- 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.
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