Angioimmunoblastic lymphadenopathy and related disorders: a retrospective look in search of definitions.

The recent report of an immunoblastic lymphadenopathy (IBL)-like T cell lymphoma has rekindled questions about the nature, reactive or neoplastic, of IBL, angioimmunoblastic lymphadenopathy (AIL), and lymphogranulomatosis X (LgX) and blurred the criteria for their diagnosis. We looked in the literature and our own data for a categorization of AIL (IBL, LgX) and related disorders, needed for future prospective studies. Specific differences in the original histologic definitions and discordant immunophenotypic data may warrant the separate consideration of AIL, IBL and LgX and their subdivision into predominantly T cell or B cell lesions. DNA hybridization and cytogenetic studies of the processes sharing histologic features of AIL (IBL, LgX) demonstrate a continuum of disorders from purely reactive to frankly malignant, which may be categorized as follows: (1) those without evidence of clonality by any of three parameters (immunophenotypic, immunogenotypic, and cytogenetic), for which only the term AIL (IBL, LgX) might be reserved; (2) those with evidence of clonality by all parameters, or AIL (IBL, LgX)-like lymphomas; and (3) those that, due to any discordance among the three parameters, do not fit into either of the above categories, and for which the term AIL (IBL, LgX)-like dysplasias is proposed. This intermediate group seems to be composed of unstable lymphoproliferative conditions, in which a predominant component of normal cells coexists with clonal population(s) that may either disappear with time or selectively proliferate and develop into frank lymphoma.