Anemia is characterized by a decrease in the number of red blood cells or hemoglobin. Histologically, different types of anemia can present distinct features. For example, in iron deficiency anemia, red blood cells appear smaller (microcytic) and paler (hypochromic). In megaloblastic anemia, due to vitamin B12 or folate deficiency, red blood cells are larger (macrocytic) with an increased mean corpuscular volume (MCV).
