Prostate, General Concepts



Prostate, General Concepts


Gladell P. Paner, MD








Anterior image, posterior image, postero-lateral image views show an inverted conical gland with broad base and tapered apex. Seminal vesicles image and flat posterior surface image are orientation landmarks.






McNeal anatomic model of prostate depicts the internal structural relationship of peripheral (green), central (orange), and transition (blue) zones, and the anterior fibromuscular stroma (yellow).


ANATOMIC FEATURES


Prostate Gland



  • Exocrine compound tubulo-alveolar gland


  • Located in true pelvis



    • Surrounded by urinary bladder superiorly, transverse urogenital diaphragm inferiorly, inferior aspect of symphysis pubis anteriorly, and rectum posteriorly


  • Inverted conical shape: Base is broad superior region, and apex is tapered inferior region



    • Base contiguous with bladder neck superiorly and seminal vesicle attachment posteriorly


    • Apex blends with striated muscle of transverse urogenital diaphragm


  • Normal prostate in men (21-30 years old) weighs ˜ 20 g (range 14-26 g)


  • In adults, usually measures 4 x 3 x 2 cm



    • Widest at transverse dimension of base


  • McNeal anatomic model divides prostate into glandular and nonglandular components



    • Glandular component



      • Peripheral zone, central zone, transition zone, periurethral gland region


    • Nonglandular component



      • Anterior fibromuscular stroma, preprostatic sphincter, striated sphincter


  • Receives arterial supply from inferior vesical and middle rectal arteries, branches of internal iliac artery


  • Prostatic venous plexus lies partly within prostatic fascial sheath and drains into internal iliac vein


  • Primary lymphatics drain into regional lymph nodes in true pelvis



    • Hypogastric, obturator, internal and external iliac, and sacral lymph nodes


Prostatic Urethra



  • Approximately 3 cm in length and begins at internal urethral orifice at apex of bladder trigone


  • Courses through prostate, makes anteriorly concave 35° bend, ends as urethra penetrates fascia of urogenital diaphragm and enters perineum


  • Continues distally as membranous urethra


  • Posterior wall of prostatic urethra has several unique features related to prostatic secretory function



    • Contains a longitudinal ridge (urethral crest) lined by 2 adjacent grooves (prostatic sinuses)


    • Prostatic ductules enter urethra predominantly in sinuses with fewer entering along lateral aspects of crest


    • Urethral crest also has midline protuberance (verumontanum or colliculus seminalis)


Verumontanum (Colliculus Seminalis)



  • Protrusion of prostatic tissue from posterior wall of urethra at angulation, tapers distally as crista urethralis


  • Contains epithelium-lined blind sac (utricle) between openings of paired ejaculatory ducts


Ejaculatory Duct



  • Passes through central zone entering at cephalad aspect


  • Both ducts open into prostatic urethra at verumontanum, lateral to prostatic utricle


Seminal Vesicle



  • Attached to superior-posterior aspect of prostate and bladder base


  • Paired, highly coiled epithelial-lined tubes with irregular outpouchings


  • Small intraprostatic portion is seen


  • Excretory duct connects anteriorly with ampullary portion of vas deferens forming ejaculatory duct


  • In adults, average 6 x 2 cm and contains up to 5 mL milky fluid, which forms bulk of ejaculatory volume



Periprostatic Structures



  • Resected prostate may include adjoining tissues, such as adipose tissue, neurovascular bundle, paraganglia, Denonvilliers fascia, and lateral prostatic fascia



    • Potency-sparing prostatectomy preserves neurovascular bundle, site of cavernous nerves important for erection


SPECIMEN TYPES AND HANDLING


Needle Core Biopsy



  • Indication is for histologic diagnosis of prostate cancer and evaluation of mass lesion or hypoechoic region


  • Performed for elevated serum PSA level &/or abnormal digital rectal examination (DRE)


  • Performed almost universally via transrectal ultrasound (TRUS)-guided using 18-gauge needle as outpatient procedure


  • May also be performed perineally or transurethrally


  • Different prostate biopsy sampling schemes



    • Sextant biopsy (6 cores)



      • Use remains widespread despite becoming the less preferred technique


      • Samples bilateral base, midgland, and apex


    • Extended biopsy (10-12 cores)



      • Preferred initial diagnostic procedure


      • Demonstrated increased cancer detection rate without increase in morbidity


      • False-negativity rate of 5% (vs. ~ 25% for sextant biopsy)


      • Optimal extended biopsy includes standard sextant area plus cores that target mid and lateral peripheral zone


      • Transition zone biopsy is not usually recommended at initial biopsy due to low detection rate


    • Saturation biopsy (≥ 20 cores)



      • Does not improve cancer detection when performed as initial procedure


      • Considered in men with persistently elevated PSA and several prior negative biopsies


      • Includes biopsy of transition zone


  • Handling of biopsy specimen



    • If possible, avoid accessioning prostate biopsy specimens in sequence


    • Count and document number of cores per container



      • Ideally core(s) submitted in 1 container per site (> 3 is detrimental for evaluation)


    • Formalin fixative is preferred



      • Bouin solution is not preferred as it may enhance nucleoli in benign glands


    • Hematoxylin or other indelible dye makes tissue cores more visible when cutting paraffin blocks


    • Ideally, submit only 1-2 tissue cores per block to maximize tissue representation



      • More cores per block often leads to undesired tissue loss


    • Prospectively cut intervening unstained slides to ensure presence of atypical focus for adjunctive immunostains



      • Levels 1, 3, and 5 for H&E staining


      • Save unstained levels 2, 4, and 6 for potential immunohistochemistry (IHC) or H&E stains


      • Attempting immunostains on subsequent deeper levels more frequently results in loss of atypical focus


    • Multiple sections (ideally 3) should be present on each H&E slide to enhance sampling


    • Most of the tissue in the block from superficial to deep should be included in sections


Fine Needle Aspiration Biopsy



  • Rarely performed in USA



    • Advocates claim aspiration cytology is cheaper, faster, easier to use, and has less morbidity


    • Major drawback is lack of cancer architecture that precludes Gleason grading and distinction from HGPIN



      • Inability to provide important information for planning therapy and prognostication


Transurethral Resection of Prostate (TURP) or Subtotal Prostatectomy



  • TURP is surgical treatment of choice for benign prostatic hyperplasia (BPH)


  • Open simple prostatectomy may be performed for bulky BPH


  • Incidental prostate cancer encountered in ~ 10%


  • TURP specimen consists of elongated rubbery fragments called prostate chips



    • Includes transition zone and areas around proximal prostatic urethra


  • Handling of TURP specimen



    • Specimens ≤ 12 g: Submit entirely


    • For > 12 g: Submit initial 12 g (6-8 cassettes) and 1 cassette for every additional 5 g


    • Sensitivity for cancer detection may be increased by selectively submitting chips that are firm, yellow, or grossly suspicious for cancer


    • If incidental prostate cancer comprises < 5% of tissues examined, entire remaining tissue should be submitted


Radical Prostatectomy (RP)

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Jul 7, 2016 | Posted by in PATHOLOGY & LABORATORY MEDICINE | Comments Off on Prostate, General Concepts

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