The MTC originates from parafollicular cells (C cells) within the thyroid and is derived from the neural crest; therefore, it is considered a neuroendocrine tumor.[3,4] Chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL) is characterized by the clonal proliferation and accumulation of mature B cells, typically CD5-positive, in the blood, bone marrow, lymph nodes, and spleen. This evidence concerns the gene CD5 and B-cell chronic lymphocytic leukemia.