Cicatricial organizing pneumonia: a clinicopathologic and radiologic study on a cohort diagnosed by surgical lung biopsy at a single institution.

Cicatricial organizing pneumonia (CiOP) refers to intraluminal collagen deposition in a background of otherwise classic appearing organizing pneumonia (OP), sometimes with formation of peculiar fibrous nodules or densely fibrotic linear bands. Dendriform ossification has been also described in CiOP cases. This study is to evaluate the clinicopathologic and radiologic characteristics of CiOP identified in a cohort of OP cases diagnosed by surgical lung biopsy at a single institution. Electronic search was performed to find surgical lung biopsy cases with OP as the main histopathologic diagnosis during a 9-year period (2005-2013). The presence of mature collagen deposition in intraluminal plugs of OP (Masson bodies), linear fibrous bands, and ossification in association with OP was evaluated. Pertinent clinical information was obtained from medical records, and available chest computed tomography (CT) scans were reviewed by a chest radiologist. A total of 56 cases met the study criteria. Thirty-two of 56 cases (57.1%) showed at least 10% of cicatricial element within Masson bodies, 9 of which revealed cicatricial elements comprising 50% or higher proportion of OP. All 9 cases with CiOP as the major component (≥50%) revealed some areas of linear fibrous bands. Five of these 9 cases had intraluminal ossification, with features suggestive of dendriform ossification. Twenty of 32 cases with the cicatricial component had postoperative follow-up CT scans ranging from 0.4 to 171 months (median = 44) after the biopsy; 18 of these 20 cases showed stable finding or resolution of radiologic densities. Six of 9 patients with CiOP with major cicatricial change (≥50%) were alive and well at the time of clinical follow-up (median = 47 months; range = 12-125). In summary, minor cicatricial changes involving Masson bodies were seen in more than half of our OP cases, and patients with CiOP seem to follow an indolent and favorable course on radiologic and clinical follow-up, even in those with major cicatricial changes (≥50%) that were often accompanied by linear fibrous bands and/or intraluminal ossification.