Metaplasia Metaplasia is an adaptive change in which one adult (mature) cell type is replaced by another adult (mature) cell. In this differentiation is not lost, rather it changes from one lineage to another, i.e. stems cell differentiates along a new pathway. But, the resulting cells are fully mature and differentiated. It is reversible. There is no pleomorphism, and cell polarity as well as cell & nuclear size are not altered. Dysplasia Dysplasia means disordered (abnormal) growth ---> there is disordered differentiation and maturation. This generally consists of an expansion of immature cells, with a corresponding decrease in the number and location of mature cells there is loss of uniformity of individual cells. Dysplastic cells show following feature Loss of polarity Hyperchromatosis Increased nuclear cytoplasmic size ratio (normal 1:4 to 1:6). Pleomorphism Increased number of mitosis with normal pattern. Dysplasia is parially reversible, i.e. It is reversible in early stage and later on it is irreversible. Term Dysplasia is usually used, when these changes occur in epithelium. When dysplastic changes involve the entire thickness of epithelium, it is concidered as preinvasive lesion and is referred to as carcinoma in situ. Anaplasia Anaplasia means lack of differentiation. That means anaplastic cells resemble primitive appearing, unspecialized (undifferentiated) cells. o Anaplasia is seen only in malignancy. Anaplastic cell shows - Loss of polarity Hyperchromatasia Increased nuclear cytoplasmic cell ratio Pleomorphism Increased number of mitosis which is atypical Anaplasia is irreversible.