Epidemiology
Hodgkin’s lymphoma is an uncommon cancer and over the past 50 years advances in radiotherapy and the introduction of combination chemotherapy have tripled the cure rate. Now more than 80% of newly diagnosed patients can expect a disease-free normal lifespan.
More men than women present with Hodgkin’s lymphoma and the age-specific incidence of the disease is bimodal, with the greatest peak in the third and seventh decades. The age-specific incidence of Hodgkin’s lymphoma differs markedly in different countries. In Japan, the overall incidence is low and the early peak is absent. In some developing countries, there is a downward shift of the first peak into childhood.
Aetiology
The cause of Hodgkin’s lymphoma remains unknown, and there are no well-defined risk factors for its development. However, certain associations have been noted that provide clues to possible aetiological factors. Same-sex siblings of patients with Hodgkin’s lymphoma have a 10-fold higher risk for the disease and a monozygotic twin sibling of a patient with Hodgkin’s lymphoma has a 99-fold higher risk of developing the disease than a dizygotic twin.
Familial aggregation may imply genetic factors, but other epidemiologic findings mentioned above suggest an abnormal response to an infective agent. The Epstein–Barr virus (EBV) has been implicated by both epidemiological and serological studies in addition to demonstrating the EBV genome in 20–80% of Reed–Sternberg cells. In patients with HIV infection there is a sixfold increase in Hodgkin’s lymphoma.
Pathophysiology
Nodular sclerosing (60%) is the most common subtype, typically seen in young adults (more common in females) who have early-stage supradiaphragmatic presentations. It is composed of large tumour nodules, with scattered lacunar classical Reed–Sternberg cells set in a background of reactive lymphocytes, eosinophils and plasma cells with varying degrees of collagen fibrosis/sclerosis. These patients have a good prognosis.
Mixed cellularity (30%) is the second most common histology. It is more common in males, who present with generalised lymphadenopathy or extranodal disease and with associated B symptoms. Reed–Sternberg cells are frequently seen but bands of collagen are absent, although a fine reticular fibrosis may be present. The cellular background includes lymphocytes, eosinophils, neutrophils and histiocytes.
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