[Lymphomatoid granulomatosis]

Lymphomatoid granulomatosis, described in 1972 by Liebow, is a rare, Epstein-Barr virus (EBV)-associated lymphoproliferative disorder, involving the lung, and often the skin or the central nervous system. It could have a systemic course making its diagnosis difficult. Controversy still remains about precise taxonomy and lymphomatoid granulomatosis is classified as a lymphoma, whose severity extends from indolent forms to aggressive large B cell lymphomas. Histology is essential and shows characteristically an inflammatory angiocentric infiltrate, composed with polymorphous mononucleated cells containing a varying number of large atypical CD20-positive B-lymphocytes within a background of numerous small reactive CD3-positive T-lymphocytes, often associated with necrosis. In situ hybridization often shows EBV RNA within atypical B-cells. Atypical large B-lymphocytes proportion and to a lesser degree EBV-positive B-lymphocytes proportion allow to classify the disease (grade I to III) and have a prognostic value. An aggressive form of B lymphoma occurs in 7 to 47% of cases during lymphomatoid granulomatosis course. Moreover, grade III diseases share numerous characteristics of lymphoma and often require chemotherapy. Several conditions mimic lymphomatoid granulomatosis, and include various hematologic malignancies (large B-cells lymphomas, T/NK lymphomas, post-immunodepression lymphoproliferative disorders) or granulomatosis with polyangiitis. The objective of this article is to review the clinical, radiological, histological and therapeutic characteristics of this rare disorder.