Prostate

Prostate

Function

The vagina has an environment which is slightly acidic, with approximately a pH of 4, this is to protect against pathogens. Sperm however, are acid-sensitive, thus their environment, semen, is alkaline. Due to this, any ejaculate abolishes the vaginas protective acidity for many hours after it's entry, this is to ensure survival of the sperm. Seminal vesicle secretions are rich in fructose, as this is a primary energy source for sperm, and also rich in prostaglandins and proteins which promote semen clotting in the vagina. These secretions are also rich in Ca2+, zinc, citric acid, acid phosphatase, albumin and prostatic specific Ag (PSA). PSA has the ability to reverse the clotting enzyme affect from seminal vesicle fluid. he enzyme has the ability to make ejaculate gel and "glue" in place in the female cervix. Sperm will remain within this gel, until the PSA enzyme dissolves the clot and allows sperm to swim into the uterus.  

The exocrine gland is the size of a walnut, and weights approximately 20 grams. Within the adult prostatic parenchyma may be divided into 4 biologically and anatomically distinct zones or regions:

1. Peripheral
2. Central
3. Transitional zones
4. Region of the anterior fibromuscular stroma  

These are important as different types of proliferative lesions may arise in each region. For example, most hyperplasias arise in the transitional zone, and most carcinomas originate in the peripheral zone. 

This is important to mention in the exam. Try and draw it in the exams if needed (not a rude picture though!).

Figure 1. Picture provided by Roy Stewarts "Prostate" lecture presentation.

Histology

This is very important to include:

It is very important that the normal histology is known, as this is the main way to diagnose benign vs malignant tumours. This is also used in the grading of prostate cancer. Essentially, the prostate is a gland composed of tubular glands which have 2 layers of cells:

• Basal cuboidal layer: rests of a basement membrane
• Inner columnar luminal layer

The glands can be rounded or have papillary type (nipple like) projections. This can be useful diagnostically. The rest of the gland is background stromal cells consisting of fibro-muscular tissue, which has an influence of the glandular tissue itself, and not just inert background material. 

Normal histology and immunohistochemistry

The basal layer is positive for high molecular weight cytokeratins and the mouse antibody cocktail anti-cytokeratin 34bE12 reacts with cytokeratins 1,5,10 and 14. P63 is also positive, and it has been shown that without P63, mice do not develop a prostate, thus a cocktail of 34bE12 and P63 is a good marker, in order to pick up all of the basal cells. Remembering the names of this will give you more marks. Corpora amylacea - normally found in normal prostate. 

Benign prostatic hyperplasia (BHP)

Major theories attempting to explain the aetiology of pathological phase BPH include:

1. Dihydrotestosterone (DIT) hypothesis: this is a shift in prostatic androgen metabolism that occurs due to age, leading to abnormal accumulations of DHT, producing an enlarged prostate. 
2. Embryonic reawakening theory: a reawakening of the embryonic induction potential of prostatic stroma - a change in the prostatic stromal-epithelial interaction that occurs alongside ageing, leading to an a promoting effect on prostatic growth.
3. Stem cell theory: featuring an increase in the total prostatic stem cell numbers and/or clonal expansion of stem cells into amplifying and moving cells which occurs with ageing. 
4. Inflammatory theory: Prostatic inflammation may contribute to the growth of the prostate, due to the inducing of cellular growth because of the presence of inflammatory markers and agents which have growth stimulating abilities. 

BHP involves the enlargement of glandular and stromal tissue, stromal being mainly fibro muscular. Each can have varying amounts, providing a wide range of histological BPH presentations. The main activating component is DHT, that is converted within stromal cells from testosterone via enzyme 5alpha reductase, which is also produced by stromal cells (see fig 1). DHT has a function as an autocine/paracrine agent, causing direct cell stimulation, or up regulating mitogenic signals which act upon the proliferation of neighbouring cells. Testosterone as similar attributes to DHT, but it is nowhere near as potent. A reduction in the activity of DHT will cause the gland to shrink, however if the gland is very large, it may have to be dealt with surgically, e.g by use of trans urethral resection prostate (TURP). This can produce prostatic chippings, these must all be processed as there may be a background micro foci of cancer or PIN. 

Figure 1. Picture provided by Roy Stewarts "Prostate" lecture presentation.

DHT binds to nuclear androgen receptors in both epithelial and stromal prostate cells, DHT has a higher affinity for AR than T, forming a more stable complex. DHT binding promotes the transcription of androgen-dependent genes. DHT itself doesn't promote mitosis, however the DHT-mediated transcription of genes results in the production of many growth factors, such as FGF (fibroblast growth factor), with FGF-7 (keratinocyte growth factor) being important. Others produced are FGF 1 and 2, and TGF beta, that promotes the proliferation of fibroblasts. The overall cause of BPH isn't known, however DHT related growth factors ac by increasing stromal cell proliferation, and lead to a decrease in epithelial cells apoptosis.

The main feature of BPH is the presence of nodules. Their composition range from purely stromal and fibromuscular, to fibroepithelial with a glandular predominance. Glandular proliferation takes the form of aggregations of small to large cystically dilated glands, lined by 2 layers, inner columnar and an outer cuboidal or flattened epithelium.

BPH diagnosis cannot be made using a needle biopsy, as the histology of glandular or mixed glandular-stromal nodules cannot be appreciated in limited samples. They do not necessarily sample the transition zone where BPH occurs as this is in the middle of the prostate.    

5alpha reductase inhibition

Finasteride is used as an inhibitor for 5alpha reductase, it can inhibit its action by around 80-90%. As a result, the amount of DHT is reduced by 70% in serum, 90% in prostate and 34% in skin. The amount of testosterone increases by around 10%, and PSA is reduced by an average of 50%, as a result of this, the total prostate volume will decrease by 15-25%.  

BPH treatment

For cases which are moderate to severe that are resistant to medical therapy, there are a range of invasive procedures which can be used instead. TURP has been good in terms of reducing symptoms, improving flow rates and decreasing post-voiding residual urine. It is now used as the first line of therapy for those under certain circumstances, such as those with reoccurring urinary retention. However, as a result of its morbidity and cost, other procedures have been developed. Such as:

• High-intensity focused ultrasound
• Laser therapy
• Hyperthermia
• Transurethral electrovaporisation
• Transurethral needle ablation using radiofrequency
• Prostate artery embolisation as recently been trailed as a therapy also

Nodular hyperplasia is not considered to be a premalignant lesion. 

Prostate cancer

Prostate cancer is the most common cancer within men. Statistics show approximately every hour one man dies from prostate cancer, meaning over 10,000 every year. Over 40,000 men are diagnosed with prostate cancer every year, more than 100 a day. Estimated that in 2030, prostate will be the most common cancer type. 1 in 8 men will get this. There are many risk factors which aid in the formation of prostate cancer:

• Age
• Family history: this is one of the strongest risk factors, 5-10% of PC cases and 30-40% of early onset cases (those who develop it before the age of 55) are caused by inherited susceptibility genes. There is a 2-3x increase in risk for those who have a first degree relative diagnosed with PC, if the relative was under the age of 60, or the person has more than one relative with PC, the risk exceeds the average by 4x. If the person has more than one relative when an early onset of PC, the risk increases 7x. If there is a history of breast cancer, especially under the age of 60, this will also increase the risk, due to an association with BRCA1 and 2. Studies have identified a number of risk-associated loci, including one at 8q24 which appears to selectively increase the risk among African men. 
• Ethnicity: the incidences of which PC occur differ in varying locations in the world, suggesting ethnicity is a factor. In the UK, black caribbean and african men have 2-3 x the risk of developing PC than white men, and asian men have an even lower risk, this trend is also seen in the US.
• Life style: migration studies have shown that men moving from low risk to high risk areas have showed an increase in cases, suggesting that life style factors of the area also play a role, e.g a South Asian man living in the UK has a higher chance at developing PC than those living in South Asia. 
• Diet
• Alcohol and smoking
• Body weight and physical activity
• Medications, medical procedures and infections
• Endogenous hormones
• Diabetes mellitus

Cancer and gene arrangements

There is a common somatic mutation in prostate cancer which gives rise to chromosomal rearrangements (translocations) that juxtapose the coding sequence of an ETS family transcription factor gene (most commonly ERG and ETV1) next to the androgen-regulated TMPRSS2 promotor, testosterone increases. ETS over expression makes normal prostate epithelial cells more invasive, maybe by the up regulation of MMPs. Tumours with rearranged ETS genes do not necessarily have certain distinctive morphologic features, and a rarely have a differing gene expression signature than those who do not have different ETS arrangements, thus suggesting that ETS gene rearrangements define a specific molecular sub-class of prostate cancer. They may also have implications for prostate cancer during screening and early diagnosis, it's possible to detect ETS fusion genes in urine, through the use of PCR. Most aggressive fast growing PCs have these translocations. 

CAG repeat

Endogenous hormones, including androgens and oestrogens, have a likely influence of the carcinogenesis of the prostate. Men who have been castrated, such as eunuchs, whom have levels of testosterone equal to that of before puberty, will not develop prostate cancer. Thus, it is possible that a change in androgen biosynthesis and metabolism e.g the role of the androgen receptor (AR) CAG repeat in exon 1, could influence the risk of PC. It has been reported that AR CAG repeat length greater than, or equal to 20 repeats, conferred a protective effect for PC in men. Long repeats make the cell less likely to divide.

Androgen resistant cancer

The term "castration-resistant prostate cancer" or CRPC arose from what used to be referred to as androgen-independant prostate cancer. The AR is considered the principle driver towards prostate cancer progression. This concept showed that castration temporarily slowed the progression of PC, however subsequent castration-resistant growth of PC has been attributed to a variety of mechanisms, including: 

• activation by receptor tyrosine kinases from growth factors, 
• loss of cell cycle regulators and someones 
• genomic mutations in the AR allowing response to nonspecific AR ligands. 
• It has been showed that increased AR expression was the most common event associated with CRPC growth. 
• It has also been shown that metabolic adaptation is involved also, involving the production of androgen within the tumour cells, self stimulatory. 
• Many studies have revealed there are many alternative splice forms of AR, these variants have differing structures, however each variant lacks portions of the ligand-binding domain (LBD), a feature predicted to produce a constitutively active receptor. 
• The variants increased expansion was associated with a more rapid disease occurrence, following radical prostatectomy for localised disease. 

Aggressive cancer "Pussycat vs Tiger"

5 single nucleotide polymorphisms (variations within a gene) were located in, or associated with 5 genes which may affect PC progression:

1. LEPR: This is the strongest marker with PC mortality, it aids in tissue growth control, inflammation, development of blood vessels and the density of bones. These make this gene an interesting candidate for understanding disease progression, as the primary metastatic site for PC is bone, and these metastases are predictive of fatal disease.
2. RNASEL: This gene is associated with hereditary PC, and associated with apoptosis, inflammation and the proliferation and adherence of cells (cancer growth hallmarks).
3. IL4: Interleukin 4, associated with growth of tumours, blood vessel development and cancer cell migration.
4. CRY1: Cytochrome 1, gene that impacts the circadian rhythm this possibly affecting androgen levels. 
5. ARVCF: member of the catenin protein family, aids in the communication of inside and outside cells. Increased expression has been shown to disrupt adhesion of cells, possibly facilitating cancer progression.

Patients whom carried 4 or 5 of these markers had a 50% increased risk of dying of PC than  those with 2 or less. There is a correlation with death rate and the number of SNPs present.

BRCA2

BRCA2 is now not only associated with early development of PC, but also with the aggressive form. It is found in 1:100 of PCs. If there is a family history of breast or prostate cancer, then this gene should be tested for, however this isn't currently available within the UK. 

Prostate specific antigen (PSA)

PSA is often used as a tool for screening PC, however elevated levels can also be present in benign tumours, and some malignancies may have low levels, however the cut off is given at 4.0 ng/ml. A better way to measure this gene is via its velocity, or rate of change over time, the value 0.75 ng/mL per year best distinguishes between men with and without PC. In order to be considered efficient, there must be a minimum of 3 tests over a period of 1.5-2 years. Best used as a marker of treatment.

PSA vs volume: including the ratio of serum PSA value and volume of prostate gland (PSA density). Men with enlarged hyperplastic prostate glands have a higher overall serum PSA than men with smaller glands. Measuring serum PSA density factors out benign prostatic tissue contribution to serum PSA levels. This is calculated by diving the total serum PSA level by the estimated gland volume (determined by transrectal ultrasound measurements) in order to estimate the PSA produced per gram of prostate tissue. 

As men age, their prostates tend to become enlarged with BPH. Overall older men would have a higher serum PSA level than younger men. Thus there are reference ranges for upper age-specific PSA:

• 2.5 ng/ML - 40-49 years of age
• 3.5 ng/mL - 50-59 years of age
• 4.5 ng/mL - 60-69 years of age
• 6.5 ng/mL - 70-79 years of age

Free PSA: Immunoreactive PSA (the form which is detected by antibody tests) exists in 2 forms, a major fraction bound to alpha1-antichymotrypsin, and a minor free fraction. The % of free PSA (free PSA/total PSA x 100) is lower in men with PC than those with BPH. Free PCA higher than 25% indicates a lower risk of cancer, as compared to free PSA values of less than 10%, which can cause concern for cancer. 

Biopsies
Talk about this more (will be updated soon). Braccotherapy (implant therapy) - insert a core of radioactive material.

Histological diagnosis of PC

Most lesions are adenocarcinomas which produce well-defined, readily demonstrable gland patterns. These glands are typically smaller than benign glands, and are lined by a single uniform layer of cuboidal or low columnar epithelium. In contrast to benign glands, which have two layers, the outer basal cell layer found in benign glands is absent in adenocarcinomas. These inner cells cannot be stained, whereas the outer basal cells can. PC glands are crowded, and lack branching and papillary infolding. The cytoplasm of the tumour cells range from pale-clear, as noted in benign glands, to a distinctive amphophilic appearance. The nuclei in PC are large, and sometimes a cell can contain more than one. There is also variation is nuclear size and shape, however blatant pleomorphic features are not present. Mitotic figures are uncommon. 

Diagnosis

Difficulty in establishing an appropriate diagnosis with PC stem, not only due to the small amount of tissue available for examination from the needle biopsy, but also that a biopsy often only samples a new malignant glands among many benign glands. Morphologically, PC malignancy clues are very subtle, again making it hard to efficiently diagnose. There are many benign mimickers of cancer which can lead a pathologist to a misdiagnosis. There are very few histologic findings on a biopsy which are specific PC, however a perineural invasion is one. The general diagnosis is made based on a combination of morphological and ancillary findings. 

Diagnostic aids: A distinguishing feature between benign glands and malignant glands is the presence of basal cells, these are only present in benign glands. This can be exploited by the immunohistological use of markers which are specific to basal cells, such as high molecular weight cytokeratins 34bE12, 1, 5, 10, 14 and also P63. Another marker which is very selective for PC cells and not normal cells is AMACR (alpha-methylacyl-coenzyme A-racemase), this is up regulated in PC and can be observed by the use of immunohistochemistry. The majority of PCs are positive for AMACR, with sensitivities varying from 82%-100%. AMACR is a positive stain for malignancy, must be used with H&E.

AMACR

P504S is a 382 aa cytoplasmic protein which has been recently identified by microarray screening of prostatic carcinomas, it has been identified with AMACR, which is an enzyme that catalyses the racemization of alpha-methylacyl branches carbolic coenzyme A thioesters. It is located within the mitochondria and peroxisomes, where it aids in the oxidation of branched chain fatty acids. It is also responsible for the racemization of an intermediate in the synthesise of bile acids. In neoplasia, AMACR is most often expressed in tumours associated with a high fat diet, such as colonic and prostatic carcinoma. AMACR stains red, and CK and P63 stain brown. 

Prostatic intraepithelial neoplasia (PIN)

In around 80% of cases, prostatic tissue removed from a carcinoma will also contain presuming precursor lesions, referred to as PIN. These consist of architecturally benign prostatic acini (sac like cavity) lined by cytologically atypical cells with prominent nucleoli. PIN and carcinomas may be identical cytologically, however architecturally PIN involves larger branching glands with papillary infolding, compared to invasive cancer that is typically characterised by small crowded glands with straight luminal borders. PIN glands are surrounded by a layer of basal cells, alongside an intact basement membrane - there are many types of evidence relating PIN to invasive cancer. For example, both typically predominate in the peripheral zone, and are uncommon on other zones. 

Comparing a non cancerous prostate to one with cancer, those with have a higher frequency, and a greater extent of PIN. PIN is often observed near cancer, sometimes with cancer budding off from it. A high number of molecular changes observed in invasive cancers can also be witnessed in PIN, providing evidence that PIN is a type of intermediate between normal and invasive cancer. But how PIN behaves and develops into cancer is not known. thus as used in cervical cancer, the term "carcinoma in situ" cannot be applied to PIN. However, PIN is important in identifying BPH chippings. 

Benign glands have a continuous basal layer, PIN glands have a fragmented basal layer, and malignant glands have no basal layer. 

Grading

The Gleason system is used to grade prostate cancer. PCs are stratified into 5 grades, on the basis of their glandular patterns of differentiation. It's a subjective assessment. 

• Grade 1: represents the most well-differentiated tumours, in which the neoplastic glands are uniform and round in appearance and are packed into well-circumscribed nodules.
• Grade 5: tumours show no glandular differentiation, and the tumour cells infiltrate the stroma in the form of cords, sheets and nests. 

All other grades fall in between these. 

Most tumours contain more than one pattern, so a grade is given to the most dominant pattern, and another grade to the most frequent pattern, the two grades are then added together to give a combined Gleason score, thus the number can be between 2 and 10. The scores are combined into groups with similar biological behaviour;

• 2-4: represent well differentiated cancer, typically found in small tumours within the transition zone. In surgical specimens, low-grade cancer is typically an incidental finding on TURP, which is performed for symptoms of BPH.This is why all chippings are sampled. 
• 5-6: intermediate grade tumour: the majority of potentially treatable cancers detected on a needly biopsy as a result of screening have a score of  5-7. 
• 7: moderate to poorly differentiated tumour
• 8-10: high-grade tumour, these tend to be advanced cancers that are unlikely to be cured. 

Although PCs can become more aggressive with time, the score usually remains stable over several years. Grading is very important in PC as the grade and stage are the best prognostic predictors. 

The state of DNA ploidy can affect the Gleason score, with the score usually being higher when DNA ploidy is abnormal.

Staging and risk

Low risk; clinical stage T1c, or T2a, PSA level less than 10 ng/ML, GS of 2-6.

• Very likely the disease is within the prostate (confined)
• Minimal risk of spread to distant sites such as bones
• Prostate-only treatment (implant alone) is appropriate
• Observation is an appropriate option in selected individuals
• Extremely high cure rate with all therapies

Intermediate risk; clinical stage T2b, PSA 10-20 ng/mL, GS of 7.

• Possible disease is beyond the prostate (not necessarily confined)
• Low but significant risk of metastasis
• Implant alone is appropriate for some patients, however combination therapy is an excellent option
• Observation is rarely appropriate
• High cure rate with implant based therapies

High risk; clinical stage T2c, PSA over 20 mg/mL, GS of 8-10

• Very likely disease has progressed beyond the prostate
• Probable risk of metastasis
• Combination therapy is needed
• Observation is never appropriate
• Curable with intensive treatments - body wide treatments such as hormone therapy are often combined with radiation treatments.

Recent studies have indicated the presence of the gammaretrovirus XMRV being present in a significant amount of PCs, this may be of relevance?