Primary pulmonary lymphoma.

Three distinct entities are now covered by the definition of primary pulmonary clonal lymphoid proliferation. The aim of this review is to describe the pathophysiological, diagnostic, prognostic and therapeutic aspects of these three entities. Low-grade pulmonary B-cell lymphoma is the most frequent form of primary pulmonary clonal lymphoid proliferation. It arises from mucosa-associated lymphoid tissue. It is usually indolent and appears in the form of a chronic alveolar opacity. The prognosis is excellent, but treatment is controversial (simple monitoring, surgery or single-agent chemotherapy). High-grade pulmonary B-cell lymphoma is far rarer and usually occurs in individuals with an underlying disorder (e.g. immunodeficiency). The prognosis is poor and therapeutic options depend on the underlying disorder. The inclusion of lymphomatoid granulomatosis in the definition of primary pulmonary lymphomas is controversial. The clonal nature of the proliferation is very rarely demonstrated and extrapulmonary involvement is frequent (upper airways, skin, kidneys, central nervous system, etc.). The prognosis is extremely variable, with some authors reporting complete remission with steroids and cyclophosphamide and others reporting failure of combination chemotherapy.