Dendriform Pulmonary Ossification in the Absence of Usual Interstitial Pneumonia: CT Features and Possible Association With Recurrent Acid Aspiration

Idiopathic dendriform pulmonary ossification as the phenotype of interstitial lung abnormalities: CT-pathologic correlation and prevalence

BACKGROUND AND PURPOSE

Idiopathic dendriform pulmonary ossification (DPO) is mostly asymptomatic, and detected incidentally in lung CT. There have been no reports on the precise CT-pathologic correlation and the prevalence of idiopathic DPO. This study aimed to clarify the histological background and prevalence of idiopathic DPO.

MATERIALS AND METHODS

Sixteen patients with histologically confirmed idiopathic DPO (12 men and 4 women; mean age, 38.8 years; range 22-56 years) were identified in a nationwide epidemiological survey. Local HRCT findings of pre-biopsy examinations, such as branching, round, linear structures with or without high attenuation were compared side by side with histological findings. The attenuation of branching, round, and linear structures was classified into three-point levels on bone window images (width, 2500 HU; level, 500 HU). Furthermore, we collected continuous pulmonary CT images of 8111 cases for checking up metastasis from extrathoracic malignancy at a single institution, and evaluated the prevalence of interstitial lung abnormalities (ILAs) and DPO.

RESULTS

In all 16 cases, branching (n = 15, 93%), round (n = 5, 31%), or linear (n = 5, 31%) structures were identified, histologically corresponding to dendriform ossification and cicatricial organizing pneumonia (OP)/fibrosis. Histologically, ossification was confirmed in all the 16 patients. However, in two cases, a highly attenuated structure could not be detected on the pre-biopsy CT of the same area. Regarding the prevalence of idiopathic DPO, 283 (3.5%) of 8111 patients had ILAs, of which a total of 26 (0.3% of all cases, 9.2% of ILAs cases) had DPO.

CONCLUSION

Idiopathic DPO showed linear or branching structures with or without high attenuation on CT, corresponded to ossification, cicatricial OP/fibrosis. DPO was seen in 9.2% of ILAs cases. Idiopathic DPO is one of pathologic phenotypes of ILAs.

Chronic Aspiration as a Cause for Dendriform Pulmonary Ossifications

Teaching point: Dendriform pulmonary ossifications (DPO) are a rare form of diffuse pulmonary ossifications, in which these ossifications are organised in dendrite-like lines in the periphery of the bases of the lung, most commonly attributed to underlying interstitial lung disease (ILD), but can also be found in patients with chronic aspiration if no other CT findings of ILD are present.

Central Role of CT in Management of Pulmonary Fibrosis

With the approval of antifibrotic medications to treat patients with idiopathic pulmonary fibrosis and progressive pulmonary fibrosis, radiologists have an integral role in diagnosing these entities and guiding treatment decisions. CT features of early pulmonary fibrosis include irregular thickening of interlobular septa, pleura, and intralobular linear structures, with subsequent progression to reticular abnormality, traction bronchiectasis or bronchiolectasis, and honeycombing. CT patterns of fibrotic lung disease can often be reliably classified on the basis of the CT features and distribution of the condition. Accurate identification of usual interstitial pneumonia (UIP) or probable UIP patterns by radiologists can obviate the need for a tissue sample-based diagnosis. Other entities that can appear as a UIP pattern must be excluded in multidisciplinary discussion before a diagnosis of idiopathic pulmonary fibrosis is made. Although the imaging findings of nonspecific interstitial pneumonia and fibrotic hypersensitivity pneumonitis can overlap with those of a radiologic UIP pattern, these entities can often be distinguished by paying careful attention to the radiologic signs. Diagnostic challenges may include misdiagnosis of fibrotic lung disease due to pitfalls such as airspace enlargement with fibrosis, paraseptal emphysema, recurrent aspiration, and postinfectious fibrosis. The radiologist also plays an important role in identifying complications of pulmonary fibrosis-pulmonary hypertension, acute exacerbation, infection, and lung cancer in particular. In cases in which there is uncertainty regarding the clinical and radiologic diagnoses, surgical biopsy is recommended, and a multidisciplinary discussion among clinicians, radiologists, and pathologists can be used to address diagnosis and management strategies. This review is intended to help radiologists diagnose and manage pulmonary fibrosis more accurately, ultimately aiding in the clinical management of affected patients. ©RSNA, 2024 Supplemental material is available for this article.

Stepwise diagnostic algorithm for high-attenuation pulmonary abnormalities on CT

High-attenuation pulmonary abnormalities are commonly seen on CT. These findings are increasingly encountered with the growing number of CT examinations and the wide availability of thin-slice images. The abnormalities include benign lesions, such as infectious granulomatous diseases and metabolic diseases, and malignant tumors, such as lung cancers and metastatic tumors. Due to the wide spectrum of diseases, the proper diagnosis of high-attenuation abnormalities can be challenging. The assessment of these abnormal findings requires scrutiny, and the treatment is imperative. Our proposed stepwise diagnostic algorithm consists of five steps. Step 1: Establish the presence or absence of metallic artifacts. Step 2: Identify associated nodular or mass-like soft tissue components. Step 3: Establish the presence of solitary or multiple lesions if identified in Step 2. Step 4: Ascertain the predominant distribution in the upper or lower lungs if not identified in Step 2. Step 5: Identify the morphological pattern, such as linear, consolidation, nodular, or micronodular if not identified in Step 4. These five steps to diagnosing high-attenuation abnormalities subdivide the lesions into nine categories. This stepwise radiologic diagnostic approach could help to narrow the differential diagnosis for various pulmonary high-attenuation abnormalities and to achieve a precise diagnosis.Critical relevance statement Our proposed stepwise diagnostic algorithm for high-attenuation pulmonary abnormalities may help to recognize a variety of those high-attenuation findings, to determine whether the associated diseases require further investigation, and to guide appropriate patient management. Key points • To provide a stepwise diagnostic approach to high-attenuation pulmonary abnormalities.• To familiarize radiologists with the varying cause of high-attenuation pulmonary abnormalities.• To recognize which high-attenuation abnormalities require scrutiny and prompt treatment.

Diffuse pulmonary ossification: A case report unveiling clinical and histopathological challenges

Diffuse pulmonary ossification (DPO) is a rare pulmonary condition characterized by the diffuse formation of mature bone in the lungs. Pulmonary ossification, in general, can be subdivided into diffuse pulmonary ossification (DPO) and nodular pulmonary ossification (NPO). DPO occurs most commonly in the settings of chronic pulmonary conditions; however, idiopathic cases have been reported. We present a case of DPO in a 36-year-old man with progressive exertional dyspnea, productive cough, and occasional hemoptysis. Imaging studies showed innumerable pulmonary nodules scattered throughout both lungs. Initially, the diagnoses of pulmonary alveolar microlithiasis (PAM) or, less likely miliary tuberculosis (TB) were considered. However, Quantiferon TB test was negative and genetic testing was negative for SLC34A2, lowering the probability of PAM. The patient underwent a segmentectomy. Microscopic examination showed ramifying spicules of mature woven bone and fatty marrow consistent with DPO. There were no significant underlying pathologic findings, such as interstitial fibrosis, granulomas, organizing pneumonia, or significant inflammation in the background lung parenchyma. In conclusion, clinicians and radiologists need to be aware of DPO in the differential diagnosis of miliary tuberculosis and pulmonary alveolar microlithiasis. The absence of an underlying chronic pulmonary condition does not exclude the possibility of DPO.

Pathogenesis of Pulmonary Calcification and Homologies with Biomineralization in Other Tissues

Lungs often present tissue calcifications and even ossifications, both in the context of high or normal serum calcium levels. Precise mechanisms governing lung calcifications have not been explored. Herein, we emphasize recent advances about calcification processes in other tissues (especially vascular and bone calcifications) and discuss potential sources of calcium precipitates in the lungs, involvement of mineralization promoters and crystallization inhibitors, as well as specific cytokine milieu and cellular phenotypes characteristic for lung diseases, which may be involved in pulmonary calcifications. Further studies are necessary to demonstrate the exact mechanisms underlying calcifications in the lungs, document homologies in biomineralization processes between various tissues in physiological and pathologic conditions, and unravel any locally specific characteristics of mineralization processes that may be targeted to reduce or prevent functionally relevant lung calcifications without negatively affecting the skeleton.

Proceedings of the 2022 National Toxicology Program Satellite Symposium

The 2022 annual National Toxicology Program Satellite Symposium, entitled "Pathology Potpourri," was held in Austin, Texas at the Society of Toxicologic Pathology's 40th annual meeting during a half-day session on Sunday, June 19. The goal of this symposium was to present and discuss challenging diagnostic pathology and/or nomenclature issues. This article presents summaries of the speakers' talks along with select images that were used by the audience for voting and discussion. Various lesions and topics covered during the symposium included induced and spontaneous neoplastic and nonneoplastic lesions in the mouse lung, spontaneous lesions in the reproductive tract of a female cynomolgus macaque, induced vascular lesions in a mouse asthma model and interesting case studies in a rhesus macaque, dog and genetically engineered mouse model.

Nothing but lung and bones: Longitudinal evolution and quantitative analysis in a case of idiopathic diffuse pulmonary ossification

A 77-year-old Caucasian man, a former surveyor in a chemical company, underwent a chest X-ray (CXR) as a follow-up exam for a melanoma of the back, surgically removed.

CXR showed interstitial thickening in both lower lobes; then, a high-resolution computed tomography of the chest (HRCT) was performed to further investigate these findings, revealing multiple small, calcified nodules with branching appearance at both lung bases.

Clinical examination and exposure history were negative, except for a decrease in diffusing capacity for carbon monoxide resulting from pulmonary function tests.

Surgical lung biopsy was performed; histology revealed numerous nodules and branching tubules of bone tissue, some of which with marrow elements.

After multidisciplinary discussion of the case, a diagnosis of idiopathic diffuse pulmonary ossification (DPO) was considered.

Clinical status of the patient was stable over time, despite the increase in extent of calcifications.

DPO is an uncommon condition that should be considered in different clinical-radiological settings; multidisciplinary discussion is essential for the final diagnosis.

Lung transplant for pulmonary fibrosis with dendriform ossification

Dendriform pulmonary ossification (DPO) is a rare condition defined as disseminated, widespread heterotopic bone formation within the lungs. This condition is associated with restrictive pulmonary disease, such as interstitial pneumonia or fibrosis. The clinical features and pathophysiology of DPO, however, remain unclear. We report a case of a 66-year-old male with idiopathic pulmonary fibrosis accompanied by DPO who was treated with a double lung transplant. His postoperative course was uneventful without recurrence of DPO.

A case of diffuse pulmonary ossification

Diffuse pulmonary ossification (DPO) is a rare condition characterized by the formation of bone tissues in the lung. DPO is considered to be accompanied by chronic lung diseases, such as idiopathic interstitial pneumonitis or chronic obstructive pulmonary disease, acute respiratory distress syndrome, or inhalation-related lung diseases. Most reported cases of DPO were diagnosed during autopsies or surgical specimen. We report a case of DPO after kidney transplantation diagnosed by transbronchial lung biopsy.

Chronic cough with dual pathologies of pulmonary ossification

An 81-year-old man presented with chronic cough, which did not respond to the initiation of combined bronchodilator/inhaled corticosteroid therapy. CT of the chest revealed calcified nodules throughout the trachea sparing the posterior membrane, and tiny peripheral parenchymal nodules with basal interlobular septal thickening and calcification. Flexible bronchoscopy demonstrated endobronchial nodularity from the proximal trachea to the mid-sections of both main bronchi, sparing the posterior membrane. Histopathology revealed submucosal fibrous connective tissue and benign bone, confirming a diagnosis of tracheobronchopathia osteochondroplastica. CT was consistent with a concurrent diagnosis of dendriform pulmonary ossification. These two rare phenomena often present with non-specific symptoms, and the diagnosis can be made with imaging in both conditions. There is a role for bronchoscopy in the diagnosis of tracheobronchopathia osteochondropastica, and the endobronchial appearance could be diagnostic. The concurrence of both phenomena in our case might represent activity of a common cellular pathway of ossification in both sites.

Histologically Proven Dendriform Pulmonary Ossification: A Five-case Series

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.

Bilateral Diffuse Nodular Pulmonary Ossification Mimicking Metastatic Disease in a Patient with Fibrolamellar Hepatocellular Carcinoma

Pulmonary ossification (PO) is a rare finding, characterized by mature bone formation in the lung parenchyma. We report a 20-year-old female patient diagnosed with fibrolamellar hepatocellular carcinoma (FL-HCC) and bilateral diffuse nodular PO. The patient presented with a unifocal left liver mass and multiple bilateral pulmonary lesions, which were treated as metastatic disease. The patient received neoadjuvant chemotherapy, followed by left hepatectomy, and bilateral staged thoracotomies for clearance of the pulmonary disease. The histology of the pulmonary nodules demonstrated nodular type PO. We present the history, the course of treatment, imaging, and histologic findings of this rare disease process that could mimic metastatic pulmonary disease.

Radiological honeycombing: pitfalls in idiopathic pulmonary fibrosis diagnosis

INTRODUCTION

High-Resolution Computed Tomography (HRCT) plays a pivotal role in the diagnosis of Idiopathic Pulmonary Fibrosis (IPF). First, it establishes the presence of lung fibrosis. Second, it allows the recognition of specific patterns, namely typical and probable Usual Interstitial Pneumonia (UIP) pattern obviating the need for tissue confirmation in the appropriate clinical context.

AREAS COVERED

Acknowledging the extreme versatility of modern radiology and the heavy burden of knowledge the modern radiologist has to cope with, this review addresses the diagnostic pitfalls of honeycombing in IPF diagnosis. This review focuses on two areas: i) when honeycombing is actually present but there are other findings that should raise suspicion of an alternative diagnosis and ii) when honeycombing is misdiagnosed, focusing on the commonest radiographic patterns that are responsible for this confusion.

EXPERT OPINION

It is pivotal to establish the actual presence of honeycombing. Even then, the distribution of honeycombing or the presence of other findings could be suggestive of alternative diagnoses. Reviewing older images can be extremely helpful in reaching the correct diagnosis.

Cicatricial Organizing Pneumonia with Dendriform Pulmonary Ossification: An Unusual Cause for a Recurrent Pneumothorax

Cicatricial organizing pneumonia is an uncommon form of organizing pneumonia, which may manifest as persisting linear opacities on computerized tomography (CT) scan mimicking a fibrosing interstitial pneumonia. It may also manifest with pulmonary ossification, which is a metaplastic bone formation within the lung tissue. The latter presentation could be either nodular or dendriform, both secondary to underlying lung disease and rarely idiopathic. Dendriform pulmonary ossification (DPO) has rarely been described as a cause of spontaneous pneumothorax. We present a case of a 55-year-old male with history of recurrent pneumothoraces and worsening dyspnea on exertion. A CT of the chest revealed progressive bilateral sub-pleural and peribronchovascular reticular opacities associated with densely ossified branching and nodular opacities. Video-assisted thoracoscopic biopsy of the lung demonstrated cicatricial organizing pneumonia with areas of marked diffuse DPO. The case highlights that dendriform pulmonary ossification arising from cicatricial organizing pneumonia should be considered in the differential diagnosis of recurrent pneumonias among patients with lower lobe sub-pleural reticular opacities. The case highlights that dendriform pulmonary ossification rarely can cause spontaneous pneumothorax and can be associated with cicatricial organizing pneumonia and reticular opacities on imaging.

An Algorithmic Approach to the Interpretation of Diffuse Lung Disease on Chest CT Imaging: A Theory of Almost Everything

We propose an algorithmic approach to the interpretation of diffuse lung disease on high-resolution CT. Following an initial review of pertinent lung anatomy, the following steps are included. Step 1: a preliminary review of available chest radiographs, including the "scanogram" obtained at the time of the CT examination. Step 2: a review of optimal methods of data acquisition and reconstruction, emphasizing the need for contiguous high-resolution images throughout the entire thorax. Step 3: initial uninterrupted scrolling of contiguous high-resolution images throughout the chest to establish the quality of examination as well as an overview of the presence and extent of disease. Step 4: determination of one of three predominant categories - primarily reticular disease, nodular disease, or diseases associated with diffuse alteration in lung density. Based on this determination, one of the three following Steps are followed: Step 5: evaluation of cases primarily involving diffuse lung reticulation; Step 6: evaluation of cases primarily resulting in diffuse lung nodules; and Step 7: evaluation of cases with diffuse alterations in lung density including those with diffusely diminished lung density vs those with heterogenous or diffusely increased lung density, respectively. It is anticipated that this algorithmic approach will substantially enhance initial interpretations of a wide range of pulmonary disease.