Natural killer lymphoma/leukemia: an uncommon pediatric case with indolent course.

Natural killer (NK) cell lymphomas are rare in the USA and Europe but more common in Asia and Central America although very rare among children. We report a case of Epstein-Barr virus-positive NK lymphoma/leukemia, that showed peculiar features represented by a very long clinical course with a significant interval between the first clinical signs and the diagnosis, detection of neoplastic cells in the peripheral blood but not in the bone marrow, and good response to treatment and clinical outcome.