A case conference of hematological malignancies based on the morphology of blood cells was held as a Joint Symposium of the Japanese Society of Laboratory Medicine and Japanese Society of Laboratory Hematology. This style of joint symposium was held four times from 2012 to 2016, whereas child cases were presented for the first time this year. The 4 cases presented in this symposium were as follows: an infant with Down syn- drome showing an atypical clinical course of transient abnormal myelopoiesis (TAM) and myeloid leukemia, a relatively older girl with juvenile myelomonocytic leukemia (JMML), one adult with acute myeloid leukemia (AML) with inv (16) (p13.1q22); CBFB-MYH11 morphologically resembling AML with t (8;21) (q22;q22.1); RUNX1-RUNX1T1, and one adult with high-grade B-cell lymphoma showing t (14;18) (q32;q21); IGH/BCL2. Each case included pathological and interesting morphological findings that were carefully examined and in- tensively discussed by two experienced commentators and participants, including pediatric hemato- pathologists. The importance of the morphological evaluation of characteristic cells such as immature leukemic blasts or lymphomatous ones was reconfirmed at this conference. In addition, immunological, cytogenetic, and molecular examinations were also essential for the final diagnosis of these cases. [Review].