Extramedullary acute promyelocytic leukemia.
Extramedullary acute promyelocytic leukemia (APL) is rare, and said to be more common after treatment with all-trans retinoic acid (ATRA) than after any other treatment. The case of a child with extramedullary relapse of APL after initial treatment with ATRA and that of an adult whose initial treatment was chemotherapy are presented, and the literature on extramedullary relapse of APL is reviewed. Twenty-six patients were identified, including the 2 current patients. Ethnicity could be determined in 23 patients, 17 of whom were of other than Northern European extraction. The most common sites of extramedullary disease were the skin (15 patients), central nervous system (5 patients), mediastinum (3 patients), and, curiously, gingiva (3 patients). Extramedullary leukemia developed in 19 patients: after treatment with ATRA (6 patients), cytotoxic chemotherapy (12 patients), or both (1 patient), and developed in 7 others before any treatment for leukemia was given. These data suggest but do not prove that extramedullary APL may occur more frequently after ATRA than other therapy, since ATRA has been available for a relatively short period of time. However, it is clear from the literature that extramedullary APL may occur after chemotherapy or before any treatment.