ABSTRACT
Primary extranodal lymphoma was first recognized in the mid-20th century. The generally agreed upon definition of primary extranodal lymphoma is disease confined to a single extranodal site, with or without regional lymph node involvement. In 1997, the International Extranodal Lymphoma Study Group was organized and has been active in promoting natural history studies and therapeutic trials. The introduction of positron emission tomography scans in the staging of lymphoma has generated some issues unique to extranodal marginal zone lymphoma of mucosa-associated lymphoid tissue. The new wave of molecular science in lymphoma has identified genetic signatures that correlate with prognosis in large cell lymphoma. About 73% of patients with diffuse large cell lymphoma who show amplification of REL were, in fact, primary extranodal lymphoma. This technology has been applied to primary mediastinal large B-cell lymphoma of presumed thymic origin, which has been shown to share some molecular genetic features with classic Hodgkin’s lymphoma.
