An earlier study conducted by Netea-Maier et al. (2008) by examining differences of protein abundances between follicular adenoma and follicular cancer tissues has also shown a statistically significant difference in the levels of PDI, which is one of 20 proteins belonging to a family of enzymes that mediate oxidative protein folding in the endoplasmic reticulum (Kozlov et al., 2010). The gene discussed is P4HB; the disease is follicular thyroid adenoma.