What is the fine-grained topic of the following text: Missense mutations of JAK3 have been described in approximately 34% of T cell prolymphocytic leukemias, 20% of natural killer cell lymphoma, 10% of T cell acute lymphoblastic leukemia including early T cell precursor T cell ALL and occasional cases of Down syndrome associated -myeloid leukemia, -transient leukemia and -acute megakaryoblastic leukemia. Only return the topic.
Missense mutations of JAK3 in various types of leukemia