Recognizing but not harming. Borderline B‐cell lymphoid proliferations

Abstract

AbstractIn the last years several borderline B‐cell lymphoid proliferations have been recognized that lie at the interface between benign and malignant. These lesions can be divided in two groups; those considered precursor lesions of well recognized lymphoid malignancies and the group of indolent lymphomas with limited potential for progression. Precursor lesions are monoclonal and share many genetic features of their malignant counterpart. The first recognized precursor lesion was monoclonal gammopathy of undetermined significance. Thereafter, the widespread use of immunohistochemistry, fluorescence‐activated cell sorting analysis and molecular techniques in lymphoid samples led to the recognition of other precursor lesions such as monoclonal B‐cell lymphocytosis, in situ follicular neoplasia and in situ mantle cell neoplasia. The second group of disorders comprises monoclonal lymphoid proliferations with limited malignant potential without a counterpart among the currently recognized lymphoma entities; these include pediatric‐type follicular lymphoma, pediatric nodal marginal zone lymphoma, and duodenal‐type follicular lymphoma. Despite their clonal nature, a conservative treatment has been shown to be sufficient in most cases. The diagnostic criteria of precursor/indolent B‐cell proliferations, recent advances in the understanding of progression and lymphomagenesis and current recommendations for treatment will be discussed. In order to avoid unnecessary and potentially harmful therapy, these lesions need to be recognized and diagnosed correctly.