Granulomatous Lymphadenitis

Shigeyuki Asano

In this review, representative types of granulomatous lymphadenitis (GLA) are described. GLA can be classified as noninfectious GLA and infectious GLA. Noninfectious GLA includes sarcoidosis and sarcoid-like reaction. The cause of sarcoidosis remains unknown, but it has good prognosis. Sarcoid-like reaction, which is considered to be a biological defense mechanism, is observed in regional lymph nodes with many underlying diseases. Infectious GLA can be classified as suppurative lymphadenitis (LA) and nonsuppurative LA. Suppurative LA generally shows follicular hyperplasia and sinus histiocytosis in the early phase. In tularemia and cat scratch disease, monocytoid B lymphocytes (MBLs) with T cells and macrophages contribute to the formation of granuloma. However, none of the epithelioid cell granulomas of Yersinia LA contains MBLs like in cat scratch disease. In addition, almost all have a central abscess in granulomas induced by Gram-negative bacteria. In terms of the lymph nodes, tularemia and cat scratch disease are apt to affect the axillary and cervical regions while Yersinia LA affects the mesenteric lymph node. Nonsuppurative LA includes tuberculosis and BCG-histiocytosis. These are induced by delayed allergic reaction of M. tuberculosis. Tuberculosis LA mainly appears in the cervical lymph node. Organisms are histologically detected by Ziehl-Neelsen staining in the necrotic area. Toxoplasmosis is also a nonsuppurative protozoan infection (Toxoplasma gondii). In toxoplasma LA, MBLs can also be seen, but round and organized, well-formed granulomas are not found in this disease. Furthermore, necrosis is not induced and there are no accompanying neutrophils, eosinophils and fibrosis. GLA described above is associated with characteristic histological findings. An accurate pathological diagnosis using the above findings can lead to precise treatment.