Figure 2. Immunohistochemical staining of aldehyde dehydrogenase 1 (ALDH1) protein. (A) ALDH1 was expressed as 0, negative (IHC stain, ×200). (B) ALDH1 was expressed as 1+, weakly positive (IHC stain, ×400). (C) ALDH1 was expressed as 2+, intermediate positive (IHC stain, ×200). (D) ALDH1 was expressed as 3+, strongly positive (IHC stain, ×200).