Hematological malignancy

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. As those elements 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. Hematological malignancies may derive from either of the two major blood cell lineages: myeloid and lymphoid cell lines. The myeloid cell line normally produces granulocytes, erythrocytes, thrombocytes, macrophages and mast cells; the lymphoid cell line produces B, T, NK and plasma cells. Lymphomas, lymphocytic leukemias, and myeloma are from the lymphoid line, while acute and chronic myelogenous leukemia, myelodysplastic syndromes and myeloproliferative diseases are myeloid in origin. A subgroup of them are more severe and are known as haematological malignancies (British English)/hematological malignancies (American English) or blood cancer. They may also be referred to as liquid tumors. For the analysis of a suspected hematological malignancy, a complete blood count and blood film are essential, as malignant cells can show in characteristic ways on light microscopy. When there is lymphadenopathy, a biopsy from a lymph node is generally undertaken surgically. In general, a bone marrow biopsy is part of the 'work up' for the analysis of these diseases. All specimens are examined microscopically to determine the nature of the malignancy. A number of these diseases can now be classified by cytogenetics (AML, CML) or immunophenotyping (lymphoma, myeloma, CLL) of the malignant cells. Historically, hematological malignancies have been most commonly divided by whether the malignancy is mainly located in the blood (leukemia) or in lymph nodes (lymphomas).