non-Lymphoid neoplasias myeloid hyperplasia Hyperplasia of myeloid lineage, usually in the spleen. MPATH:618 Myeloid hyperplasia ia a common diagnosis in mouse spleen. In the normal mouse spleen, a low degree of production of myeloid cells occurs (neutrophils, erythroid cells and megakaryocytes). Commonly in aging mice, due to tumors and inflammatory lesions, the mouse myeloid system in bone marrow and spleen react and become hyperplastic. In the spleen it is diagnosed as "myeloid hyperplasia" (MH), in the past it was often extramedullary hematopoiesis, which is still used by some but it is normal to a low degree in normal mouse spleen. mouse_pathology.ontology