Pathology Of Prostate

The prostate in a normal male weighs about 20g and encircles the neck of the bladder and the urethra. In the embryo, the gland is divided into 5 lobes—anterior, posterior, middle and two lateral. In the adult, there are 4 functionally and anatomically distinct zones: peripheral, central, transitional and periurethral. Most cancers arise in the peripheral zone, which makes it easier to detect them with DRE, while most hyperplasia occurs in the transitional and periurethral zones, where they can obstruct the outflow of urine.

1)Infamation

2)Hyperplasia

3)Tumors

1. Inflammation

This can be acute bacterial, chronic bacterial or chronic abacterial. Most cases of acute bacterial prostatitis are caused by various strains of E.coli and present with fever, chills and dysuria.

Chronic bacterial prostatitis is caused by the same bacteria as the acute form, but it presents without an antecedent acute episode with low back pain or suprapubic discomfort, or it can be asymptomatic.

Chronic abacterial prostatitis shows no growth on culture of urine or prostatic secretions and is caused most likely by Chlamydia or Ureoplasma.

2. Hyperplasia

Bening prostatic hyperplasia (BPH) refers to nodular enlargement of the periurethral region of the prostate that occurs with aging in almost all men. This process is mediated by DHT and estrogens which signal the transcription of growth factors in the prostatic cells—treatments with 5-reductase inhibitors tend to decrease the size of the prostate.

Usually, the prostate enlarges to a weight of about 100 grams, although it can grow much larger.

Although about 50% of men with BPH are asymptomatic, those in whom urethral obstruction is present complain of increased frequency, nocturia, difficulty in starting and stopping the urine stream, overflow dribbling and dysuria. The bladder responds to increased pressure by developing trabeculae, diverticula and hypertrophy. In some cases, urinary retention leads to hydronephrosis and UTI’s secondary to stasis of urine. BPH is not a premalignant lesion and does not increase the risk of cancer.

3. Cancer

Prostate carcinoma is the second common form of cancer in males (perhaps after lung cancer or skin cancer) and the second leading cause of cancer death. This is a disease of older men, with almost all cases reported in men over 50.

Clinically, prostate cancer arises mostly in the peripheral zone and presents as a hard, immovable prostatic nodule on DRE, which makes annual rectal exam in men >50 a very important screening tool. Histologically, the tumor looks like crowded, “back-to-back” glands lined by single layer of cuboidal epithelium. It is also important to note if the tumor has invaded the capsule, broke through it or is contained entirely in the gland.

The tumors are graded based on the Gleason system. This system grades the tumor 1-5 based on degree of differentiation, 1 being the most well-differentiated, 5 being the least. Because most tumors demonstrate more than one pattern, the dominant pattern and the secondary pattern are assigned their own scores and added. If there is only one pattern, the score is doubled. This system correlates well with prognosis. The tumors are staged according to degree of invasion and extensiveness of metastases.

Prostate cancer most commonly metastasizes to bone, primarily lumbar vertebrae, where it can produce osteolytic as well as osteoblastic lesions (Robbins, 6^th ed.) and causes severe back pain or pathologic fracture of the vertebrae. Prostate CA is the only tumor that does not just lyse the bone but actually builds it up.

Diagnosis

The diagnosis of prostate cancer is based on clinical observations and has to be confirmed with a transrectal biopsy of the gland. PSA (prostate specific antigen) can be used to guide clinical investigation and to monitor for relapse of the disease after treatment but is not a good screening tool because it is not cancer-specific—BPH can also produce increases in serum PSA levels. Furthermore, some patients with prostate-confined cancer can have normal PSA values. Generally, PSA values less than 4 ng/ml are considered normal and those >10ng/ml indicate the need for further workup, with values in between being borderline. With borderline values, the percentage of free (unbound) PSA can be used—free PSA is lower in patients with cancer than in men with BPH (remember, it’s good to be free, so you want increased free PSA)

The treatment protocols for prostate cancer are still debated and not firmly established. Generally, treatments consist of surgery, radiotherapy, hormonal manipulation or just watchful waiting.

Category: Pathology Notes