mesothelioma

Leukemia is a form of cancer that affects blood or bone marrow and is marked by abnormal proliferation of blood cells, typically leukocytes (white blood cells). The term "leukemia" is a general and encompassing word used to describe four disease-types, know as acute myelogenous leukemia, acute lymphocytic leukemia, chronic myelogenous leukemia, and chronic lymphocytic leukemia.

The term "lymphocytic" indicates cancerous activity is occurring in a type of marrow cell that forms lymphocytes, and the term "myelogenous" indicates cancerous changes are taking place in a type of marrow cell that forms red cells, some white cells, and platelets.

The difference between acute and chronic leukemias lies in the presence of blast cells and the speed of progression. Acute leukemias tend to progress quickly without treatment and blast cells are present. Chronic leukemias have very few or no blast cells and progression is slower in comparison to acute leukemias. All leukemias, as well as lymphomas and multiple myeloma, are considered hematological malignancies (types of cancer that affect blood, bone marrow, and lymph nodes).

The first studies to document a connection between hematological malignancies and exposure to asbestos were published in the late 1970s and early 1980s. In a study titled "Asbestos-associated neoplasms of B cell lineage" (1979), six cases of chronic lymphocytic leukemia were reported in patients with a history of asbestos exposure.

Another study titled "Acute myelocytic leukemia after exposure to asbestos" (1988) reported on two cases of acute myelogenous leukemia in two people with an extended history of exposure to asbestos. This study found significant amounts of asbestos in lung and bone marrow specimens of the two patients. The type of asbestos observed was crocidolite asbestos, which is considered to cause cancer more readily than many other asbestiform minerals. In another study by the same authors, which analyzed the relationship between malignancy and asbestos exposure, five out of 10 cases of leukemia were related to asbestos exposure.

In a more recent study published in 2005, a patient with a strong history of heavy asbestos exposure developed B-prolymphocytic leukemia/lymphoma (B-PLL) and then quickly developed malignant peritoneal mesothelioma. The study noted the concurrent development of these two uncommon diseases implied the possibility of a causative factor. Upon ruling out other plausible factors, the authors concluded that asbestos exposure was the sole possible connection to these malignancies.

The underlying principle for the association between asbestos and lymphoid neoplasms is the ability of asbestos fibers to reach the lymph nodes and other elements of the immune system. Some studies have experienced difficulty in finding evidence of a relationship between asbestos exposure and the development of leukemia, and as such, further analysis is needed to better understand this plausible relationship.

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