Atypical Lymphoid Proliferations

The Pathologist's Viewpoint

Mahmoud Rezk Abdelwahed Hussein


Expert Rev Hematol. 2013;6(2):139-153. 

In This Article

Scope of the Review

Immune cells of the lymph node form an integrated system whereby a lymphoproliferative response to antigenic stimuli may be elicited. Several antigenic stimuli can eventuate into a series of immunophenotypically and genotypically well-characterized benign (reactive hyperplasia and lymphadenitis) or neoplastic (lymphomas) B-cell or T-cell or natural killer (NK)-cell changes. Some antigenic stimuli may result in lymphoid proliferations that exhibit worrisome cytoarchitectural features but do not fulfill the full criteria for the diagnosis of lymphoma – that is, atypical lymphoid proliferations (AtLP). They show some features associated with lymphoma but lack the full criteria of malignancy. The AtLP are therefore considered as conditions in which it is not possible to differentiate between the benign and the malignant nature of a given lymphoid infiltrate. Use of this designation acknowledges the gray zones in the spectrum of the lymphoid proliferations, and the difficulties in accurately predicting the clinical outcome of some individual lesions. To date, there are no criteria for defining and classifying AtLP. Also, worrisome features that predict whether a patient with AtLP will have a self-limited illness or one that will eventually result in lymphoma or death are not well known. This study was undertaken with a view to introduce the category of AtLP. It discusses the etiology, histogenesis, clinical features of AtLP and their separation from malignant lymphomas. It also presents case series illustrating this category.