Lymph Node Lesions
Pathological examination of involved tissue occupies an extremely important place in establishing the diagnosis of IgG4-related disease (IgG4-RD). However, the histological picture in IgG4-RD can vary significantly from organ to organ in this disease even
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Lymph Node Lesions Yasuharu Sato and Tadashi Yoshino
27.1
Introductory Remarks
IgG4-RD is often accompanied by lymph node swelling and in some patients lymphadenopathy is the presenting sign [1–3]. Malignant lymphoma and other lymphoproliferative disorders are frequently suspected clinically [2]. Two hallmarks of IgG4-RD in most organs affected by this disease are fibrosclerosis and obliterative phlebitis. In IgG4-related lymphadenopathy, however, these features are almost never noted. Moreover, the histological spectrum of lymph node lesions is extremely wide, precluding an easy diagnosis [1, 2]. Of the pathological diagnostic criteria for IgG4-RD, in addition to IgG4+ cell infiltration, an IgG4+/IgG+ cell ratio >40 % is important diagnostically [2, 4]. Despite this, the lymph node lesions of numerous cases in non-IgG4-RD conditions, such as multicentric Castleman’s disease, rheumatoid lymphadenopathy, and other immune-mediated conditions, easily satisfy these histological diagnostic criteria [5–8]. And since these non-IgG4-RD, like IgG4-RD, show a high frequency of lymph node involvement, their differentiation from IgG4-related lymphadenopathy is always problematic. At least five histological types of IgG4-related lymphadenopathy are thought to exist [1] (Table 27.1). In this section, we outline the pathological tissue findings and essential points in the differential diagnosis of IgG4-related lymphadenopathy.
Y. Sato (*) • T. Yoshino Department of Pathology, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, 2-5-1Shikata-cho, Kita-ku, Okayama 700-8558, Japan e-mail: [email protected]
27.2
Histopathological Characteristics of IgG4-Related Lymphadenopathy
Below we outline the histopathological characteristics and differential diagnosis of each histological subtype of IgG4related lymphadenopathy.
27.2.1 Type I: Multicentric Castleman’s Disease-Like Systemic lymph node swelling develops at an early stage of disease in many cases. One histological feature of the lymph node is interfollicular expansion with normal to hyperplastic germinal centers. The germinal centers are penetrated by blood vessels. Abundant mature plasma cells and scattered eosinophils are apparent in the interfollicular zone. The majority of the infiltrating plasma cells are IgG4positive (Fig. 27.1). These histological features strongly resemble those of multicentric Castleman’s disease (MCD) [1, 2]. Certain important differences between MCD and IgG4-related lymphadenopathy exist: the germinal centers in MCD are often small or atrophic, and eosinophils are not prominent [5]. Differentiation between these two conditions can be challenging, however, because MCD sometimes fulfills the diagnostic criteria for IgG4-RD (i.e., IgG4+/IgG+ cell ratio >40 %) and elevated serum IgG4 levels [5]. For this reason, it is extremely dangerous to base the differential diagnosis of the two diseases solely on the immunostaining results. Rather, a comprehensive diagnosis that also takes into account the results of cl
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