Introduction

Our first task is to provide you with a working knowledge of the pathologic terms and concepts used throughout the text. This chapter defines terminology, compares and contrasts malignant and benign tumors, considers characteristics and behavior of malignant cells, and discusses how invading malignancies kill an individual. Tumors, with time, undergo changes that lead to autonomy. This progression of events is also examined.

An appreciation of embryology leads to a consideration of the origin of stem cells and the concepts of determination and differentiation. Both are important to understanding the origin of cancer cells, and such comprehension may lead to new modalities for treating cancers. Most textbooks of cancer biology begin with a discussion of cells. But we start with an examination of what cancer is to help you get a better grasp of the material that follows. Metastasis is difficult to understand without a prior foundation in the concepts of pathology. Similarly, carcinogenesis or chemotherapy is incomprehensible without knowledge of what a malignant cell is and how it behaves.

Much of our knowledge about tumors dates from antiquity. The streaks of hard gray tissue that extend from a tumor into the normal tissues reminded the Ancients of a crab, so they named the condition cancer (from the Greek word meaning crab). The term “tumor” denotes a mass, whether neoplastic, inflammatory, pathologic, or even physiologic. Today, tumor is used generically to describe any neoplasm, irrespective of its origin or biologic behavior.