Others, often less well differentiated, grow rapidly, invade adjacent tissues, spread by metastasis,Īnd unless extirpated at an early stage will kill the host these are malignant tumors. Some, calledīenign, are well differentiated, grow only by expansion with the formation of a capsule, grow slowly, and are dangerous only in terms of position,Īccidental complication, or excessive hormone production. The tumors of any given cell type may show a wide range of difference in structure, mode of growth, rate of growth, and danger to the host. In addition to histogenetic classification, it is of practical value in human oncology to attempt to predict the behavior of a tumor from its morphology. Dunham and Stewart (ġ953) gave a classification of transplantable and transmissible animal tumors. Cloudman (ġ941) presented a histological classification of mouse tumors. Meanwhile in these cases we must settle for noncommittal identifying names.ġ960) illustrated the application of histogenetic classification to both human and animal tumors. Require further histopathological research. The few kinds of tumors in which there is uncertainty regarding the precise tissue of origin It is unlikely that tumor cells acquire new capacities. Foulds (ġ940) concluded that most adult normal cells have a greater capacity for divergent differentiation than was formerly supposed and that The types of histological differentiation found in tumors appear to be inherent in the parent tissues. In most tumors the neoplastic tissue consists of cells of a single type and, with experience, one can readily classify The commonly used and most useful classification of tumors is histogenetic, that is, the tumors are named according to the tissues from which theyĪrise and of which they consist. Tissues, and persists in the same excessive manner after cessation of the stimuli which evoked the change.' Every pathologist can think of exceptionsīut these do not invalidate the general applicability of the definition. A tumor 'is an abnormal mass of tissue, the growth of which exceeds and is uncoordinated with that of the normal Less well known tumors than for the common types which have been extensively reviewed.ġ960) proposed a workable definition for distinguishing true tumors from inflammatory and reparative proliferations, hyperplasias, and Emphasis has been given to the induced tumors of types important in human pathology, More references have been cited for the

Selected tumors that rarely occur spontaneously but are readily induced have been included, particularly tumors that can be inducedīy hormonal imbalance. Some rare types that have occurred spontaneously in mice at The Jackson Laboratory have been includedįor completeness. Of tumors of untreated mice of inbred strains.

Inbred strains and the amount of research interest shown in them, Many less frequent types repeatedly appear as incidental findings in tabulations The tumors of the mouse described in this chapter have been selected primarily on the basis of frequency of occurrence among the available Chapter 27 - Characteristic Tumors PreviousĢ7 Characteristic Tumors 1 Edwin D.

Irregular tissue fragments meaning