ANDREAS C. LAZARIS
Neoplasia is characterized by uncontrolled cellular growth owing to increased cellular proliferation and/or decreased apoptosis. If the neoplasm grows without invading its stroma and surrounding tissues ,it is of benign nature and the disease is local. If the growing neoplasm invades its stroma and surrounding tissues gaining access to lymph vessels or blood vessels, it acquires metastatic potential so the disease is potentially systemic, not only local. When we examine all neoplasms microscopically, we look for signs of differentiation ie, their resemblance to normal tissues so as to define their histogenesis and classify them , since the tissue towards which a neoplasm differentiates is generally identical to the tissue from which it derives. Only in malignant tumours, the degree of differentiation is reported as the histologic grade of malignancy. In benign tumors which are not fully differentiated and exhibit some degree of cellular atypia , we grade their degree of cellular dysplasia. Benign tumors are not staged since, due to their benign nature , they are incapable of metastasizing . On the contrary, malignant tumours are staged according to the extent of their dissemination at the time of their diagnosis.