Selected case from the Arkadi M. Rywlin international pathology slide series: Diffuse dendriform pulmonary ossification: Report of 2 cases with review of the literature

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.