Prostate gland & seminal vesicles

General

Anatomy & histology


Editorial Board Member: Bonnie Choy, M.D.
Deputy Editor-in-Chief: Maria Tretiakova, M.D., Ph.D.
Kenneth A. Iczkowski, M.D.

Topic Completed: 10 August 2021

Minor changes: 10 August 2021

Copyright: 2003-2021, PathologyOutlines.com, Inc.

PubMed Search: Histology[TI] prostate pathology "last 5 years"[DP]

Kenneth A. Iczkowski, M.D.
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Cite this page: Iczkowski KA. Anatomy & histology. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/prostatehistology.html. Accessed December 8th, 2021.
Definition / general
  • Knowledge of the normal prostate morphology can help with orientation and avoid confusion of these findings with cancer
Essential features
  • Benign hyperplasia expands the transition zone and obstructs the bladder outlet; cancer occurs mostly in the peripheral zone where it does not obstruct the bladder outlet
  • Secretory cells and basal cells are the main 2 layers of benign acini (glands) and the loss of basal cells is a key diagnostic feature of prostate cancer; other cell types in the epithelium include neuroendocrine cells and lymphoid cells
  • Prostate specific antigen is the most useful marker of secretory cells and 34 beta E12 / high molecular weight keratin is the most useful marker of basal cells
Anatomy
  • Apex contains some skeletal fibers from urogenital diaphragm
  • Seminal vesicles extend from posterior prostate to posterior surface of bladder
  • Ampulla of vas (ductus) deferens and terminal seminal vesicle duct form ejaculatory duct, join prostatic utricle to open into prostatic urethra
  • Denonvillier's fascia (also called rectovesical septum or rectoprostatic fascia): thin layer of connective tissue that separates prostate and seminal vesicles from rectum
  • Prostatic urethra begins on superior surface, descends almost vertically, with continuous prostatic utricle extending to posterior prostatic wall, exits anteriorly
    • Divided into halves by sharp 35° angle midway, at site of verumontanum (bulge along posterior proximal urethra, site of emptying of ejaculatory, central and transition zone ducts)
  • Peripheral zone ducts empty into distal urethra
  • Prostatic nervous plexus supplies prostate, seminal vesicles, corpus spongiosum, corpora cavernosum and urethra
Terminology
  • Regions (Eur Urol 1991;20:261):
    • Transition zone:
      • 5% of prostatic volume
      • 2 pear shaped lobes surrounding proximal urethra
      • Expands after age 50, causing nodular prostatic hyperplasia; may expand to 95% of gland (Urology 2017;105:136)
      • Site of 10% of prostate cancer
      • Contains moderately compact fascicles of smooth muscle
    • Central zone:
      • 25% of prostatic volume
      • Surrounds transition zone to angle of urethra to bladder base
      • Site of 5% of prostate cancer
      • Unlike peripheral and transition zones, ducts are large and irregular
      • Glands are complex with tall columnar, pseudostratified lining, papillary infoldings and epithelial bridging (can mimic high grade prostatic intraepithelial neoplasia or cribriform cancer)
      • Striking basal cell layer with eosinophilic cytoplasm
      • Stroma is densest in central zone, least dense in peripheral zone, in between for transition zone (Hum Pathol 2002;33:518)
    • Peripheral zone:
      • 70% of prostatic volume, from apex posterior to base, surrounds transition and central zones
      • Site of > 80% of prostate cancer
      • Has loose fibromuscular stroma with widely spaced smooth muscle bundles, moderate gland complexity
Physiology
  • Function: conduit for urine, adds nutritional secretions to sperm to form semen during ejaculation; role in orgasm (Clin Anat 2018;31:81)
Diagrams / tables

Images hosted on other servers:
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Fundus

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Seminal vesicles and ducts

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McNeal zones

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Sagittal view

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Axial views

Clinical features
  • Embryologic model: 5 lobes, 2 lateral plus posterior, middle, anterior lobes
  • Other model (not used): 2 lateral lobes, small median lobe (contains posterior lobe, forms floor of urethra)
  • Current model (McNeal): transition, central, peripheral, periurethral zones (Prostate 1981;2:35)
    • Outer (cortical) zones are termed peripheral and central
    • Central is towards base
    • Inner (periurethral) zone is termed transition
Laboratory
  • Prostate specific antigen
Gross description
  • In young men: 20 g, funnel shaped, 4 x 3 x 2 cm
  • Within true pelvis, between bladder neck (base of prostate) proximally and urogenital diaphragm / levator ani muscle (apex of prostate) distally
  • Seminal vesicles are posterior and superior
  • Reference: Am J Clin Pathol 2001;115:39
Gross images

Contributed by Kenneth A. Iczkowski, M.D. and AFIP images
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Cross section of gland

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Normal gland

Microscopic (histologic) description
  • Secretory cells:
    • Located along glandular lumen
    • Columnar (except if atrophic)
    • Nucleoplasm is dark purple
  • Basal cells:
    • Separate secretory cells from basement membrane
    • Consist of low cuboidal epithelium and columnar mucus secreting cells
    • Nucleoplasm is lighter blue and may have prominent nuclear grooves, vacuoles
    • Are reserve cells (stem cells) and can undergo myoepithelial metaplasia but are not myoepithelial cells
    • Undergo hyperplasia causing multilayering and possibly prominent nucleoli in reactive / inflamed prostates
    • Their presence distinguishes benign conditions (basal cells present) from well differentiated adenocarcinoma (basal cells absent), although prostatic intraepithelial neoplasia and intraductal carcinoma retain at least focal basal cells; also, invasive cancer can retain rare basal cells (Am J Surg Pathol 1999;23:147)
  • Neuroendocrine cells:
    • Sparse and irregularly distributed population, function is not understood; not perceptible without stains (Precis Clin Med 2021;4:25)
  • Immune cells:
    • Modest component of lymphocytes is normal in prostates of all ages, mainly T cells, which are more numerous in the stroma than the epithelium; neutrophils are abnormal and may correlate with clinical prostatitis and raised serum PSA (Prostate 2003;55:187)
Microscopic (histologic) images

Contributed by Kenneth A. Iczkowski, M.D.
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Whole mount histology

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Close up, anterior aspect

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Basal versus secretory cells

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Basal cell hyperplasia

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Differential diagnosis of a multilayered epithelium

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Hyperplastic central zone

Virtual slides

Images hosted on other servers:
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Benign prostatic glands, stroma

Board review style question #1
Which of these immunostains marks luminal cells but not basal cells in normal prostate?

  1. Androgen receptors
  2. CK5/6
  3. Cytokeratin 903 (34 beta E12 / high molecular weight keratin)
  4. p63
  5. PSA
Board review style answer #1
E. PSA will be positive in luminal cells but is not part of the basal phenotype; proliferations and tumors derived from basal cells are also PSA negative. Customary markers used for basal cells include nuclear p63 and cytoplasmic basal cell cytokeratin (34 beta E12) and CK5/6. They also mark with androgen receptors.

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Reference: Prostate gland & seminal vesicles - Anatomy & histology
Board review style question #2

Thinking about the above image of benign reactive basal cells, what histologic feature is characteristic of a secretory cell but not a basal cell?

  1. Acquiring prominent nucleoli
  2. Nuclear vacuoles
  3. Nuclei may have prominent nuclear grooves
  4. Nucleoplasm is darker purple
  5. Nucleoplasm is lighter blue
Board review style answer #2
D. Nucleoplasm is darker purple. The secretory cells are less metabolically active than basal cells, giving them a more condensed nucleoplasm. Nuclear vacuoles and grooves, however, are more characteristic of basal cells. Answer A is wrong because basal cells can get somewhat prominent nucleoli if they are reactive; in this case, in response to acute inflammation. However, prominent nucleoli in secretory cells signal PIN or cancer.

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Reference: Prostate gland & seminal vesicles - Anatomy & histology
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