Chronic mast cell leukemia: A novel leukemia-variant with distinct morphological and clinical features

•Mast cell leukemia (MCL) is a rare fatal form of a mast cell disease.•Based on the presence of organ damage, MCL is classified into acute MCL and chronic MCL.•The variant of MCL correlates with the prognosis and with the morphology of mast cells.

SummaryMast cell leukemia (MCL) is a rare form of systemic mastocytosis characterized by leukemic expansion of mostly immature mast cells, organ damage, drug-resistance, and a poor prognosis. Even when treated with chemotherapy, most patients have a life-expectancy of less than one year. However, there are rare patients with MCL in whom the condition is less aggressive and does not cause organ damage within a short time. In these patients, mast cells exhibit a more mature morphology when compared to acute MCL. A recently proposed classification suggests that these cases are referred to as chronic MCL. In the present article, we discuss clinical, histopathological and morphological aspects of acute and chronic MCL.