Extranodal lymphomas.

At least one quarter of non-Hodgkin's lymphomas (NHL) arise from tissue other than lymph nodes and even from sites which normally contain no lymphoid tissue. These forms are referred to as primary extranodal lymphomas [1,2]. Since these tumours, numerous when considered together, are widely distributed throughout the body, it is difficult to find adequate series of any given site. Moreover, many historical series were published before the recognition of mucosa-associated lymphoid tissue as the origin of many extranodal lymphomas and in general, classification of primary extranodal lymphomas was similar to that of nodal lymphomas, without consideration that their origin could be different. Hence, the literature lacks uniformity in histopathological classification. The first attempt to eliminate this problem was made only very recently with the proposal of the Revised European-American Lymphoid Neoplasms (REAL) classification [3].