Benign Prostatic Hyperplasia

Overview

BNH/BEP = common, non-neoplastic, tumour-like prostate enlargement — arguably normal ageing. ↑with age, 75-80% by 80yr, but only 5-10% symptomatic enough for surgery.

Pathophysiology

Endocrine hypothesis best supported. Both sexes make androgen+oestrogen (androgen dominant males). Advancing age: ↓androgen, ↑oestrogen (relative) in men. KEY: periurethral INNER prostate (BEP site) = oestrogen-responsive; OUTER prostate (carcinoma site) = androgen-responsive — explains why BPH+cancer arise in different zones, largely independent processes despite both age-related. Mechanism: synergistic stimulation — oestrogen sensitises tissue to DHT’s growth-promoting effect.

Morphology

Gross: enlarged, nodular, smooth, firm, 2-4x normal weight (40-80g). Cut surface: glandular-predominant (yellow-pink, soft, honeycombed, milky exudate) vs fibromuscular-predominant (firm, homogeneous, no exudate). Mass in INNER PERIURETHRAL gland → false capsule (surgical enucleation basis). Peripheral leftover tissue may recur or → carcinoma later.

Micro: hyperplasia of all 3 elements (glandular/fibrous/muscular), varying proportions.

• Glandular (usual predominant) — exaggerated intra-acinar papillary infoldings, delicate fibrovascular cores, TWO-LAYERED epithelium (inner tall columnar mucus-secreting + outer cuboidal/flat basal-nuclei layer)
• Fibromuscular (when dominant) — spindle cell aggregates, resembles uterine fibromyoma
• Also: lymphocytic aggregates, small infarcts, corpora amylacea, squamous metaplasia foci

Clinical features

Symptoms from URETHRAL OBSTRUCTION cascade: bladder (hypertrophy, cystitis) → ureter (hydroureter) → kidney (hydronephrosis). Presenting: frequency, nocturia, difficulty voiding, pain, haematuria; sometimes ACUTE RETENTION requiring catheterisation.

Clinical relevance

Zone-specific hormone responsiveness (periurethral/oestrogen=BPH vs peripheral/androgen=carcinoma) = single most important organising fact — explains coexistence without causation, why BPH isn’t a significant carcinoma precursor despite superficial plausibility. False capsule around hyperplastic nodule = direct anatomic basis for enucleation surgical technique (open/TURP) — exploits plane between hyperplastic and compressed peripheral tissue. Obstruction→hydronephrosis cascade = single upward-propagating sequential process (urethral obstruction→bladder→ureter→kidney), not 4 separate complications — same principle for any distal urinary obstruction. BEP+incidental carcinoma on prostatectomy specimen = concurrent independent ageing pathology in different zones, NOT one disease progressing to the other.

Overview

Benign nodular hyperplasia (BNH)/benign enlargement of prostate (BEP) is a very common, non-neoplastic, tumour-like enlargement of the prostate — arguably a normal ageing process in men. Frequency rises sharply with age, reaching 75–80% by age 80, though only 5–10% become symptomatic enough (urinary obstruction) to need surgery.

Pathophysiology

Cause not fully established, but the endocrine hypothesis is best supported. Both sexes produce androgen and oestrogen (androgen dominant in males, oestrogen in females); with advancing age, androgen levels decline while oestrogen correspondingly rises in men. Critically, the two prostatic zones respond to different hormones: the periurethral inner prostate (site of BEP) is oestrogen-responsive, while the outer prostate (site of carcinoma) is androgen-responsive — this anatomic-hormonal split is why BPH and prostate cancer arise in different zones and are largely independent processes despite both increasing with age. Proposed mechanism: synergistic stimulation — oestrogen sensitises prostatic tissue to the growth-promoting effect of dihydrotestosterone derived from plasma testosterone.

Morphology

Gross: enlarged prostate, nodular, smooth, firm, 2–4× normal weight (up to 40–80 g). Cut surface varies by composition: glandular-predominant BEP is yellow-pink, soft, honeycombed, exudes milky fluid; fibromuscular-predominant BEP is firm, homogeneous, no milky exudate. The hyperplastic mass forms mainly in the inner periurethral gland, leaving surrounding tissue as a false capsule — the surgical basis for enucleation. Left-over peripheral tissue may later undergo recurrent hyperplasia or develop carcinoma.

Micro: hyperplasia of all three tissue elements (glandular, fibrous, muscular) in varying proportions.

• Glandular hyperplasia (usual predominant pattern) — exaggerated intra-acinar papillary infoldings with delicate fibrovascular cores; two-layered epithelium — inner tall columnar mucus-secreting cells (poorly-defined borders) over an outer cuboidal-to-flattened layer with basal nuclei.
• Fibromuscular hyperplasia (when dominant) — spindle cell aggregates resembling uterine fibromyoma.
• Additional common findings: lymphocytic aggregates, small infarction foci, corpora amylacea, squamous metaplasia foci.

Clinical Features

Symptomatic disease arises from urethral obstruction and its downstream effects — bladder (hypertrophy, cystitis), ureter (hydroureter), kidney (hydronephrosis) — a direct anatomic cascade up the urinary tract (see Hydronephrosis). Presenting features: frequency, nocturia, difficulty voiding, pain, haematuria; sometimes acute urinary retention requiring immediate catheterisation.

Clinical Relevance

• The zone-specific hormone responsiveness (periurethral/oestrogen-driven BPH versus peripheral/androgen-driven carcinoma) is the single most important organising fact in this topic — it explains both why the two conditions can coexist in the same ageing prostate without one causing the other, and why BPH is generally not considered a significant carcinoma precursor despite the superficial plausibility of that idea.
• The false capsule formed around the hyperplastic periurethral nodule is not just a histologic curiosity — it is the direct anatomic basis for the surgical technique of enucleation (as in open or transurethral prostatectomy for BPH), where the plane between hyperplastic tissue and compressed peripheral tissue is exploited to remove the obstructing mass.
• The obstruction-to-hydronephrosis cascade (urethral obstruction → bladder hypertrophy/cystitis → hydroureter → hydronephrosis) is a direct, sequential anatomic consequence worth understanding as a single upward-propagating process rather than four separate complications — this is the same principle governing any distal urinary obstruction, not something unique to BPH.
• Recognising that BEP and prostate cancer typically originate in different prostatic zones is clinically important when interpreting a prostatectomy specimen for BEP that incidentally reveals carcinoma — this reflects concurrent, independent ageing-related pathology in two different zones, not one disease progressing into the other.

• Zone-specific hormone responsiveness: periurethral/oestrogen-driven BPH vs peripheral/androgen-driven carcinoma
• Obstruction cascade: urethra → bladder → ureter → kidney