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Prostate Gland

  1. Normal Structure And Function
    1. The prostate gland surrounds the bladder neck and proximal urethra.
    2. It consists of five lobes, separated by the urethra and ejaculatory ducts.
    3. Two lateral lobes and an anterior lobe enclose the urethra.
    4. The two lateral lobes are marked by a posterior midline groove, palpable on rectal examination.
    5. The middle lobe lies between the urethra and ejaculatory ducts and the posterior lobe lies behind the ejaculatory ducts. Q
    6. The normal gland weighs about 20 g and is enclosed in a fibrous capsule.
    7. Within the prostate there are three main groups of glands arranged concentrically around the urethra: an inner peri-urethral group, submucosal glands and the external group or main prostatic glands.
    8. From all three groups, ducts converge and open into the prostatic urethra.
    9. Individual glandular acini have a convoluted outline, the epithelium varying from cuboidal to a pseudostratified columnar cell type depending upon the degree of activity of the prostate and androgenic stimulation. Q
    10. The epithelial cells produce acid phosphatase and the prostatic secretion that forms a large proportion of the seminal fluid for the transport of sperm.
    11. The normal gland acini often contain rounded concretions of inspissated secretions (corpora amylacea). Q
    12. The acini are surrounded by a stroma of fibrous tissue and smooth muscle. Q
    13. The blood supply to the prostate gland is from the internal iliac artery by the inferior vesical and middle rectal branches.
    14. The prostatic veins drain to the prostatic plexus around the gland and then to the internal iliac veins. 
  1. Prostatitis
    1. A variable inflammatory infiltrate is commonly seen in the prostatic stroma in glands enlarged by benign nodular hyperplasia.
    2. Its significance is sometimes uncertain; it may simply be associated with leakage of material from distended ducts into the stroma. Q
    3. A marked degree of stromal oedema and periductal inflammation may, however, contribute to urethral obstruction.
    4. Prostatitis implies a more prominent inflammatory lesion of the gland, often associated with a specific infective cause.
    5. Prostatitis may be: Q
      1. acute suppurative prostatitis-caused by coliforms, Staphylococcus, or Neisseria gonorrhoeae (gonococcus)
      2. chronic non-specific prostatitis
      3. granulomatous prostatitis-idiopathic, tuberculous, following transurethral resection, or allergic. 
  1. Acute suppurative prostatitis
  1. Acute prostatitis usually results from spread of infection along the prostatic ducts secondary to urethritis or cystitis.
  2. Common causative micro-organisms include coliforms, staphylococci and gonococci.
  3. Acute prostatitis may occasionally follow urethral catheterisation or endoscopy; more rarely, the infection is blood-borne. Q
  4. The lesion is characterised by difficulty in micturition with perineal or rectal pain. Q
  1. Chronic non-specific prostatitis
  1. Chronic non-specific prostatitis may develop from recurrent episodes of acute infective prostatitis.
  2. The prostate gland shows increased stromal fibrosis with an infiltrate of lymphocytes and plasma cells, associated with acinar atrophy. Q
  1. Granulomatous prostatitis
  1. Granulomatous prostatitis is a heterogeneous group of lesions, all of which may cause enlargement of the gland and urethral obstruction. Q
  2. The inflammatory component and associated fibrosis produce a firm, indurated gland on rectal examination which may mimic a neoplasm clinically; thus the importance of correctly diagnosing this uncommon group of conditions. 
  1. Idiopathic prostatitis
It may result from leakage of material from distended ducts in a gland enlarged by nodular hyperplasia.
There is a periductal inflammatory infiltrate which includes macrophages, multinucleated giant cells, lymphocytes and plasma cells, with associated fibrosis. 

Benign Nodular Hyperplasia
  • A common non-neoplastic lesion
  • Involves peri-urethral zone
  • Nodular hyperplasia of glands and stroma
  • Not premalignant
  1. Benign nodular hyperplasia is a non-neoplastic enlargement of the prostate gland which occurs commonly after the age of 50 years. Q
  2. About 75% of men aged 70-80 years are affected and develop variable symptoms of urinary tract obstruction.
  3. If severe and untreated, benign nodular hyperplasia may lead to recurrent urinary infections and, ultimately, impaired renal function
  4. Aetiology
  5. Benign nodular hyperplasia is thought to be related to a hormonal imbalance, although the exact mechanism is vuncertain.
  6. With increasing age, the androgen levels fall, with a relative rise in oestrogens.
  7. Oestrogens also increase the prostatic tissue sensitivity to androgens.

Clinical features
There are two main factors in the development of obstructive symptoms:
  1. The hyperplastic nodules compress and elongate the prostatic urethra, distorting its course. Q
  2. Involvement of the peri-urethral zone at the internal urethral meatus interferes with the sphincter mechanism. Q
As a result of these two factors, the severity of obstructive symptoms is not necessarily related to the size of the gland.
The resulting obstruction to the bladder outflow produces difficulty in micturition.
There is a delay in starting to pass urine with a poor or intermittent stream and dribbling at the end of micturition ('prostatism').
Haematuria may occur but is not common.
Digital examination of the gland per rectum reveals enlargement of the lateral lobes, often asymmetrical.
The gland has a firm, rubbery consistency, and the median groove is still palpable. 

  1. The hyperplastic process usually involves both lateral lobes of the gland.
  2. In addition, there may be a localised hyperplasia of peri-urethral glands posterior to the urethra and projecting into the bladder adjacent to the internal urethral meatus.
  3. This hyperplasia is described as 'median' lobe enlargement but does not correspond to the anatomical middle lobe.
  4. The cut surface of the enlarged prostate shows multiple circumscribed solid nodules and cysts).
  5. Histological examination reveals two components: hyperplasia both of glands and of stroma. The acini are larger than normal (some may be cystic) and are lined by columnar epithelium covering papillary infoldings). Q
  6. The acini may contain numerous corpora amylacea.
  7. Phosphates and oxalates may be deposited around these to form prostatic calculi.
  8. The stromal hyperplasia includes both smooth muscle and fibrous tissue.
  9. Some of the nodules are solid, being composed predominantly of stroma, and others also contain hyperplastic acini.
Prostatic Carcinoma
  1. Adenocarcinoma occurring usually >50 years
  2. Metastasises mainly to bone (osteosclerotic metastases)
  3. Obstructs bladder outflow
  4. Many are hormone (androgen)-dependent

  1. The aetiology of prostatic carcinoma is unknown, although it is probable that the hormonal changes which occur with increasing age are involved.
  2. With advancing age there is a decrease in circulating androgen levels.
  3. This decrease is associated with involution of the outer zone of the prostate, the area in which most tumours arise.
  4. A family history of the disease is relevant: there is a two- to threefold risk of the tumour developing in men with a first-degree relative in whom prostatic carcinoma was diagnosed under 50 years of age
  1. Carcinoma Q
    1. Arises in posterior subcapsular area of gland
    2. Adenocarcinoma
    3. Invasion of stroma and perineural spaces
    4. Asymmetric firm enlargement of prostate may be palpable per rectum
    5. Metastasises, especially to bone
  2. Clinical features
    The clinical presentation and features of prostatic carcinoma include:  Q
    1. urinary symptoms-difficulty or increased frequency of micturition, urinary retention
    2. rectal examination revealing hard craggy prostate
    3. bone metastases-presenting with pain, pathological fracture, anaemia
    4. lymph node metastases. 
      1. Most active tumours arise in the posterior lobe of the gland, in the subcapsular area. compares location of lesions in benign hyperplasia and prostatic carcinoma.
      2. A retropubic prostatectomy for benign hyperplasia does not remove the posterior zone; this explains why carcinoma may develop following such a 'prostatectomy'.
      3. The tumour appears as an ill-defined, grey or yellow, firm or gritty area. Q
      4. Histological grading systems have been devised for assessing the prognosis of prostatic carcinoma.
      5. The most widely used is that devised by Gleason, which grades tumours on a scale of 1-5. This is based on the degree of glandular differentiation and the architectural pattern of growth. Q
      6. A grade 1 tumour is composed of circumscribed areas of well-formed, uniform glands. Q
      7. A grade 5 tumour shows an infiltrative growth pattern of sheets of neoplastic cells with only poorly formed glands. Q
      8. Most tumours are heterogeneous and show a second growth pattern; the combined histological grades are then added to give a Gleason score, which correlates with prognosis.
Mode of spread
Spread of prostatic carcinoma may be:
  • direct-stromal invasion, prostatic capsule, urethra, bladder base, seminal vesicle
  • via lymphatics to sacral, iliac and para-aortic nodes
via blood to bone (pelvis, lumbo-sacral spine, femur), lungs and liver. 

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