A 65-year-old man undergoes transurethral resection of prostate (TURP) for benign prostatic hyperplasia. Histopathology shows nodular hyperplasia of glandular and stromal elements. Which single feature best distinguishes benign prostatic hyperplasia (BPH) from prostatic adenocarcinoma?

Explanation

## Distinguishing BPH from Prostatic Adenocarcinoma ### Key Pathological Differences **Key Point:** The hallmark discriminator between BPH and adenocarcinoma is the **presence or absence of invasion through the basement membrane**. BPH is confined within the glandular architecture; cancer breaches this boundary. ### Comparative Features | Feature | BPH | Adenocarcinoma | |---------|-----|----------------| | **Basement membrane** | Intact, preserved | Disrupted, invaded | | **Growth pattern** | Nodular, circumscribed | Infiltrative, ill-defined | | **Nuclear features** | Normal to mild enlargement | Marked enlargement, coarse chromatin, prominent nucleoli | | **Mitotic activity** | Low, normal mitoses | High, abnormal mitotic figures | | **Capsule** | Often present | Absent or incomplete | | **Stromal invasion** | No invasion | Invasion into surrounding tissue | ### Why Invasion is the Best Discriminator **High-Yield:** Invasion through the basement membrane is the **defining criterion of malignancy** in prostatic pathology. This single feature separates benign from malignant disease more reliably than any other finding. **Clinical Pearl:** On histology, adenocarcinoma shows: - Loss of the normal glandular architecture - Infiltration of cancer cells into the surrounding stroma - Disruption of the basement membrane (highlighted by immunostains for collagen IV or laminin) - BPH, by contrast, maintains organized nodules with intact basement membranes **Mnemonic: INVASION = Cancer** - **I**nfiltration through basement membrane - **N**uclear atypia (secondary finding) - **V**iolation of normal architecture - **A**bnormal mitoses (secondary finding) - **S**tromal infiltration - **I**ll-defined borders - **O**rganized nodules (BPH, NOT cancer) - **N**ucleoli prominent (in cancer) ### Why Other Options Are Incorrect While BPH nodules often have a capsule and adenocarcinoma typically lacks one, this is a **secondary feature** and not as reliable as basement membrane invasion. Nuclear enlargement and abnormal mitoses are important but can occasionally be seen in atypical hyperplasia or reactive changes. Invasion through the basement membrane is the **gold standard** discriminator. [cite:Robbins 10e Ch 20]