from Scott D. Fitzgerald writing in Essentials of Veterinary Parasitology:
Parasites may induce a wide variety of pathology in their host tissues. These changes vary from inapparent, to frank necrosis, grossly visible granulomas, and induction of hyperplastic or neoplastic changes in various tissues. The host may exhibit no clinical signs, or develop anemia, hypoproteinemia, weight loss, anorexia, even death. A few simple terms need to be defined before we begin our discussion of pathology. Localized infection refers to a parasitic infection that is limited to a single host tissue or focal areas of a given organ system. While generalized parasitic infection refers to parasites that have widespread migration throughout the host body in many tissues. While we are not going to make the reader a pathology expert, you should understand some basic pathology terms. Necrosis refers to destruction of normal tissue cells and organ architecture resulting in accumulations of cellular debris, fibrin, inflammatory cells, and red blood cells. Granulomatous inflammation is a chronic form of inflammation which is comprised predominantly of mixed mononuclear leukocytes including macrophages, lymphocytes, plasma cells, and sometimes multi-nucleated giant cells. If a granuloma has central zone of necrosis, this is a caseogranuloma. A hyperplastic change involved increased numbers or size of normal tissues, such as thickening of a keratinized layer in the epidermis being known as hyperkeratosis. Neoplastic transformation means that a true neoplasm consisting of a monomorphic population of cells has developed into a microscopic or grossly visible tumor or mass.
Further reading: Essentials of Veterinary Parasitology