Tumors of the hematopoietic and lymphoid tissues (American English) or tumours of the haematopoietic and lymphoid malignancies (British English) are tumors that affect the blood, bone marrow, lymph, and lymphatic system.Because these tissues are all intimately connected through both the circulatory system and the immune system, a disease affecting one will often affect the others as well, making myeloproliferation and lymphoproliferation (and thus the leukemias and the lymphomas) closely related and often overlapping problems.
While uncommon in solid tumors, chromosomal translocations are a common cause of these diseases. This commonly leads to a different approach in diagnosis and treatment of haematological malignancies.
Haematological malignancies are malignant neoplasms ("cancer"), and they are generally treated by specialists in hematology and/or oncology. In some centers "haematology/oncology" is a single subspecialty of internal medicine while in others they are considered separate divisions (there are also surgical and radiation oncologists). Not all haematological disorders are malignant ("cancerous"); these other blood conditions may also be managed by a hematologist.
