EXTRAMEDULLARY MYELOID CELL TUMORS IN ACUTE NONLYMPHOCYTIC LEUKEMIA -A CLINICAL REVIEW

Purpose: To discuss the predisposing risk factors for all forms of ext ramedullary leukemia (EML) and to review the clinical features, progno stic significance, and treatment strategies for primary EML and leukem ia cutis (LC)/granulocytic sarcomas (GS) in the setting of acute nonly mphocytic leukemia (ANLL). Methods: A review of all reports published since 1965 related to all forms of extramedullary leukemia (LC, GS, gi ngival hypertrophy, and meningeal leukemia [ML]). Results: Several fac tors, including chromosomal abnormalities [t(8;21), inv(16)], cell-sur face markers (CD56, CD2, CD4, CD7), French-American-British (FAB) subt ype (M2, M4, M5), blast differentiation and maturation, patient nutrit ional status, age, cellular immune dysfunction, high presenting leukoc yte count, and decreased blast Auer rods, have been associated with a higher incidence of EML. Of 154 published cases of primary EML identif ied, 71 (46%) were initially misdiagnosed. The addition of immunohisto chemical stains can assist in preventing such misdiagnoses and should be included in all atypical lymphoma/carcinoma cases. Only one of the patients (3%) with primary EML did not progress to ANLL in the absence of chemotherapy. In contrast, 66% of patients who received chemothera py for the primary EML never developed ANLL. The prognostic significan ce of EML at presentation and medullary relapse of ANLL is uncertain. isolated extramedullary recurrence of ANLL always heralds bone marrow relapse and should be treated with reinduction chemotherapy. Close cli nical follow-up observation is necessary to insure resolution of EML. Radiation therapy is an effective local treatment for resistant or sym ptomatic EML. Conclusion: Many advances in diagnoses and treatment of EML have been made. Future investigations ore needed to define the cli nical significance of EML in patients with ANLL treated with modern ch emotherapy or bone marrow transplantation.