Type and maturational status of dendritic cells in cutaneous B cell lymphoproliferative disorders.

AIMS: B cell cutaneous lymphoid hyperplasia (B-CLH) and cutaneous mucosa-associated lymphoid tissue (MALT) lymphoma represent opposite poles of the same disease spectrum. We explored the hypothesis that dendritic cells (DCs) are central in the generation and regulation of such lesions. METHODS AND RESULTS: Immunohistochemistry was used to identify Langerhan cells (LCs), dermal DCs (DDCs) and plasmacytoid DCs (PDCs), as well as mature and alternatively activated DCs, in B-CLH (n = 14) and cutaneous MALT lymphoma (n = 18). PDCs were most numerous in both types of lesion, but there were significantly more PDCs and DDCs and greater numbers of mature DCs in B-CLH. Nevertheless, DCs were still present in cutaneous MALT lymphoma and there were also proportionately more alternatively activated cells. CONCLUSION: Mature DDCs are prime activators of naive T cells and our results suggest that they are likely to be largely responsible for driving the initial proliferation in B-CLH. The results also suggest that PDCs play a central role, and we hypothesize that they dictate the magnitude, duration and direction of the response. In cutaneous MALT lymphoma PDCs are the dominant DC subtype, and may act by damping down the antitumour host immune response, as well as directly stimulating the growth and differentiation of the neoplastic lymphocytes.

A simple and rapid approach to the problem of tissue contamination and patient identity in histopathologic specimens.

Individual pathologists deal with thousands of diagnostic biopsy and excision specimens annually. At each stage, procedures are in place to limit the possibility of human error, which could result in specimen transposition or contamination. One specimen contaminating another is usually easily identified and rarely causes diagnostic difficulty; however, when it does, the consequences can be very serious. We discuss 5 cases in which concerns over specimen identity and tissue contamination arose and the methodology by which we resolved those concerns. Polymerase chain reaction analysis of each case was carried out using a panel of 12 polymorphic microsatellite markers, specific for chromosomes 13, 18, and 21. These markers are routinely used in the molecular genetics diagnostic laboratory for rapid trisomy screening. In each case, the question of error was satisfactorily resolved. Using this approach, we prevented the real possibility of patients undergoing second invasive procedures. We suggest that this or a similar methodology become a routine part of pathology practice.

Lesions resembling Langerhans cell histiocytosis in association with other lymphoproliferative disorders: a reactive or neoplastic phenomenon?

Langerhans cell histiocytosis (LCH) has been described in association with a variety of neoplasms preceding, after, or synchronous with the other tumor. In some cases, a neoplasm may arise as a complication of therapy for LCH, and in others, the association may be coincidental. Synchronous occurrence has been reported most commonly in association with malignant lymphoma in which discrete proliferations of Langerhans cells (LCs) histologically indistinguishable from LCH are seen. In most cases, these LCs are closely related to or intermingling with the primary pathology. The nature of LCs in this context remains elusive with debate as to whether they represent a true clonal neoplasm or an exaggerated reactive phenomenon. The lack of evidence for LCH progression or disease elsewhere strongly supports the latter. We have encountered 5 examples of LCH-like proliferations occurring in the context of other lymphoproliferative disorders. These include 2 cases of mycosis fungoides and 1 of cutaneous B-cell pseudolymphoma, associations that to our knowledge have not been described before. Two patients were female, and the clonality of the LC proliferation was assessed using laser capture microdissection and the human androgen receptor. The results showed that the LCs forming discrete nodules in a case of cutaneous B-cell pseudolymphoma and a case of Hodgkin's lymphoma were polyclonal. This suggests that, at least in a proportion of cases, the aggregates of LCs occasionally identified within other lymphoproliferative lesions represent a reactive proliferation rather than a potentially aggressive second neoplasm.