Atypical lymphoproliferative, histiocytic, and dendritic cell disorders

Abstract

Introduction Atypical lymphoproliferative, histiocytic, and dendritic cell disorders often mimic their more common benign or malignant counterparts, and thus can easily be misdiagnosed. Although it may be challenging to identify these unusual disease entities precisely, doing so may significantly alter further evaluation, prognosis, and management of the patient. Multidisciplinary collaboration between clinicians and pathologists is often required to arrive at a definitive diagnosis. Critical to this process is obtaining adequate tissue, ideally through excisional lymph node biopsy. Although core-needle biopsy may sometimes yield a diagnosis, for many of these entities it will be inadequate. Fine needle aspiration has been demonstrated to be of little value in the diagnosis of lymphoproliferative disorders, as it does not provide an adequate assessment of tissue architecture. In cases where a biopsy is equivocal, additional biopsies may be necessary to establish a firm diagnosis. In this chapter, we will summarize the pathophysiology, presentation, diagnosis, prognosis, and treatment of atypical lymphoproliferative, histiocytic, and dendritic cell disorders. Three main categories of these disorders have been defined (Table 17.1). Benign conditions, such as Kikuchi's disease, often behave indolently and can usually be managed with observation. Histiocytic disorders exhibit a wide range of behavior, and may require more aggressive therapies. Atypical lymphoproliferative disorders can be polyclonal, such as Castleman'sdisease, or malignant, such as lymphomatoid granulomatosis, and are treated in a variety of different ways.