Orbital myeloid sarcoma in an adult with acute myeloid leukemia, FAB M1, and 12p-deletion.

A 49-year-old woman with acute myeloid leukemia, FAB M1 subtype, and 12p deletion, presented with progressive right proptosis and diplopia for 1 week. Orbital CT revealed a homogenously enhancing, orbital mass engulfing the inferior rectus muscle. Histopathology revealed myeloid sarcoma for which she underwent external beam radiotherapy. Subsequently, there was no sign of local recurrence, but she succumbed to leukemia involving the central nervous system. This is the first case, to the authors' knowledge, of an orbital sarcoma of FAB M1 myeloblasts bearing a 12p deletion.