Retrospective analysis of dendriform pulmonary ossification: Possible involvement of inflammation and hemorrhage

Abstract BackgroundDendriform pulmonary ossification (DPO) is a rare condition characterized by metaplastic bone formation in the lung parenchyma. DPO has been reported to be often associated with usual interstitial pneumonia (UIP) or chronic aspiration of gastric acid; however, DPO is believed to be a multifactorial disease, and its clinical features and pathophysiology remain unclear. This study aimed to reveal the novel clinical features and pathophysiology of DPO.MethodsThe pathology reports of consecutive cases diagnosed by surgical lung biopsy for diffuse lung diseases (DLDs) between April 1, 2000 and March 31, 2018 were reviewed retrospectively. Cases showing ossification in their specimens were subsequently reviewed and confirmed as calcified density lesions on CT scans. Besides the definite DPO cases, two DPO cases that involved surgical resection of the lung tumor were also included in the study. The clinical, radiological, and pathological features were analyzed.ResultsThree (0.96 %) out of 313 cases with DLDs were identified as cases of definite DPO. Taken together with the two DPO cases showing lung tumors, five DPO cases were analyzed. The patients were predominantly male, with a median age of 69 years. Four cases showed no smoking history. One patient had gastroesophageal reflux disease and UIP, and another had demonstrable hiatal hernia. Laboratory data were not remarkable. Pulmonary function at baseline was almost normal, and no significant decline was observed during the follow-up period. All cases showed interstitial fibrosis accompanied by ossifications. Intriguingly, the histological examination revealed intra-alveolar fibrosis and slight inflammatory cell infiltration, including new bone formation, corresponding to the consolidation on the CT scan in one case. In addition, consolidation, suspected to be caused by inflammation or hemorrhage, was also noted in two other DPO cases, namely in all of three idiopathic cases without UIP or risk factors for gastric acid aspiration.ConclusionsAll five DPO cases were indolent, indicating that the prognosis of DPO might be good. The pathological and radiological findings suggested the possible involvement of pulmonary inflammation and hemorrhage in the pathogenesis of DPO.