The utility of Ki-67 expression in the differential diagnosis of prostatic intraepithelial neoplasia and ductal adenocarcinoma

Biopsy sampling and histopathological markers for diagnosis of prostate cancer

Prostate cancer is one of the most common malignant tumors and a leading cause of cancer-related morbidity and mortality. Irrespective of the method that allows for risk stratification of prostate cancer suspects, diagnosis relies on tissue sampling through prostate biopsy and subsequent histopathological evaluation. This provides critical information about disease aggressiveness, which is required for adequate patient management. Prostate biopsy methods have significantly evolved over the years, including the definition of indications, sampling schemes and use of imaging techniques (ultrasound and MRI) that allow for more accurate tissue sampling. In response to the challenges emerging from more precise collection of minute prostate tissue samples for analysis, histopathological assessment should include not only the observation of routinely stained sections, but also, and increasingly so, a series of ancillary techniques, especially immunohistochemistry, which increment the accuracy of prostate cancer diagnosis and may provide relevant information to guide patient management.

Immunohistochemical profile of ductal adenocarcinoma of the prostate

Ductal adenocarcinoma of the prostate (DAC) is considered to be an aggressive subtype of prostate cancer with greater risk of progression than acinar adenocarcinoma (AC). It has been debated whether DAC is a distinct subtype or a morphological variant of AC. Our aim was to examine the protein expression of DAC and to compare the results with AC. A tissue microarray was constructed from 60 DAC and 46 AC matched by Gleason score. The slides were stained for 28 immunomarkers (estrogen, progesterone and androgen receptor, prolactin, PSA, prostein, PSMA, PSAP, CDX2, lysozyme, villin, monoclonal CEA, CK7, CK20, HMWCK, p63, p504s, c-myc, EGFR, Ki-67, p16, p21, p27, p53, PTEN, ERG, PAX-2, and PAX-8). HMWCK was positive in 8.5 % of DAC, but negative in all cases of AC (p = 0.045). p16 was positive in 53.3 % of DAC and in 26.1 % of AC (p = 0.005). p53 was positive in 42.4 % of DAC and 26.7 % of AC (p = 0.031). A distinct patchy positivity of CK20 was seen in 23.7 % of DAC, and this pattern was also seen in 9.1 % of AC (p = 0.047). Villin was positive in 3.4 % of DAC while expression was negative in AC. Ki-67 labeling index was significantly higher in DAC than in AC (mean 9.2 % [95 % CI 6.4-12.0] and 2.6 % [1.9-3.4], p < 0.001). While there is some overlap in the immunohistochemical expression of DAC and AC, the differences between these two morphotypes of prostatic carcinoma are consistent with DAC having a more aggressive phenotype than AC.

JPEG2000 for automated quantification of immunohistochemically stained cell nuclei: a comparative study with standard JPEG format

The Joint Photographic Experts Group (JPEG) standard format is one of the most widely used in image compression technologies. More recently, JPEG2000 format has emerged as a state-of-the-art technology that provides substantial improvements in picture quality at higher compression ratios. However, there has been no attempt to date to determine which of the two compression formats produces less variability in the automated evaluation of immunohistochemically stained digital images in agreement with their compression rates and complexity degrees. The evaluation of Ki67 and FOXP3 immunohistochemical nuclear markers was performed in a total of 329 digital images: 47 were captured in uncompressed Tagged Image File Format (TIFF), 141 were converted to three JPEG compressed formats (47 each with 1:3, 1:23 and 1:46 compression) and 141 were converted to three JPEG2000 compressed formats (47 each with 1:3, 1:23 and 1:46 compression). The count differences between images in TIFF versus JPEG formats were compared with those obtained between images in TIFF versus JPEG2000 formats at the three levels of compression. It was found that, using JPEG2000 compression, the results of the stained nuclei count are close enough to the results obtained with uncompressed images, especially in highly complex images at minimum and medium compression. Otherwise, in images of low complexity, JPEG and JPEG2000 had similar count efficiency to that of the original TIFF images at all compression levels. These data suggest that JPEG2000 could give rise to an efficient means of storage, reducing file size and storage capacity, without compromise on the immunohistochemical analytical quality.

Estudo citofotométrico da expressão dos marcadores tumorais Ki-67 e CD34 no adenocarcinoma de próstata

OBJETIVO: Quantificar a porcentagem da imunomarcação no índice de marcagem e densidade óptica do Ki-67 e CD34 no adenocarcinoma de próstata e compará-las entre si. MÉTODOS: Foram estudados, através de imunoistoquímica, o Ki-67 e o CD34 em 34 casos de adenocarcinoma de próstata provenientes de prostatectomia radical no período de 2000 a 2005 realizado no Hospital Regional do Gama em Brasília. Estes marcadores foram quantificados através do software SAMBA 4000 ® Sistema de Análise Microscópica de Busca Automática e do software IMMUNO® para análise das variáveis índice de marcagem e densidade óptica. Para avaliação da associação entre as expressões do marcador, foi estimado o coeficiente de correlação de Spearman. Para a comparação do tipo de lesão, foi usado o teste t de Student em amostras pareadas e não paramétrico de Wilcoxon. RESULTADOS: Dos 34 blocos que foram para leitura dos marcadores tumorais, 15 marcaram expressão com Ki-67, 34 com CD34 e 14 com ambos os marcadores. O índice de marcagem do CD34 teve valor mediano de 72,72%, valor mínimo 5,14% e valor máximo 88,81%. O índice de marcagem do Ki-67 teve mediana de 73,78%, mínimo de 16,87% e máximo de 87,47%. A densidade óptica do CD34 teve mediana de 48,33, mínimo de 35,65 e máximo de 85,86. Na densidade óptica do Ki-67 o valor da mediana foi 40,03 sendo a mínima de 21,53 e a máxima de 52,43. CONCLUSÃO: A expressão citofotométrica do Ki-67 teve índice médio de marcação de 64,04% e o CD34 de 61,64%. A expressão citofotométrica da densidade óptica média do Ki-67 foi de 39,49 e no CD34 de 53,69. Há diferença significativa entre a imunomarcação do Ki-67 e CD34 em relação à densidade óptica (p=0,025), não havendo diferença significativa no índice de marcagem (p=0,470).

Gene expression profiles of ductal versus acinar adenocarcinoma of the prostate

Ductal adenocarcinoma is an uncommon variant of prostatic adenocarcinoma with a generally more aggressive clinical course than usual acinar adenocarcinoma. However, the molecular distinction between ductal and acinar adenocarcinomas is not well characterized. The aim of this investigation was to evaluate the relatedness of ductal versus acinar prostatic adenocarcinoma by comparative gene expression profiling. Archived, de-identified, snap frozen tumor tissue from 5 ductal adenocarcinomas, 3 mixed ductal-acinar adenocarcinomas, and 11 acinar adenocarcinomas cases were analyzed. All cases of acinar and ductal adenocarcinomas were matched by Gleason grade. RNA from whole tissue sections of the 5 ductal and 11 acinar adenocarcinomas cases were subjected to gene expression profiling on Affymetrix U133Plus2 microarrays. Independently, laser-capture microdissection was also performed on the three mixed ductal-acinar cases and five pure acinar cases to isolate homogeneous populations of ductal and acinar carcinoma cells from the same tumor. Seven of these laser-capture microdissected samples (three ductal and four acinar cell populations) were similarly analyzed on U133Plus2 arrays. Analysis of data from whole sections of ductal and acinar carcinomas identified only 25 gene transcripts whose expression was significantly and at least two-fold different between ductal and acinar adenocarcinomas. A similar analysis of microdissected cell populations identified 10 transcripts, including the prolactin receptor, with more significant differences in expression of 5- to 27-fold between ductal and acinar adenocarcinomas cells. Overexpression of prolactin receptor protein in ductal versus acinar adenocarcinoma was confirmed by immunohistochemistry in an independent set of tumors. We conclude that ductal and acinar adenocarcinomas of the prostate are strikingly similar at the level of gene expression. However, several of the genes identified in this study, including the prolactin receptor, represent targets for further investigations on the molecular basis for histomorphological and clinical behavioral differences between acinar and ductal adenocarcinomas.

Prostatic ductal adenocarcinoma presenting as a urethral polyp: a clinicopathological study of eight cases of a lesion with the potential to be misdiagnosed as a benign prostatic urethral polyp

AIMS

Centrally located prostatic ductal adenocarcinoma can present as a single urethral polyp mimicking a benign polyp. Such lesions have not been formally studied.

METHODS AND RESULTS

Clinicopathological and immunohistochemical findings of eight cases were analysed. Patients (mean age 76 years) presented with urinary symptoms and haematuria. Mean serum prostate specific antigen (PSA) was 7.01 ng/mL (range 1.04-21). Single small polyps were seen on cystourethroscopy with a clinical diagnosis of benign polyps. The most common architectural patterns were cribriform and papillary. Five cases had mild cytological atypia, three of which were initially diagnosed as benign prostatic urethral polyps. All cases were positive for PSA and 34betaE12. Seven cases tested were positive for AMACR (a-methylacyl-CoA racemase), p63 and cytokeratin (CK) 7 and 70% for CK20. Proliferative activity defined as Ki-67 labelling index was high (mean 26%, range 20-35%). Adenocarcinoma, predominantly ductal, was found in other specimens in four patients.

CONCLUSIONS

Centrally located prostatic ductal adenocarcinoma has the propensity to mimic benign urethral polyps clinically and histopathologically. Basal cell immunostaining may not help with this distinction but AMACR is useful. Prominent glandular complexity including cribriform patterns, nuclear pseudostratification, at least mild atypia and a high Ki-67 index distinguish these lesions from prostatic urethral polyps.

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.

Immunohistochemistry in diagnostic surgical pathology of the prostate

Immunohistochemistry (IHC) can play an important role in diagnostic surgical pathology of the prostate. Basal cell markers, such as the 34betaE12 antibody and antibodies directed against cytokeratin 5 and 6 or p63, are very useful for demonstration of basal cells as their presence argues against a diagnosis of invasive prostatic carcinoma (PC). However, several benign mimickers of PC, including atrophy, atypical adenomatous hyperplasia (AAH), nephrogenic adenoma, and mesonephric hyperplasia, can stain negatively with these markers, and thus, a negative basal cell marker immunostain alone does not exclude a diagnosis of benignancy. Although there are examples in the literature of high grade PC that stain focally with some of the basal cell markers, these cases are usually readily diagnosed based on H&E appearances and are unlikely to be confused with these benign mimickers. Alpha-methylacyl-coenzyme-A racemase (AMACR) is a sensitive marker of PC (except for a few uncommon variants: atrophic, foamy gland, and pseudohyperplastic variants), and its detection by immunohistochemical staining in atypical prostatic lesions can be very useful in confirming an impression of adenocarcinoma. AMACR expression can also be identified in high grade prostatic intraepithelial neoplasia (PIN), prostatic atrophy, AAH, and benign prostatic glands, and accordingly, a diagnosis of PC should not be based solely on a positive AMACR immunostain, especially when the luminal staining is weak and/or noncircumferential. The use of AMACR/basal cell antibody cocktails has been found to greatly facilitate the distinction between PC and its benign mimickers, especially when only limited tissue is available for staining. Prostate specific antigen (PSA) and prostate specific acid phosphatase (PSAP) are both quite sensitive and fairly specific markers of PC (there are a few nonprostatic tumors that can express one or both), and are both very helpful in establishing or confirming the diagnosis of PC when the differential diagnosis includes other tumors that can involve the prostate such as urinary bladder urothelial carcinoma. 34betaE12, p63, thrombomodulin, and uroplakin III are additional urothelial associated markers useful in this differential diagnosis. CDX2 and villin are useful markers to diagnostically separate colonic adenocarcinoma from PC. AMACR positivity and negative basal cell marker reactions are useful to confirm the presence of residual PC after hormonal or radiation therapy. Pan-cytokeratin, PSA, and PSAP can also highlight subtle infiltrates of PC with hormonal or radiation therapy effect. PSA and PSAP immunohistochemical stains are valuable in confirming metastatic carcinoma as being of prostatic origin and should always be utilized in the diagnostic evaluation of metastatic adenocarcinoma of unknown primary origin in males.