Bone marrow examination has become increasingly important for the diagnosis and treatment of hematologic and other illnesses. Morphologic evaluation of the bone marrow aspirate and biopsy has recently been supplemented by increasingly sophisticated ancillary assays, including immunocytochemistry, cytogenetic analysis, flow cytometry, and molecular assays. With our rapidly expanding knowledge of the clinical and biologic diversity of leukemia and other hematologic neoplasms, and an increasing variety of therapeutic options, the bone marrow examination has became more critical for therapeutic monitoring and planning optimal therapy. Sensitive molecular techniques, in vitro drug sensitivity testing, and a number of other special assays are available to provide valuable data to assist these endeavors. Fortunately, improvements in bone marrow aspirate and needle technology has made the procurement of adequate specimens more reliable and efficient, while the use of conscious sedation has improved patient comfort. The procurement of bone marrow specimens was reviewed in the first part of this series. This paper specifically addresses the diagnostic interpretation of bone marrow specimens and the use of ancillary techniques.

Erythrocytes appear in large numbers in the lymph of rats and dogs after massive exposure to x rays. The peak of endothelial fragility, as indicated by the erythrocyte counts in the lymph, is reached on the ninth to fourteenth day in rats and the eleventh to seventeenth day in dogs. In both species the erythrocyte count in the lymph frequently exceeds one million. Diversion of erythrocytes into the lymph compartment causes a relative anemia; excessive destruction of erythrocytes, presumably related to extravasation and not to a direct irradiation injury, is responsible in part for the absolute anemia. It is suggested that similar changes may contribute to the anemia of leukemia and other blood diseases associated with capillary fragility. The drop in lymphocyte counts in both lymph and blood is precipitous within 5 to 10 hours after irradiation. During the fourth to eighth hours after irradiation, injured and dead lymphocytes are present in the lymph in large numbers. During the recovery phase, the per cent of large lymphocytes in the lymph greatly increases, there are many abnormal large lymphoid cells and mitotic figures, and tissue mast cells appear in blood smears. It is concluded that diversion of erythrocytes into the lymph caused by massive irradiation, if severe, becomes a self-aggravating process and leads to death.