Selected Case From the Arkadi M. Rywlin International Pathology Slide Series

Abstract

Two cases of diffuse dendriform pulmonary ossification (DPO) are presented, one of the secondary type and the other of the idiopathic type. Case 1 was an adult female patient who underwent thoracic surgery to remove a posterior mediastinal bronchogenic cyst, which was discovered on a computed tomography scan performed after an episode of pneumonia when traction bronchiectasis with interstitial lung disease/fibrosis was also suspected in the lungs. Histologic examination performed on the resected lung tissue revealed numerous scattered small osseous spicules on a background of intense interstitial inflammation and fibrosis, leading to further clinical and laboratory investigations and the final diagnosis of DPO secondary to lung involvement by scleroderma. Case 2 was an adult male patient who underwent thoracoscopic exploration after a computed tomography scan, which revealed traction bronchiectasis with linear thickening of the interstitial lung tissue. Histologic examination of the lung tissue specimen revealed numerous osseous spicules in the absence of interstitial septal inflammation. Noteworthy in this case were also some nodules of collagenized tissue similar to those seen in the lungs of patients affected by Ehlers-Danlos syndrome. The absence of any clinical sign or symptoms related to Ehlers-Danlos syndrome attest to the nonspecificity of these pulmonary fibrous nodules. No case of DPO secondary to scleroderma has been reported in the literature so far, although around half of the patients with scleroderma manifest pulmonary diseases. Idiopathic DPO is even rarer, usually discovered postmortem, with only 20 cases diagnosed in life with lung biopsies taken by open surgery or through a thoracoscopic approach. DPO is often misdiagnosed radiologically as bronchiectasis and/or interstitial lung disease/fibrosis.

A Case of Massive Dendriform Ossification Showing Diffuse Interstitial Lung Disease in a Patient With a History of Intensive Occupational Dust Exposure

“…Its manifestations are histologically classified as either nodular or dendriform types; however, the overlap is also common. 1 The exact mechanism of action is unclear; it is believed that fibroblasts arise as a consequence of alveolar epithelial damage. 2 There are 2 types of ossification: idiopathic and secondary to pulmonary lesions.…”

“…Pulmonary ossification is a condition that causes heterotopic ossification of lung tissue. Its manifestations are histologically classified as either nodular or dendriform types; however, the overlap is also common 1. The exact mechanism of action is unclear; it is believed that fibroblasts arise as a consequence of alveolar epithelial damage 2.…”

“…D endriform pulmonary ossification is a subtype of pulmonary ossification that causes ectopic lung tissue ossification. 1 Although the exact mechanism is unclear, it is thought to be caused by fibroblasts associated with lung injury. 2 The ossification can be idiopathic or secondary and is typically observed as linear or branching structures on computed tomography (CT).…”

“…Dendriform pulmonary ossification is a subtype of pulmonary ossification that causes ectopic lung tissue ossification 1. Although the exact mechanism is unclear, it is thought to be caused by fibroblasts associated with lung injury 2.…”