Basing on different degrees of prostate carcinoma, we design four interchangeable prostates:

1. Benign, slightly enlarged, but normal prostate gland simulates benign stage.

2. Prostate with two discreet, hard nodules (one is at left lobe; the other is at right lobe) simulate beginning stage.

3. Prostate with easily palpable large mass simulate intermediate stage. The small nodule has increased in size and has become an external hard mass on the surface of the gland.

4. Prostate with malignant invasive cancer simulate terminal stage. This gland is totally replaced with carcinoma. The entire gland will feel hard and irregular.