FDG-PET in lymphomas

Lymphomas are a heterogeneous group of neoplasms in which two major subtypes are distinguished, Hodgkin's disease (HD) and non-Hodgkin's lymphomas (NHL). The incidence of lymphomas is about 20 per 100000 inhabitants (Jemal et al 2002) and 7-8 times higher than that of HD. Since NHL has a worse prognosis, the death rates of NHL are 14 times higher than those for HD. Lymphomas account for about 4 % of all cancer incidences. In USA, lymphomas are the fifth most frequent cancer type diagnosed and the third most frequent form of cancer death (Jemal et al 2002). Concerning HD, there is a preponderance for males with a gender ratio of 1.33 for incidence and 1.12 for mortality. For NHL incidences and mortality rates of genders are almost equal. HL comprises different subtypes among which nodular sclerosis is the most frequent one (60-70 %). Other histopathologic subtypes are those of mixed cellularity, lymphocyte reach and lymphocyte depleted characteristics. The most frequent subgroup of NHL are B-cell lymphomas (80-90 % of all NHL). Two thirds of this subgroup are diffuse large B-cell lymphomas, one third follicular lymphomas. Other (less frequent) subtypes are mantle cell, peripheral T-cell, anaplastic large-cell-lymphomas etc. For NHL increasing incidence has been observed in the last decades. Within 15 years the incidence increased by 50 % in the USA (Jemal et al 2002). Etiology of lymphomas is still unknown. In a certain proportion of NHL viral causes are assumed. Diagnosis is based on histology (needle biopsy) with consecutive sub typing. Prognosis depends on stage, expansion state, histology and proliferation rates. (author)