The Radiologic Diagnosis of Leukemia and Lymphoma in Children David C. Kushner, Howard J. Weinstein, and John A. Kirkpatrick C ANCER is the most common cause of nontraumatic death under the age of 1.5 yr in the United States.3 Among childhood cancers, leukemia comprises 33% and lymphoma com- prises 1 4%.82 It is the purpose of this presenta- tion to describe those aspects of leukemia and lymphoma that are unique to childhood. LEUKEMIA Clinical Presentation Certain groups of children are at higher risk for developing leukemia than members of the general population. Recognition of these high- risk patients will encourage the radiologist to be sensitive to subtle abnormalities indicative of leukemia. The increased risk of leukemia may be related to the environment or the genetic back- ground of the patient. The role of environment in the induction of childhood leukemia in the U.S. is controversial. However, there are environmental factors that have been proved to be oncogenic in experimen- tal systems or in adult populations, and these are being studied for their effect upon children. Environmental factors that have been postulated in relationship to childhood leukemia include exposure to diagnostic radiation in utero,68 to postnatal diagnostic or war-time radiation,38 to parental and childhood carcinogens,30 and to oncogenic viruses.24,36 There are several clearly identifiable genetic groups of children who appear to have a predis- position to leukemia.4,46 A partial listing of genetic syndromes associated with childhood From the Pediatric Radiology Section, Department of Radiology, Massachusetts General Hospital; the Sidney Farber Cancer Center; and the Department of Radiology, Childrens Hospital Medical Center, Boston, Mass. David C. Kushner, M.D.: Instructor in Radiology; Howard J. Weinstein, M.D.: Assistant Professor of Pedint- rics; John A. Kirkpatrick, M.D.: Professor of Radiology, Harvard Medical School, Cambridge, Mass. Address reprint requests to David C. Kushner, M.D., Pediatric Radiology Section, Department of Radiology, Massachusetts General Hospital, Boston. Mass. 0 1980 by Grune & Stratton, Inc. 0037-I 98X/80/1504-0006$02.00/0 316 leukemia is provided in Table I. The details of these abnormalities can be sought in standard pediatric textbooks. It is exceptionally rare for a pediatrician to discover covert leukemia in a child who is other- wise well. Frequently, the symptoms and signs are nonspecific and suggest a systemic illness of undetermined cause. These include malaise, fatigue, weight loss, anorexia, fever, ecchymosis, and pallor. Commonly, children will complain of pain in the abdomen, back, or extremities. Lymphadenopathy and hepatosplenomegaly are characteristic.‘h,7’ Laboratory investigation frequently reveals thrombocytopenia and aplastic anemia. An elevated leukocyte count with abnormal number and appearance of blast forms in the peripheral smear is very suggestive of leukemia although not diagnostic. The differential diagnosis is difficult because leukemia may imitate the symptoms of virtually any other childhood disease. Leukemic anemia and bleeding may mimic many hematologic disorders, including aplastic anemia and idio- pathic thrombocytopenic purpura. Chronic or acute infection may have systemic and labora- tory components similar to those of leukemia. Acute rheumatic fever, juvenile rheumatoid arthritis, and other connective tissue diseases may mimic the symptoms of leukemia.67 Other malignant tumors that may mimic the skeletal radiographic changes of leukemia include meta- static neuroblastoma, Ewing tumor, and histio- cytoma. Pathology There are several types of childhood leukemia, and these have several clinical presentations and modes of therapy. Because the radiologist is involved in the initial diagnosis, the evaluation of response to therapy, and demonstration of complications, it is important that he understand the basic subtypes of leukemia and therapeutic options that form standard pediatric practice. Leukemia in children is almost always of the acute form. Of these, approximately 70% are histologically classified as lymphoblastic, 20%- Seminars in Roenfganoto~, Vol. XV, No. 4 Kktober), 1980