대한흉부영상의학회 Korean Society of Thoracic Radiology

Discussion

Diagnosis With Brief Discussion

Diagnosis

Inflammatory Pseudotumor

Radiologic Findings

Chest PA shows an about 2-cm-sized well-defined round nodule in right lower lung zone.

On CT scan, the lesion is located just posterior to the right major fissure and shows slightly lobulated margin anteriorly.

On enhanced scan, the attenuation value of the nodule is similar to that of chest wall muscle.

On pathology (below), the nodule was composed of fibroblasts, collagen and inflammatory cells, mainly of lymphocyte and plasma cells.

Brief Review

Pulmonary inflammatory pseudotumor is an uncommon, non-neoplastic, occasionally aggressive proliferative process that may begin as an organizing pneumonia.

It has many synonyms, including plasma cell granuloma, inflammatory myofibroblastic tumor, histiocytoma, xanthoma, fibroxanthoma, xanthogranuloma, plasma cell tumor, fibrous xanthoma, xanthomatous pseudotumor, and plasma cell-histiocytoma complex.
And the term inflammatory pseudotumor has been widely accepted.

Gross pathology demonstrates that pulmonary inflammatory pseudotumors are typically well-defined, firm, lobulated parenchymal nodule or mass with a whorled and often heterogeneous appearance on cut section.

The histologic findings are proliferation of spindle-shaped fibroblasts and permeation of collagen with lymphocytes, fibrosis, granulomatous inflammation, lymphoid hyperplasia, and intraalveolar fibrosis at the edge of the tumor.

Pulmonary inflammatory pseudotumor is typically a solitary, peripheral, sharply circumscribed, lobulated mass with an anatomic bias for the lower lobes.

CT most commonly shows a well-marginated, lobulated mass of heterogeneous attenuation with variable patterns of contrast enhancement and calcification.

T1-weighted MR images typically show a heterogeneous mass of intermediate signal intensity that displays a nonspecific increase in signal intensity on T2-weighted images.

Extraparenchymal extension and primary involvement of mediastinal and hilar structures are unusual.

Calcification within the lesion is uncommon, but not rare.

The tumor occurs more frequently in children than in adults.

Atelectasis and pleural effusion may occur.

Cavitation and lymphadenopathy are rare.

The radiologic differential diagnosis for pulmonary inflammatory pseudotumor is extensive because the typical lesion may be characterized as a solitary pulmonary nodule or mass.

A primary or metastatic neoplasm should be considered, but in children without an underlying malignancy, a solitary peripheral pulmonary nodule or mass is more likely to represent an inflammatory pseudotumor than a neoplasm.

References

1. Agrons GA, Rosado-de-Christenson ML, Kirejczyk WM, et al. Pulmonary inflammatory pseudotumor : radiologic features. Radiology 1998;206:511-518

2. Kim HS, Jung GS, Baek KH, et al. Inflammatory pseudotumor of the lung : CT findings and pathologic correlation. J Korean Radiol Soc 1998;38:75-82

3. Shapiro MP, Gale E, CarterBL. Variable CT appearance of plasma cell granuloma of the lung. J Comput Assist Tomogr 1987;11(1):49-51

Keywords

Lung, Benign tumor,