PAC. We reviewed 300 consecutive radical prostatectomies performed for PAC to identify cases showing PAC and HGPIN in the CZ. There were nine PAC (3%) localized predominantly in the CZ, presenting as a single tumor nodule (8/9) and associated with 4.5+/-1.1 foci HGPIN in the CZ and with only 1.7+/-0.5 foci in the PZ. Of the 291 non-CZ PAC, 24 cases showed satellite tumor nodules in the CZ, and 92 cases demonstrated secondary contiguous spread to the CZ. As compared to the non-CZ PAC, CZ PAC tended to have lower tumor volume, but had higher Gleason scores (8.10+/-0.6 vs. 6.30+/-0.7, p<0.05), as well as a higher incidence of a ductal carcinoma component (6/9), higher rates of capsular penetration, positive resection margins (4/9), and seminal vesicle spread (2/9). The CZ HGPIN associated with CZ PAC demonstrated cells with prominent nucleoli and formed either slender papillary structures or cribriform/solid patterns. The correlating positive biopsy cores were from the mid portion or from base of prostate and contained foci of HGPIN in 4/7 cases. The CZ PAC is characteristically accompanied by more foci of HGPIN in the CZ than in non-CZ and is associated with high grade and high stage. Preoperative diagnosis of CZ PAC can be suspected due to the histopathological features in the biopsy and is important to improve the free surgical resection rate.

Lipofuscin pigment can be used as a prognostic marker in prostatic adenocarcinoma

Lipofuscin, known as the "wear and tear" pigment, is seen in cells undergoing regressive changes, the seminal vesicles and the ejaculatory ducts. It is also present in prostatic adenocarcinoma. The purpose of this study is to evaluate the prognostic significance of lipofuscin in prostatic adenocarcinoma. Lipofuscin was evaluated in 736 hematoxylin-eosin-stained slides from 60 conventional and whole-mounted consecutive radical prostatectomies from December 1996 to February 2002. The adenocarcinoma cases were divided into lipofuscin-positive group and lipofuscin-negative group. The Gleason score and pathologic stage were compared between the 2 groups. Percentage of cells positive for p53 and MIB-1 was also compared. Lipofuscin pigment was found in 17 (31%) of 60 prostatic adenocarcinomas as random, sparse, fine, yellow-brown intracytoplasmic granules staining positive for cathepsin D and negative for S-100 protein. Using logistic regression to exclude age as a confounding factor, lower Gleason scores and pathologic stages were demonstrated in the lipofuscin-positive group. There was also a significant difference between the 2 groups in tumor volume, degree of capsular invasion, and positive margins. The difference in seminal vesicle invasion and vascular invasion between the 2 groups was not statistically significant. Lipofuscin in prostatic adenocarcinoma correlates with both lower Gleason score and pathologic stage. Lipofuscin probably indicates slow cellular turnover as suggested by the low proliferation rate and p53 expression. The value of lipofuscin in biopsy as a predictor separating aggressive from indolent disease needs further investigation.

Differential protein expression in anatomical zones of the prostate

The prostate has three anatomical zones: the peripheral (PZ), the transition (TZ), and the central (CZ) zone. It is proposed that the CZ may be of mesodermal origin, whereas the other two are of endodermal origin. Proteome patterns in the zones were characterized to test for differences. Cells were scraped from macroscopically normal areas of PZ, TZ, and CZ in radical prostatectomy specimens. After exclusion of samples with cancer or prostatic intraepithelial neoplasia, 18 cases remained for analysis. Cells were collected in a medium with protease inhibitors, and the protein material was prepared for two-dimensional gel electrophoresis. The proteins in spots that differed quantitatively between regions were identified via mass spectrometric fingerprinting of tryptic fragments and selected tandem mass spectrometry sequence analysis. Ten proteins with significant zonal differential expression were identified, eight with underexpression in the CZ versus the PZ and the TZ (arginase II, ATP synthase, cytokeratin 8, lamin A/C, peroxiredoxin 4, protein disulfide isomerase A3, tropomyosin, and vimentin), and two with overexpression in the CZ (peroxiredoxin 2 and creatine kinase B). The PZ and TZ, although differing in terms of incidence of cancer and hyperplasia, have epithelium with highly similar major protein expression profiles. However, the protein profile of the CZ differs from that of the other regions, suggesting functional differences.

Benign mimickers of prostatic adenocarcinoma

The diagnosis of prostatic adenocarcinoma, especially when present in small amounts, is often challenging. Before making a diagnosis of carcinoma, it is prudent for the pathologist to consider the various benign patterns and processes that can simulate prostatic adenocarcinoma. A useful method of classifying benign mimickers is in relationship to the major growth patterns depicted in the classical Gleason diagram. The four major patterns are small gland, large gland, fused gland and solid. Most mimickers fit within the small gland category and the most common ones giving rise to false-positive cancer diagnosis are atrophy, post-atrophic hyperplasia, atypical adenomatous hyperplasia and seminal vesicle-type tissue. A number of other histoanatomic structures such as Cowper's gland, verumontanum mucosal glands, mesonephric glands and paraganglionic tissue may be confused with adenocarcinoma. Additionally, metaplastic and hyperplastic processes within the prostate may be confused with adenocarcinoma. Furthermore, inflammatory processes including granulomatous prostatitis, xanthogranulomatous prostatitis and malakoplakia may simulate high-grade adenocarcinoma. Atypical adenomatous hyperplasia (adenosis), a putative precursor of transition zone adenocarcinoma, has overlapping features with low-grade adenocarcinoma and may cause problems in differential diagnosis, especially in the needle biopsy setting. The pathologist's awareness of the vast array of benign mimickers is important in the systematic approach to the diagnosis of prostatic adenocarcinoma. Knowledge of these patterns on routine microscopy coupled with the prudent use of immunohistochemistry will lead to a correct diagnosis and avert a false-positive cancer interpretation.

Cytology of the central zone of the prostate

The prostate has three anatomical regions: the peripheral, transition, and central zones (CZ). The CZ has distinct histological features, but its cytological morphology has not been described. This study was done on surgical specimens to ensure that samples were representative of the CZ, and that no prostatic intraepithelial neoplasia (PIN) or cancer contaminated the smears. An incision was made in the CZ of 51 prostatectomy specimens, and cells were scraped from cut surfaces. After exclusion of samples contaminated by PIN or cancer or with poor cell yield, 39 Giemsa-stained smears remained for analysis. Large branching epithelial sheets with geographic architecture and crowded nuclei were seen in 97% of smears. Epithelial clusters with elongated palisaded nuclei were identified in 80% of cases, but were always a minor component. Visible nucleoli (97%), cytoplasmic vacuoles (97%), and smooth muscle cells in the background (95%) were common. Blue-green cytoplasmic granules resembling seminal vesicle pigment were seen in 97%. Magenta-colored cytoplasmic pigment, similar to granules seen in other regions of the prostate, was found in 74%. Recognition of CZ epithelium as a benign constituent of prostate cytology is important because elongated cells, crowded nuclei, and visible nucleoli may otherwise be misinterpreted as PIN or cancer.

MUC6 is a marker of seminal vesicle-ejaculatory duct epithelium and is useful for the differential diagnosis with prostate adenocarcinoma

The diagnosis of prostate adenocarcinoma is usually made on needle biopsies. Numerous benign lesions may mimic malignancy, especially when the focus of carcinoma is limited. The presence of seminal vesicle-ejaculatory duct epithelium on prostate biopsy is not rare and could cause confusion with adenocarcinoma. Lipochrome pigments are frequently encountered in seminal vesicle-ejaculatory duct but may be also seen in prostate adenocarcinoma. Prostate specific antigen immunostaining in difficult cases is sometimes used, but high-grade adenocarcinomas may be negative. In one previous report, MUC6 was found to be expressed in seminal vesicle but not in normal prostate. MUC6 belongs to the family of human mucin genes. So we investigated herein the immunohistochemical expression of MUC6 in prostate adenocarcinomas and seminal vesicle-ejaculatory duct. We have tested 30 prostate adenocarcinomas of various grade, 10 normal seminal vesicles, and 10 prostate adenocarcinomas invading the seminal vesicles. The tissues were fixed in 10% buffered formalin and embedded in paraffin. Immunohistochemistry was performed using the avidin-biotin-peroxidase complex technique. All adenocarcinomas and normal prostate structures tested were negative. In contrast, all seminal vesicles were diffusely immunostained with MUC6 antibody. We concluded that MUC6 is a valuable marker of seminal vesicle-ejaculatory duct and is useful for the differential diagnosis with prostate adenocarcinoma.

[Prostatic blue nevus. Terminology standardization of prostatic pigmented lesions]

We expose a new case of prostatic blue nevus. The existing confusion in the terminology of the prostate pigmentarias injuries in reviewed literature is commented and we concluded, based on the opinion of most of authors, with a possible unification of creteries the same ones.

Prostate-specific antigen expression and lipochrome pigment granules in the differential diagnosis of prostatic adenocarcinoma versus seminal vesicle-ejaculatory duct epithelium

BACKGROUND

Lipochrome pigment granules (LPGs) and prostate-specific antigen (PSA) localization have been cited as helpful adjuncts in differentiating atypical histologic patterns of seminal vesicle-ejaculatory duct (SVED) from prostatic adenocarcinoma. However, LPGs have been described in both benign and neoplastic prostatic acini, and PSA expression within the intraprostatic SVED has not been fully explored.

DESIGN

Fifty radical prostatectomy specimens were studied for LPGs and 9 cases for PSA expression.

RESULTS

Two morphologic types of LPGs (type 1 and type 2) were observed. The reproducibility in classifying LPGs was evaluated by kappa statistics, which demonstrated a strong agreement between 4 observers. Type 1 was restricted to SVED in all 50 specimens. Type 2 was subclassified into 2A and 2B. Type 2 LPGs were observed in prostatic acini of different zones, high-grade prostatic intraepithelial neoplasia, prostatic adenocarcinoma, and occasionally with type 1 LPG in SVED. Focal reactivity for PSA in the distal portion of SVED near urethra was noted in 1 of 9 cases.

CONCLUSION

Awareness about morphologic differences between the 2 types of LPGs could help to avoid a potential diagnostic pitfall of misinterpreting SVED epithelium for adenocarcinoma. Caution is recommended in interpreting PSA expression, since rare focal PSA reactivity was observed in the distal SVED.