[Extramedullary leukemia].

Leukemia is primarily a bone marrow disease. Secondary invasion in other tissues usually disappears after a successful remission induction. Leukemic cells may remain in undetectable numbers in gonads and central nervous system (CNS). These sites are shielded from infiltration by cytostatics, this shielding however is far from absolute. Ovarian leukemia is extremely rare, testicular leukemia is relatively rare. Prophylactic measures (radiotherapy, biopsies) are therefore not warranted. In case of testicular leukemia bilateral biopsies, greater than 2000 Rad irradiation and a reinduction treatment are advised. CNS-leukemia-prophylaxis and treatment should be effective, i.e. complete eradication is the goal, but treatment-strategies should aim at minimizing lasting CNS-damage. The type of treatment given should be tailored to the patient: in non high risk ALL prophylaxis without irradiation is feasible, in T-cell-leukemia and NHR-ALL with initial CNS-leukemia a plea is made for craniospinal irradiation in the prophylaxis scheme. The use of Ommayadrains should be considered.