Pulmonary inflammatory pseudotumours (PIP) are solid, non-neoplastic masses which can mimic pulmonary malignancy. They should not be confused with pulmonary pseudotumours which usually refer to loculated collections of pleural fluid mimicking a pulmonary mass on chest radiography.
Thought to occur from an uncontrolled response to lung tissue injury. Lesions are typically solitary with a lower lobe predilection.
Pathologically, pulmonary inflammatory pseudotumours are typically well-defined, firm, lobulated parenchymal nodules or masses with a whorled and often heterogeneous appearance on cross-section.
Histologically, there is proliferation of spindle-shaped fibroblasts and permeation of collagen with lymphocytes, fibrosis, granulomatous inflammation, lymphoid hyperplasia, and intra-alveolar fibrosis at the edge of the lesion.
Features on chest radiographs can vary but frequently mimics a solitary, well circumscribed, peripheral lung mass with calcifications in situ. May have an anatomical 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. Cavitation and lymphadenopathy are rare.
Treatment and prognosis
- some authors advocate resection 4
The differential can be quite wide, specific considerations include
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