Lymphomas are malignant tumors deriving from the proliferation of cells setting up the immune system. As these cells normally circulate with the blood in the whole organism, lymphomas are generalized tumors from their appearance. However, exceptions do exist leading the Authors of the European Organization for Research and Treatment of Cancer (EORTC) to say that morphologically identical lymphomas, when arising in different organs, are clonal proliferations of distinct lymphocyte subpopulations, which are in some way related to the organ where the lymphoma arose (45).
Lymphomas are much less frequent in children as compared with adults. However, some Authors (5) established that 1/6,000 children under the age of 15 develops lymphoma. According to these Authors, the frequency of lymphomas follows only that of leukemias and brain tumors. (...)