Features:

Four prostate glands at different stages of disease progression

■Stage 1: benign, slightly enlarged, but still a normal gland

■Stage 2: a well-defined, hard nodule can be felt in the right upper quadrant of the gland, simulating the early stages of prostate tumor development.

■Stage 3: the tumor has spread within the gland and the original small nodule has developed into a mass.

■Stage 4: the gland is completely replaced by the tumor, and the surface of the gland is uneven and hard.