PMC8387082_01
Abdominal CT axial plane: A - Initial examination on admission. Note large mass involving the abdominal aorta; B - CT scan performed 7 months after the first examination and under treatment with corticosteroid. Note the expressive reduction of the periaortic mass.
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Abdominal computed tomography (CT) showed a large, contrast-enhanced mass (10 x 8 x 4cm) involving the abdominal infrarenal aorta and the iliac arteries and compressing the inferior vena cava with dilated iliac veins and the left ureter (Figure 1A), raising the hypothesis of the lymphoproliferative disease. Five months after initiation of corticotherapy, a new abdominal CT scan was done (Figure 1B), and the initial contrast-enhanced mass had almost disappeared, but it showed an inferior vena cava thrombosis extending to bilateral external iliac veins.
Photomicrographs of the biopsy: A - Fibro conjunctive tissue exhibiting fibrosis, with thick collagen bundles and moderate inflammatory infiltrate with lymphoid aggregates (HE - 40X); B - Obliterating phlebitis (HE - 200X); C - Fibro conjunctive stroma showing thick collagen bundles with few eosinophils, histiocytes and small lymphocytes mixed with plasma cells (HE - 400X); D - Numerous plasma cells surrounding a lymphoid aggregate (HE - 400X).
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This biopsy showed a fibro-connective tissue exhibiting fibrosis, obliterating phlebitis, and moderate mixed inflammatory infiltrates with few eosinophils, histocytes, and small lymphocytes and frequent plasma cells (Figures 2  and 3).
Photomicrographs of the Immunohistochemical staining of the biopsy: A - Numerous IgG positive plasma cells near a lymphoid aggregate (400X); B - Increased number of IgG4 positive plasma cells presenting an elevated IgG4/IgG ratio greater than 30% in areas of more density (400X).
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This biopsy showed a fibro-connective tissue exhibiting fibrosis, obliterating phlebitis, and moderate mixed inflammatory infiltrates with few eosinophils, histocytes, and small lymphocytes and frequent plasma cells (Figures 2  and 3).