Pancytopenia with hypercellular bone marrow--a possible paraneoplastic syndrome in carcinoma of the lung: a report of three cases.

Three patients with idiopathic pancytopenia and hypercellular bone marrow who developed carcinoma of the lung within two years of diagnosis are reported. All three patients had macrocytic anemia associated with a megaloblastic marrow in the presence of normal serum vitamin B12 and folic acid levels. Neutropenia with monocytosis, elevated serum muramidase and LAP scores, and increased fetal hemoglobin levels were also found. In all cases Ham's tests were negative with a normal bone marrow karyotype. In all three patients, pancytopenia due to myelodysplasia, a probable preleukemic state, was diagnosed initially prior to the appearance of carcinoma of the lung. One of the patients showed improved leukocyte and platelet counts during chemotherapy, while the other two died before chemotherapy could be administered. In the light of the above findings we suggest that carcinoma of the lung may be the cause of a paraneoplastic syndrome with pancytopenia, particularly in patients with a hypercellular marrow with a normal karyotype.