A Case of Ectopic CD7(+) Congenital Monocytic Leukemia

ABSTRACT

Congenital acute leukemia is a rare disorder with approximately 200 cases reported. It is defined as a childhood leukemia occurring at birth or before 1 month of age at a rate of 1%. Acute leukemias are generally classified according to morphology, cytochemistry and cell surface marker expression. Most leukemias conform to an ordered lineage-specific pattern of gene expression, but a small subset of leukemias appears not to follow lineage restriction. Several reports revealed a subgroup of acute myelogenous leukemia(AML) that expresses CD7, a cell surface marker expressed early during T lineage differentiation, especially in less differentiated AML subtypes. We report a rare case of CD7(+) congenital monocytic leukemia(M5a) with detailed immunophenotypic and cytochemical characterization in an 8 week-old female. She had central nervous system (CNS) involvement at diagnosis. Chromosomal analysis revealed a mosaicism with 46,XX,-6,de1(7) (q21),t(19;21)(q13.3;q22)/46,XX, that has not been reported.