Introduction to Hematologic Neoplasms

General

hematologic neoplasms account for ~7% of new neoplasms and 8% of cancer deaths

important because they make up a large proportion of cancer deaths in children and young adults

provide good prototype for cancer study because these cells are relatively easy to isolate and culture

result from monoclonal expansion of any of the hematologic precursors (almost all have a normal cell counterpart)

Myeloid Stem Cell Disorders - the big picture

(1) aplastic anemia
(2) myelodysplastic disorder: a pre-malignant condition (like Barret’s esophagus); used to be called ‘pre-leukemia’
(3) myeloproliferative disorders: includes CML, also proliferative diseases of RBC and platelets
any of these can evolve into AML (including aplastic anemia)

Lymphoproliferative Disorders - the big picture

(1) Hodgkin’s disease: was the prototype for treatment of lymphomas
(2) non-Hodgkin’s lymphomas: many different subtypes
(3) lymphoid leukemias
(4) plasma cell dyscrasias: malignancies arising from plasma cells; multiple myeloma is the prototype

Leukemias – arise from transformation of a single stem cell within the bone marrow Þ monoclonal

primary expansion is in the marrow; this leads to suppression of normal hematopoiesis (the abnormal cells may not grow any faster than normal, but they lack contact inhibition so they can overrun the normal cells)

they can be released into the blood and secondarily expand in any organ; commonly invade lymphatic tissue resulting in lymphadenopathy and splenomegaly, or bone marrow failure

specific chomosomal abnormalities allow classification and may explain some of the neoplastic behavior

classified based on cell of origin (myeloid vs. lymphoid); clinical behavior, and state of differentiation (acute vs. chronic)

Þ this results in four major classes: AML; ALL; CML; CLL

acute: rapid onset; cells are more immature; survival is short without treatment

chronic: cells have more mature characteristics; survival is often long even without therapy

Lymphomas – arise from transformation of a lymphoid precursor in the periphery (most often lymph nodes)

bone marrow may become involved secondarily (called leukemic phase)
majority are classed as non-Hodgkin’s lymphoma: many subtypes that arise from a different stage in lymphoid development with retention of some characteristics of the cell of origin
considerable overlap with lymphoid leukemias

Treatment of Hematologic Malignancies

supportive care is one of the most important factors in survivial: patients are susceptible to infection, so need antibiotics; myelosuppression means they may need a lot of blood transfusions, etc.

chemo: the mainstay of treatment

radiation: effective in reducing the size of mass lesions

marrow transplant