TETRASOMY-8 IN ACUTE MONOBLASTIC LEUKEMIA (AML-M5A) WITH MYELOSARCOMATOSIS OF THE SKIN

We report a new case with isolated tetrasomy 8, an 82-year-old female patient in whom multiple disseminated nodular skin infiltrations up to 5 cm in diameter preceded mute monoblastic leukemia (AML-M5a). Despit e an initial response to chemotherapy and radiotherapy, the patient di ed 1 year after diagnosis of relapsed leukemia. To assess the size of the tetrasomic clone, fluorescence in situ hybridization (FISH) analys is with a centromere-specific chromosome 8 probe was performed. Sevent y percent of interphase cells showed four signals and 22% showed three signals. Because this trisomic clone was not detected by conventional cytogenetics, tetrasomic cells may have a proliferation advantage in vitro. Whether tetrasomy 8 arises from a simultaneous mitotic nondisju nction of both chromosomes 8 during one cell division or evolves secon darily from trisomy 8 through a second mitotic error is not known. Alt ernatively trisomy 8 may originate from tetrasomy 8 by loss of one chr omosome 8.