The bulk of this book is concerned with anatomic pathology. Certain terms related to this field deserve clarification here. HISTOLOGY is a division of anatomy concerned with the microscopic study of tissues. MICROSCOPIC ANATOMY applies the materials and methods of histology to specific organs and bodily structures. CYTOLOGY is the study of cells. HISTOPATHOLOGY refers to the study of microscopic changes in tissue induced by disease or injury. HISTOCHEMISTRY is a specialized field in which chemical properties and reactions of tissues are observed microscopically. ELECTRON MICROSCOPY is the study of specimens with an electron microscope, which uses a stream of electrons instead of a beam of visible light and allows much greater magnification than the light microscope used for routine lab work. The term HISTOLOGY is often applied to the whole range of lab techniques used in preparing slides of tissue specimens for microscopic study by a pathologist. CYTOLOGY is often used in the narrow sense of a study of cells that have been detached from a surface for microscopic study, as in a Pap smear. The pathologist's report of an autopsy or of examination of a tissue specimen is customarily dictated for subsequent transcription. In reporting the findings, a pathologist ordinarily describes not only the abnormal features of the specimen but also identifying anatomic characteristics, gross and microscopic. Having described his gross and microscopic findings, the pathologist usually records a diagnosis or diagnostic impression, summarizing and coordinating those findings in the light of his specialized knowledge and experience. The diagnoses listed at the end of an autopsy report may number ten, twenty, or more. The diagnoses may be accompanied by code numbers referring to some standard system of disease nomenclature. If malignant the pathologist diagnosis often includes an estimate of the extent of the malignant process according to a standard grading or staging system.