Hyperplasia affects the transition zone; carcinoma affects the peripheral zone
Mnemonic
“Benign hyperplasia is central, carcinoma is peripheral”:
- Benign prostatic hyperplasia arises in the transition zone, around the urethra, which is why it causes obstructive urinary symptoms early
- Adenocarcinoma arises in the peripheral zone in about 70 per cent, which is why it is palpable on rectal examination but causes symptoms late
“BPH obstructs early and is felt late; cancer is felt early and obstructs late.”
On rectal examination: benign hyperplasia is smooth, symmetrical and enlarged with the median sulcus preserved; carcinoma is hard, irregular and nodular with the sulcus lost.
PSA is prostate specific, not cancer specific: it is raised by benign hyperplasia, prostatitis, urinary infection, catheterisation, recent ejaculation, vigorous exercise and rectal examination, so it should be taken before examination and after any infection has settled.
Gleason grading sums the two most prevalent patterns, and prostate cancer characteristically metastasises to bone, producing sclerotic (osteoblastic) lesions, unlike most other tumours.
Expansion
| Benign prostatic hyperplasia | Adenocarcinoma | |
|---|---|---|
| Zone | Transition (central, periurethral) | Peripheral (posterior) |
| Symptoms | Early obstruction | Late; often asymptomatic until advanced |
| Rectal examination | Smooth, symmetrical enlargement | Hard, irregular, loss of median sulcus |
| Premalignant | No | Arises from prostatic intraepithelial neoplasia |
The zonal difference explains almost everything clinically: benign hyperplasia compresses the urethra and presents with lower urinary tract symptoms, whereas carcinoma grows away from the urethra and is silent until it is locally advanced or has metastasised.
Metastasis is characteristically to bone, and uniquely it produces sclerotic (osteoblastic) rather than lytic lesions, classically in the lumbar spine and pelvis via Batson’s vertebral venous plexus.
Gleason grading sums the two most prevalent architectural patterns, and is unusually important prognostically, more so than for most tumours.
PSA is prostate specific but not cancer specific: it rises with benign hyperplasia, prostatitis, urinary retention, instrumentation and even ejaculation, which is the central difficulty in screening.