Congenital monoblastic leukemia with 9;11 translocation in monozygotic twins: A case report

We report an autopsy case of congenital monoblastic leukemia that developed in monozygotic twins. The twin presented with progressive hepatosplenomega ly at 4 weeks after birth. One twin died of massive bleeding and hypovolemi c shock before the treatment started. At autopsy, the liver was diffusely e nlarged and showed a diffuse whitish discoloration except for the subcapsul ar and perivenular areas. Microscopic examination disclosed infiltration of histiocyte-like atypical cells along the sinusoids and portal areas of the liver. Spleen, lymph nodes and choroid plexus were also infiltrated by the tumor cells. However, bone marrow involvement of the tumor was minimal alt hough multifocal. On immunohistochemical staining, these atypical cells wer e reactive for CD68 (PGM-1) and lysozyme, suggesting that the tumor cells m ight have been derived from monohistiocyte. Cytogenetic study revealed 9;11 translocation, which is frequently associated with acute monoblastic leuke mia. To the best of our knowledge, this is the first report of congenital m onoblastic leukemia of monozygotic twins in Korea.