Tumors of the mouse hematopoietic system: their diagnosis and interpretation in safety evaluation tests. Report of a study group.

A nomenclature for tumors of the mouse hematopoietic system is proposed. This nomenclature, which will be particularly appropriate for use in safety assessment studies, employs basic cytologic terminology, and subclassifications may take into consideration tissue sites and the presence or absence of leukemia. Analysis of tumor incidence in any given study can take into account the consolidation or separation of various tumor types as pathological and biological judgment indicates. The proposed system should be easily understood by pathologists and can be related to other species. Safety assessments of substances that induce tumors of the murine hematopoietic tumors are complicated by difficulty in diagnosis, by the possible involvement of oncogenic viruses, and by other factors such as genetics, immune status, endocrine status, and diet. These various influences are evaluated in respect to interpretation of safety evaluation data.