Which stain is most helpful to differentiate BPH from prostate adenocarcinoma?

• A. PSA
• B. NKX3.1
• C. AMACR
• D. PSMA

Answer: (C)

This question is about how immunohistochemical stains help tell apart benign prostatic hyperplasia from prostate adenocarcinoma. AMACR is the stain that best distinguishes them because it is commonly overexpressed in prostate cancer while benign prostatic tissue typically lacks it. In practice, cancerous glands show AMACR positivity and often lose the basal cell layer (which is highlighted by basal markers), whereas benign glands in BPH have a preserved basal layer and are AMACR negative. So a positive AMACR result strongly supports carcinoma when evaluating prostatic glands.

PSA labels prostatic epithelium in both benign and malignant tissue, so it doesn’t differentiate. NKX3.1 marks prostatic origin and is usually present in both BPH and cancer, limiting its discriminative value in this context. PSMA can be useful in imaging and some tissue contexts but is not as reliable for distinguishing BPH from adenocarcinoma on routine histology as AMACR.