Approximately 95% of all prostate cancers are adenocarcinomas. Roughly 4% of all prostate malignancies arise from the transitional epithelium of the urethra or ducts as transitional cell carcinoma. Primary carcinoid tumours of the prostate, sarcomas, and primary small cell carcinomas of the prostate are rare, Tumours of other organs may spread into the prostate. Premalignant changes in the epithelium are referred to as prostatic intraepithelial neoplasia (PIN).
PIN is divided into low and high grade and includes the continuum from uncontrolled hyperplasia to the development of an anaplastic morphology with nuclear polymorphism and microinvasion of the basement membrane. PIN has been seen in over 70% of prostates with invasive prostate cancer. (11 12) It is seen much less frequently in normal prostates removed at necropsy. Around 40% of non-cancerous prostates harbour PIN.
At present, the prognostic value of prostatic biopsy specimens containing PIN is indeterminable, in other words we do not clearly know whether PIN progresses to invasive cancer in a fashion that parallels tumour development in other organs such as cervix. Histological recognition of prostate cancer depends on the overall assessment of the architecture and upon the cytology of individual cells. The prostate cancer cell cytoplasm may contain large amounts of acid phosphatase and prostate specific antigen (PSA).
Using immunohistochemistry for these antigens it is possible to differentiate prostatic carcinoma cells from other tumour cells. Grading is based on glandular differentiation and the system most commonly employed is the Gleason method. The grades are as follows: Grade 1: Well differentiated carcinoma with uniform gland pattern. Grade 2: Well differentiated with glands varying in size and shape. Grade 3: Moderately differentiated carcinoma with either (a) irregular acinae often widely separated or (b) well defined papillary/ cribriform structures.
This is the commonest pattern seen in prostate cancer. Grade 4: Poorly differentiated carcinoma with fused glands widely infiltrating the prostatic stroma. Grade 5: Very poorly differentiated carcinoma with no or minimal gland formation. Tumour cell masses may have central necrosis. The Gleason combined grading allows the two most predominant forms of glandular differentiation to be scored separately. The Gleason score correlates well with the prognosis in localised prostate cancer. There is considerable inter and intra observer variation in the reporting of tumour grade.
Symptoms of prostate cancer may include passing urine often with difficulty in the form of interrupted or weak flow, total inability to urinate or pain or burning during urination. Blood may also be present in urine or semen and males may have problems ejaculating. There is also sometimes a nagging back, hip or pelvic pain. However these symptoms are not unique to prostate cancer and are often representative of other clinical conditions. Usually prostate cancer does not demonstrate any visible sign of its presence. Screening is therefore extremely important if the disease is to be detected and treated early.
Having annual physical exams along with prostate specific antigen (PSA) blood test and a digital rectal exam (DRE) (shown in Figure D). A digital rectal exam should be done annual among men over 50 but those at higher risks should consider beginning exams earlier. PSA along with PAP (prostatic acid phosphatase) tests should also be done yearly. Fewer than 10% of patients with prostate cancer are diagnosed at screening assessments in the UK, and the vast majority are diagnosed because of their presentation with symptoms.
The diagnosis must be confirmed by histological examination of the prostatic tissue. Transrectal biopsy is widely favoured. Fine needle aspiration cytology as a means for diagnosis has not gained widespread popularity probably due to its limited sensitivity when compared with needle biopsy. PSA is an effective tumour marker in prostate cancer, but its use as a screening tool in the early detection of prostate cancer is controversial. Computed tomography of the pelvis is currently the most commonly employed imaging modality for assessing the extent of local spread of prostate cancer.
Despite initial enthusiasm, the use of transrectal ultrasound has not proven to be more useful at determining seminal vesicle involvement or extracapsular spread than digital rectal examination. Magnetic resonance imaging (MRI) appears to have equal sensitivity to computed tomography for detection of pelvic lymph node involvement. Bone scans are used routinely and have a false negative rate of 11%. MRI is the most sensitive technique for detecting bone metastases in prostate cancer but it is limited by its relative inability to image the whole skeleton.
Once abnormalities are detected in the DRE or PSA then a transrectal ultrasound may be recommended. This exam uses sound wave echoes to produce an image of the prostate glands. This image is then visually inspected by the physician for abnormalities. A CT or CAT scan (computed tomography scan) is an imaging procedure which uses a combination of x-rays and computer technology to render a cross-sectional image of the prostate. MRIs, are also used for imaging. A radionuclide bone scan may be used to reveal if the disease has invaded the bones.
Lymph node and prostate biopsies take a sample of the suspected tissue which is then examined under a microscope to check for abnormalities. Diagnosis of cancer is confirmed only by a biopsy. The most frequently used staging classifications are the revised 1997 TNM classification of the International Union Against Cancer (UICC) and the Whitemore-Jewett system. The TNM classification has the advantage in separating the assessment of the primary tumour from that of nodal disease and metastatic state.
The pathological classification of the TNM system corresponds to the clinical classification and is indicated by the prefix “p”. Shroeder et al found that 52. 3% of 262 tumours classified as T1 and T2 were upgraded to pT3, and 15. 1% of 152 T3 tumours were downstaged to pT2 after radical prostatectomy. The very early stages of prostate cancer usually go without symptoms and is increasingly diagnosed at routine rectal examinations. The typical finding is a firm, hard, or craggy, enlarged gland.
There may be obliteration of the median sulcus or spread to the lateral pelvic walls As the tumour arises usually in the peripheral zone of the prostate, symptoms of prostatism are late events or may result from accompanying benign prostate hyperplasia. Haematuria is uncommon but may occur secondary to infection or erosion of the gland. Perineal pain may occur in advanced disease. Weight loss, cachexia, bone pain, and neurological complications are seen later and are related to metastases.