Karsinoma Prostat

01Pathophysiology

Prostate carcinoma is overwhelmingly an adenocarcinoma (>95% of cases), arising from the glandular epithelium of the prostate. The key anatomical concept is that it arises from the peripheral zone of the prostate, which is the region most accessible to the examining finger during a digital rectal exam. This is in contrast to benign prostatic hyperplasia (BPH), which arises from the transitional (periurethral) zone. Understanding this distinction explains why early prostate cancer does not cause obstructive urinary symptoms the way BPH does: the peripheral zone is far from the urethra.

The development of prostate carcinoma is androgen-dependent. Testosterone is converted to dihydrotestosterone (DHT) by the enzyme 5-alpha reductase within prostatic cells. DHT binds to intracellular androgen receptors, driving cellular proliferation. This hormonal dependency is the entire foundation of treatment for advanced disease: removing the androgen signal causes tumor regression. Over time, however, tumor cells can acquire androgen independence (castration-resistant prostate cancer), which carries a much worse prognosis.

Prostate cancer has a characteristic pattern of metastasis. It spreads locally through the prostatic capsule into the seminal vesicles and bladder base. Distant spread occurs predominantly to bone via the Batson vertebral venous plexus, a valveless venous network that directly connects the prostatic venous drainage to the vertebral column. This explains the classic finding of osteoblastic (sclerotic) bone metastases, particularly in the lumbar spine and pelvis. Osteoblastic lesions are critical to recognize because most other carcinomas that metastasize to bone produce osteolytic (destructive) lesions. The osteoblastic pattern is a high-yield discriminator for prostate origin.

Elevated alkaline phosphatase in a man with known prostate cancer strongly suggests bony metastatic disease, because osteoblastic activity drives alkaline phosphatase production. Additionally, PSA (prostate-specific antigen) is produced by both normal and malignant prostatic epithelium. PSA is organ-specific but not cancer-specific: it can be elevated in BPH, prostatitis, urinary retention, and after prostatic manipulation.

02Classification and Clinical Manifestation

Gleason Grading System

The Gleason score is the standard histological grading system for prostate adenocarcinoma. A pathologist assigns a grade (1 through 5) to the two most prevalent architectural patterns seen on biopsy. The two grades are summed to produce the Gleason score (range 2 to 10). The dominant pattern is listed first.

A testable nuance: a Gleason 3+4=7 and a Gleason 4+3=7 are not equivalent. The 4+3 pattern carries a worse prognosis because the dominant (first listed) pattern is higher grade.

TNM Staging and Clinical Presentation

03Diagnostic Workup

Best Initial Test: The combination of DRE and serum PSA serves as the entry point. In a clinical vignette, a man over 50 presenting with an abnormal DRE finding (hard nodule) or an elevated PSA should prompt further evaluation. Remember that PSA alone is neither sensitive nor perfectly predictive: PSA can be elevated in BPH, prostatitis, and after instrumentation or ejaculation.

Next Step After Abnormal Screening: When PSA is elevated or DRE is abnormal, the next step is a TRUS-guided prostate biopsy. This is the gold standard for diagnosis. Newer protocols incorporate multiparametric MRI before biopsy (MRI-TRUS fusion biopsy) to improve sampling accuracy, but the core concept for testing purposes remains: tissue diagnosis is required to confirm cancer and assign a Gleason score.

Free-to-Total PSA Ratio: In cases where PSA is in the "gray zone" (4 to 10 ng/mL), the free-to-total PSA ratio helps differentiate cancer from BPH. A low free-to-total PSA ratio (<10 to 15%) suggests cancer, because malignant cells produce more protein-bound (complexed) PSA. A high ratio suggests BPH.

Metastatic Workup: For patients with a Gleason score $\ge 8\backslash geq\; 8$, PSA >20 ng/mL, or T3/T4 disease, a radionuclide bone scan is indicated to detect skeletal metastases. The classic finding is multifocal osteoblastic (sclerotic) uptake in the axial skeleton.

04Management and Treatment

Active Surveillance is a critical concept for testing. It applies only to very low-risk, low-volume disease. The rationale is that many low-grade prostate cancers are clinically indolent and will never cause morbidity or mortality during the patient's lifetime. Overtreatment exposes these patients to unnecessary risks of incontinence and erectile dysfunction. Surveillance does not mean "doing nothing"; it involves structured monitoring with PSA, DRE, and repeat biopsies.

Androgen Deprivation Therapy (ADT) is the cornerstone of treatment for advanced and metastatic disease. The two main approaches are:

1. Medical castration: GnRH agonists such as leuprolide. These initially cause a transient testosterone flare (surge) before receptor downregulation suppresses testosterone production. To prevent the clinical consequences of flare (worsening bone pain, spinal cord compression), an antiandrogen (e.g., flutamide, bicalutamide) is given for the first few weeks.

2. Surgical castration: Bilateral orchiectomy. Equally effective, immediate, and irreversible.

A high-yield testing point: GnRH antagonists (e.g., degarelix) suppress testosterone without causing a flare, making them preferable in patients at risk for acute complications from flare (e.g., impending spinal cord compression).

Side Effects of ADT are commonly tested: hot flashes, sexual dysfunction, gynecomastia, osteoporosis, metabolic syndrome, increased cardiovascular risk, and anemia.

Radical Prostatectomy is the primary surgical option for localized disease. Complications include urinary incontinence and erectile dysfunction. Post-prostatectomy, PSA should drop to undetectable levels. Any detectable PSA after surgery indicates residual or recurrent disease (biochemical recurrence).

Radiation Therapy (external beam or brachytherapy) is an alternative curative modality for localized disease. Side effects include radiation proctitis and cystitis.

05Differential Diagnosis and Distractors

06Traps and High-Yield Pearls

The most common way students miss questions on prostate carcinoma is by confusing it with BPH based on urinary symptoms alone. Vignettes testing prostate cancer typically describe an asymptomatic older man with an abnormal DRE finding or an incidentally elevated PSA, not someone with classic lower urinary tract symptoms. When obstructive symptoms are present in a cancer vignette, it usually indicates locally advanced disease. The hard, irregular nodule on DRE is the single most reliable clue that separates malignancy from BPH.

Another frequent trap involves the testosterone flare with GnRH agonists. A vignette may describe a man started on leuprolide who develops acute worsening of bone pain or signs of spinal cord compression days after starting therapy. The correct explanation is the initial testosterone surge, and the correct preventive measure is co-administration of an antiandrogen at the start of therapy, or using a GnRH antagonist instead.

Students also commonly forget that PSA is organ-specific but not cancer-specific. A moderately elevated PSA in the setting of acute urinary retention, recent catheterization, or prostatitis should not be reflexively attributed to malignancy. The free-to-total PSA ratio and clinical context guide the decision to biopsy.

Finally, when a vignette describes osteoblastic bone lesions on imaging in an older man, prostate carcinoma should be the leading diagnosis until proven otherwise. This is the prototypical bone-forming metastatic pattern, and recognizing it is a core competency being tested.