Histologically Proven Dendriform Pulmonary Ossification: A Five-case Series

Abstract

Dendriform pulmonary ossification (DPO) is a rare condition characterized by metaplastic bone formation in the lung parenchyma. It has been reported to be often associated with primary lung diseases, such as usual interstitial pneumonia (UIP) or chronic aspiration of gastric acid; however, its clinical features and pathophysiology remain unclear, especially in idiopathic cases. We herein report five DPO cases, including three with an idiopathic origin. In all cases of idiopathic DPO, the pathological and radiological examinations showed localized pulmonary lesions suggesting inflammation or hemorrhaging.

Keywords: dendriform pulmonary ossification; fibrosis; hemorrhaging; inflammation; surgical lung biopsy; usual interstitial pneumonia.

Figure 1.

Flowchart of the study. DPO: dendriform pulmonary ossification

Figure 2.

CT or HRCT images at the time of the diagnosis and histopathological findings of the surgical lung biopsy. (Case 1) Hematoxylin and Eosin (H&E) staining, ×40. (Cases 2-4) H&E staining, ×20. (Case 5) Elastica van Gieson stain, ×20. Arrows indicate calcified dense lesions. HRCT: high-resolution computed tomography

Figure 3.

Chest CT images and histopathology of surgical lung biopsy specimens in Case 1. (A, B) Pulmonary window and mediastinal window settings of chest CT at the first visit showed diffuse reticulonodular shadows in both lower lobes (arrows) and a 3-cm nodular shadow in the right lower lobe (arrowhead). (C, D) Chest CT at 13 days before surgery showed consolidation (arrow) next to a 3-cm nodular shadow (arrowhead) in the right lower lobe, which included calcified densities. (E) The specimen obtained by a surgical lung biopsy revealed the presence of several irregularly shaped segments of interstitial bone, some of which contained fat marrow tissues (arrow) [Hematoxylin and Eosin (H&E) staining, ×40]. (F) Ossifications (inset) surrounded by osteoblasts (arrowheads) with intra-alveolar fibrosis and slight inflammatory cell infiltration (arrows), corresponding to consolidation in the right lower lobe (H&E staining, ×10), were observed.

Figure 4.

Chest CT images in Case 2. (A, B) High-resolution CT showed consolidation including calcified density in the right upper lobe (arrow). (C, D) The consolidation had regressed spontaneously after two months.

Figure 5.

Chest CT images in Case 3. (A, B) High-resolution CT showed a round, 3-cm nodule in the right lower lobe (arrow). (C, D) The nodule had regressed spontaneously after seven weeks.