Table 1.

Classification of p16, pRb, and p53 immunohistochemistry staining.

Protein	Absent to Low	Moderate	High
p16	<20% of cancer cells have low cytoplasmic intensity	20%–50% of cancer cells have low to intermediate cytoplasmic and nuclear staining intensity	>50% of cancer cells have high cytoplasmic and nuclear staining
pRb and p53	<20% of cancer cells have low to intermediate nuclear staining intensity	20%–50% of cancer cells have high nuclear staining intensity, or >50% of cancer cells have low to intermediate nuclear staining intensity	>50% of cancer cells have high nuclear staining intensity