Surgery MCQs Q7

A 68-year-old man undergoes a routine prostate examination. You want to determine the most common site for carcinoma of the prostate.

Which of the following zones of the prostate is most commonly affected by prostate cancer?

A. Anterior zone

B. Transitional zone

C. Peripheral zone

D. Central zone

E. Posterior zone

✅ Correct Answer:

C. Peripheral zone

🔍 Decoding the Stem

• 💡 CLUE 1: Prostate zones → Prostate is divided into: Peripheral, Central, Transitional, Anterior fibromuscular
• 💡 CLUE 2: Prostate cancer epidemiology → Most carcinomas originate in the Peripheral zone (~70–80%)
• 💡 CLUE 3: Usually posterolateral aspect, palpable on digital rectal exam

Why Peripheral Zone is Correct

Peripheral zone makes up the largest portion of the prostate (~70%). Located posteriorly and laterally, near the rectal wall → accessible on DRE. Most adenocarcinomas arise here. Early cancer often asymptomatic, sometimes detected via DRE or PSA screening.

Why Other Options Are Incorrect

A. Anterior zone: Mostly fibromuscular stroma. Rarely develops carcinoma.

B. Transitional zone: Site of BPH. Only ~20% of cancers arise here.

D. Central zone: Surrounds ejaculatory ducts. Rare site for malignancy (~5%).

E. Posterior zone: Posterior aspect is part of peripheral zone, but the term “posterior zone” is not anatomically distinct. Peripheral zone includes posterior and lateral regions.

🧠 High-Yield Points

Most common site of prostate carcinoma → Peripheral zone
BPH → Transitional zone
DRE findings → Nodules or asymmetry in peripheral zone should raise suspicion for cancer
PSA >10 ng/mL → with nodular peripheral zone → strong malignancy suspicion

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💡 Quick Clinical Challenge:

A patient with a very high PSA has a normal feeling DRE. The clinician suspects a tumor in a region not easily reachable by finger.

Your Challenge:

1. Which zone is most associated with urinary obstruction in Benign Prostatic Hyperplasia (BPH)?
2. What imaging modality is best for guided prostate biopsy?

Show Answer

✅ Answer:

1. Transitional Zone.
2. Transrectal Ultrasound (TRUS).