Can a specifically-aimed pathologic classification overcome the difficulties in defining HIV-associated lymphomas?

High grade B-cell systemic lymphomas in HIV-infected patients exhibit pleomorphic features as well as some overlap between established histologic subtypes thus highlighting the difficulties in defining them precisely by making use of the classifications for non-Hodgkin's lymphomas (NHL) proposed before the AIDS epidemic. A series of HIV-associated systemic lymphomas including 114 NHL and 25 Hodgkin's disease (HD) cases were morphologically and immunopheno-genotypically investigated at the Centro di Riferimento Oncologico, Aviano, Italy during a period of nine years. The International Working Formulation (WF) for NHL, the updated Kiel Classification and, later, morphologic variants of high grade B-cell NHL have been adopted in order to obtain a more detailed and specific histopathologic description of HIV-associated lymphomas. As a consequence of morphologic data, and considering also pathogenetic aspects as derived from literature, we have attempted a pathological categorization of HIV-associated systemic lymphomas based on the recognition of two main groups: the "blastic" cell group and the "anaplastic" one, both including specific cytomorphologic subtypes with, possibly, aggressive HD subtypes within one of them. This categorization uses the WF, the updated Kiel system, and the morphologic variants of high-grade lymphomas, and provides a provisional category for cases with intermediate morphologic features. Thus other histologic subtypes, such as small noncleaved cell (Burkitt) and immunoblastic lymphomas, can be defined in a more accurate way. The clear-cut placement of "anaplastic" cell lymphomas, including anaplastic large cell (CD30/Ki-1+) lymphomas, including anaplastic large cell (CD30/Ki-1+) lymphomas and possibly a proportion of HD cases, emphasizes the need for their diagnostic differentiation from polymorphic "blastic"' cell lymphomas, immunoblastic ones in particular.