1. Transmission electron micrograph (TEM) of a normal blood lymphocyte. 2. Scanning electron micrograph (SEM) of a normal blood lymphocyte. 3. TEM of Sézary cell in a patient with the erythrodermic type of cutaneous T-cell lymphoma. Note the cell's characteristic profoundly misshaped (cerebriform) nucleus. 4. TEM of a hairy cell. Arrow indicates a ribosome-lamella complex. This structure is not specific for hairy cell leukemia but is found in a variable proportion of hairy cells in about 50 percent of cases examined by TEM. Frequent cytoplasmic membrane, "hairy," projections. 5. TEM of plasmablast (undifferentiated myeloma cell). Arrow points to a Russell body. 6. A lymphoblast from the marrow of a patient with acute lymphoblastic leukemia. Very high nuclear-to-cytoplasmic ratio. Prominent nucleolus. The nucleus is virtually all euchromatin (likely transcriptionally active). (Reproduced with permission from Lichtman's Atlas of Hematology, www.accessmedicine.com.)