Often students will fixate on one morphological criteria, and use this one criteria to arrive at a diagnosis. However, we teach them that only one criteria does not make a diagnosis. We need multiple criteria, and multiple cells to make a definitive diagnosis. My analogy to them would be that diagnosis is akin to following a recipe. For example baking a cake requires multiple ingredients. Although flour may be a necessary component, it is not the only ingredient required. Other ingredients are necessary to bake a cake successfully.