Written by epgonline.org - Last updated 02 May 2018
Non-Hodgkin lymphoma (NHL) comprises a heterogenous group of lymphoid tissue tumours, distinguished from Hodgkin’s lymphoma by their absence of Reed-Sternberg cells on histology. The classification of NHL is constantly evolving, and as new biomarkers and mutations are pinpointed our understanding of the disease progresses and changes.
Collectively, NHL is the most common haematological malignancy, making up 2.7% of cancer cases worldwide, and causing 2.4% of cancer-related deaths. Figures for 2012 put the worldwide annual incidence at 386,000, making it the tenth most common cancer. The incidence increases with age, although there is variation among subtypes.
There are several ways in which NHL as a clinical entity can be broken down: the cell-line of origin is a frequent starting point, with the majority derived from B-cell lines; subtypes are also frequently used, and give a much better indication of prognosis. Diffuse large B-cell lymphoma (DLBCL) is the most common subtype, representing 37% of NHL, with follicular lymphoma accounting for a further 29%; whether the disease is identified as indolent or aggressive also enables differentiation. Numerous genetic mutations that precipitate NHL have been identified, with other potential causative mechanisms also noted – links have been found with immunodeficiency, some infections and environmental causes (including hair dyes and pesticides), while the mucosa-associated lymphatic tissue (MALT) subtype has been associated with chronic inflammation in autoimmune disorders.
The clinical presentation is variable, depending on the subtype, the growth-rate and the location, however the most frequent presenting complaint is with persistent lymphadenopathy. Other common presenting symptoms include splenomegaly, fatigue and shortness of breath, while systemic ‘B’ symptoms (named from the Ann Arbor staging system
) such as fever, night-sweats and weight-loss are also associated with lymphoma.
The gold standard diagnostic test is through histological and immunochemical examination of an excised tissue sample, although biopsy can be used if this is not practical. Depending on the site of the tumour, various imaging modalities can also be used as an aid to diagnosis and staging. Bone marrow biopsy is an important staging tool, while a spectrum of blood tests can also be essential in diagnosis and staging.
Numerous factors have been identified which significantly affect prognosis, including age, serum LDH, baseline haemoglobin, the presence of extranodal disease, and the number of involved sites. Based on known prognostic factors, the International Prognostic Index (IPI) was created in 1993. Since then, several adapted versions have been developed including specific indices for follicular lymphoma and DLBCL although it remains in frequent use.
Follicular lymphoma is generally regarded as incurable, and treatment options reflect this – depending on the tumour and patient characteristics, watch and wait, rituximab and radiotherapy may be tried, while immunochemotherapy with several chemotherapy agents is also an option. By contrast, DLBCL is a curable disease in some circumstances, so more aggressive initial treatment with a combination of all of the above options is more usual.