Inflammatory pseudotumor (IPT) of lymph node is a histiocytic and fibroblastic non-neoplastic proliferation involving the lymph node connective tissue framework and associated with vascular lesions.

An exaggerated inflammatory proliferative process may cause tumor-like enlarged lymph nodes in patients with nonspecific constitutional symptoms (1,2,3,4,5,6). The main components of the cellular proliferation are histiocytes and fibroblasts of the lymph node framework, although marked vascularity and infiltration of various inflammatory cells are also part of the process. As a result, tumor-like growths develop with spindle cell histologic patterns similar to those of the pseudotumors and “plasma cell granulomas” described in the lung (7), liver (8), spleen (9,10,11,12), mesentery and intestine (13,14), pancreas (15), urinary bladder (16), orbit (17), and skin (18). Extranodal IPT has rarely been associated with regional lymph node involvement (14). The etiology and pathogenesis of ITP are unclear. Some, but not all, have been associated with acute episodes of fever and night sweats, suggesting an infectious origin. Cases of ITP with a simultaneous onset of rheumatoid arthritis (19) as well as associated with inflammatory lesions of the mesentery (20) or retroperitoneum (21) have been reported. Epstein-Barr virus (EBV) is found in the spindle cells of one-half to two-thirds of extranodal IPTs, but in the mononuclear cells of only a few nodal IPTs (22). It is not likely that EBV is involved in the pathogenesis of IPT in lymph node, but it may have a role in spleen and liver (23).

In the lymph node, the proliferating histiocytes and fibroblasts are located primarily in the hilum, trabeculae, and capsule, where they expand toward the lymphoid parenchyma. The cause of this exuberant cellular proliferation, which in many ways resembles nodular fasciitis, another idiopathic IPT process, is unknown. It is believed that local release of cytokines, possibly interleukin 1, an active promoter of cell activation and inflammatory reaction, may be involved in the origin of this unusual exaggerated pseudotumoral response to infection or injury (1,2). Inflammatory pseudotumor of lymph nodes is a rare occurrence, non-neoplastic, with a chronic course and usually spontaneous remission (1,2,3,4). Its major importance resides in its potential misdiagnosis as a real malignant condition.

In the few series of cases reported, the age range was broad (7 to 82 years, with a median of 33 years), and no gender predilection was noted (1,2,3,4). Variable episodes of fever, night sweats, anemia, hypergammaglobulinemia, and enlargement of lymph nodes, localized or generalized, lasted several weeks to several years (1,2,3,4). Mandibular, cervical, axillary, mediastinal, retroperitoneal, and inguinal lymph nodes and the perinodal soft tissues were involved. Resolution occurred after various treatments, including antibiotics, chemotherapy, radiotherapy, and after no therapy (1,2,3,4). The removed lymph nodes were as large as 3 cm in diameter, hard, matted together, and adherent to adjacent structures, and their cut surfaces had a “fish flesh” appearance (1).