A definitive diagnosis of PPFE is made when a high-resolution computed tomography scan discloses the presence of upper lobe pleural thickening and subpleural fibrosis associated with less marked or absent lower lobe involvement.
It must be emphasized that a conclusive diagnosis of PPFE requires a multidisciplinary approach with input involving the clinician, radiologist, and pathologist.
In addition to the above pathologies, other pathologies that can be associated with PPFE may be present.
This feature is not characteristic of PPFE, because in PPFE there is a homogenous intra-alveolar fibrosis with generally preserved alveolar structure and even thickening of the alveolar structures through the process of elastic fiber deposition.
Moreover, an interstitial process (be it inflammation or fibrosis or both) is characteristic of NSIP, whereas in PPFE the process involves elastin deposition in relation to the alveolar walls, with intervening collagen deposition.
Nonetheless, a confident diagnosis of PPFE should only be made in the absence of a relevant occupational exposure history to asbestos as well as the lack of significant numbers of asbestos bodies and sarcoid-type granulomas on histology of a surgical lung excision biopsy sample.
The apical caps representing a localized area of subpleural fibrosis occurring predominantly at the apices of the upper lobes can mimic PPFE (Figure 6).
In the event that there is progression to chronic fibrosis, (3) the chronic fibrosis phase of organizing pneumonia may simulate PPFE by virtue of incorporation of the alveolar myofibroblastic proliferation into alveolar septa and irregular interstitial fibrosis.
Although PPFE is thought to be a rare disease, recent studies reveal that the entity may not be as rare as once thought.
Significantly, Rosenbaum et al (7) attribute PPFE as being an underrecognized or underreported entity rather than being rare.