Inflammatory pseudotumor mimicking chronic pulmonary embolism or pulmonary artery sarcoma: Report of five cases

Abstract

Inflammatory pseudotumor (IPT), also known as plasma cell granuloma, is a rare lesion of unknown etiology that occurs in many organs, especially in the lung. Here we report five cases of IPT arising in pulmonary artery mimicking chronic thromboembolic disease, not previously documented in the literature. Those cases were identified at our institute among over 2500 pulmonary endarterectomy (PEA) specimens acquired from 2000 to 2017. The cohort included three men and two women with a median age of 41 years (range: 23-54). All patients presented with dyspnea and radiologic findings of pulmonary artery thromboembolism, some concerning for intimal sarcoma. The duration between disease onset and PEA ranged from 6 months to approximately 3 years. Histologically, all cases showed proliferation of spindle cells with marked inflammatory infiltrates composed predominantly of plasma cells, histiocytes, and small lymphocytes. Ancillary studies were performed in each case and ruled out other possibilities, such as sarcoma, lymphoma, plasmacytoma, IgG4-related disease, and infection. IPT arising in pulmonary artery presenting clinically as acute or chronic thromboembolic disease is very unusual, in which clinical data, radiographic findings, and histopathologic features have to be integrated for reaching the proper diagnosis.

Keywords: ALK‐1; IgG4; chronic thromboembolic pulmonary hypertension; inflammatory pseudotumor; pulmonary embolism; pulmonary endarterectomy.

Figure 1

Radiology characteristics of Case 1. (a) An axial image from a contrast‐enhanced chest computed tomography (CT) shows a complete filling defect in the right main pulmonary artery (arrows). It is atypical for bland pulmonary thromboembolic disease to result in unilateral occlusion of a main pulmonary artery. (b) A coronal maximum intensity projection (MIP) image demonstrates dilated bronchial arteries (arrows) coursing towards the right lung. (c) A frontal chest radiograph shows diminutive right hilar/pulmonary vessels compared to the left. (d) A VQ scan demonstrates the absence of perfusion in the right lung. Likewise, both CT images show diminished blood flow in the right lung

Figure 2

Case 1. Macroscopic examination (a) shows a mass‐forming lesion. H&E (b) reveals prominent plasma cells and lymphohistiocytic infiltrate. The scattered spindle cells are positive for SMA (c), and negative for ALK (d). IgG highlights markedly increased plasma cells (e), with only scattered immunopositivity for IgG4 (f); (b–f) ×200 original magnification. H&E, hematoxylin and eosin; SMA, smooth muscle action

Figure 3

H&E morphology of Case 2 (a), 3 (b), 4 (c), and 5 (d) shows similar histology to that seen in Case 1, except more confluent spindle cells in Case 5 (d); ×200 original magnification. H&E, hematoxylin and eosin