Inflammatory pseudotumor of the thymus: A case report and review of the literature

Abstract

Inflammatory pseudotumors are rare benign tumors consisting of cellular and stromal elements of a localized reactive process. While inflammatory pseudotumors are commonly detected in the lung and occasionally in other organs, only one case of inflammatory pseudotumor of the thymus has been reported in the literature to date. This report presents a 54-year-old male patient with inflammatory pseudotumor of the thymus accompanied by pulmonary inflammation. The patient presented with chest pain and moderate fever for 12 days. Enhanced computed tomography of the thorax revealed an anterior mediastinal solid and cystic mass, which constricted the left brachiocephalic vein accompanied by bilateral lung inflammation and marginal pleural effusion. The patient underwent a median sternotomy for the surgical removal of the mass. Histologically, the resected mass was composed of necrotic and fibrous tissues and inflammatory infiltrates, and the diagnosis was confirmed as an inflammatory pseudotumor of the thymus. The patient's symptoms were resolved following surgery and the patient remained asymptomatic during the six-month follow-up period. In addition, we reviewed the previous literature and discussed the diagnosis and management of our patient. This report provides further insights into the pathogenesis and underlying mechanisms of inflammatory pseudotumors of the thymus to aid in the diagnosis and development of effective therapies.

Keywords: case report; inflammatory pseudotumor; literature review; thymus.

Figure 1

Enhanced computed tomography shows an anterior mediastinal mass (8.3×6×3.5 cm) with heterogeneous contrast enhancement, with an unclear plane separating it from (A) the constricted left innominate vein (white arrow) and (B and C) the aorta and the superior vena cava, and with (D) a trace of pleural effusion (white arrow).

Figure 2

Histological analysis of the mass. The mass (8.3×6.0×3.5 cm) was surgically removed from the mediastinal pleura and subjected to histological and immunohistochemical analyses. Briefly, tissue sections were stained with H&E or anti-CD68, -CD21, -MUM-1, -S-100, -CK or-CD1a overnight at 4°C. The control sections were treated with the same isotype IgG or sera from healthy animals. Subsequently, the bound antibodies were detected with horseradish peroxidase-conjugated secondary antibodies and visualized with 3,3′-diaminobenzidine. (A) Photograph of the gross mass; (B) H&E staining of the tissue section (magnification, ×200: scale bar, 50 μm). (C) Immunohistochemical analysis of CD68, CD21, MUM-1, S-100 and CK (magnification, ×100; scale bar, 20 μm), and CD1a (magnification, ×200; scale bar, 50 μm). Data are representative images and the control sections show no specific staining (data not shown). H&E, hematoxylin and eosin; CD, cluster of differentiation; MUM, multiple myeloma oncogene; CK, cytokeratin.