Fact-sheet: Inflammatory pseudotumor of the lung
Updated on 04/23/2018 at 9:21 AM
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Definition
- Rare benign lung tumor (0.7 to 1% of bronchopulmonary tumors)
- Predominantly pulmonary parenchymal, rarely endobronchial in children
- Initially described in 1921 by Symmers as an unusual form of malignant lung tumor
- Presenting as a solitary nodule, mimicking a malignant tumor.
- Unknown etiology (immunologic response to an infectious or non-infectious agent according to some authors)
- More than half of cases occur before age 40, and 15% between 1 and 10 years of age
Clinical features
- Asymptomatic lesion in 50% of cases
- Otherwise:
- cough
- hemoptysis
- dyspnea
- chest pain
- cyanosis
- digital clubbing
- In 15 to 30% of cases, systemic signs (fever, growth retardation, weight loss)
Radiography
- round, well-circumscribed solitary nodule
- intraparenchymal
- mean size of 4 cm
CT
- mass with regular margins
- occasionally cavitated
- calcifications in 25% of cases
- assessment for local invasion and extrapulmonary involvement
Nuclear medicine
- PET/CT: hypermetabolism related to inflammatory changes
Management
- Surgical treatment (segmentectomy, lobectomy, or pneumonectomy)
- Oncologic resection justified by the angioinvasion sometimes described, the possible microscopic invasion of adjacent tissue, and the potentially malignant nature of these tumors.
- Some cases of spontaneous regression after biopsy have been reported in the literature
Classification
- Coffin WHO histologic classification
- Type 1: "myxoid vascular" (myofibroblasts within a granular tissue)
- Type 2: "compact spindle" (cellular proliferation with variable myxoid and collagenous regions)
- Type 3: "hypocellular fibrous" (scar-like appearance with rare inflammatory cells)
- Matsubara histologic classification:
- Type I "organizing pneumonia" (44%) featuring intra-alveolar inflammation progressing to peripheral alveolar fibrosis and central interstitial fibrosis.
- Type II "fibrohistiocytic" (44%) corresponds to an intense proliferation of spindle cells and histiocytes.
- Type III "lymphoplasmacytic" (12%) predominance of lymphocytes and plasma cells with little fibrosis.
