A rare etiology of pulmonary nodules

Our plain-English summary of A rare etiology of pulmonary nodules, by A. Rupal, H. Singh, C. Jani, et al (Respiratory Medicine Case Reports, 2021).

The study

• Authors: A. Rupal, H. Singh, C. Jani, O. Al Omari, D. Patel, J. Perry, C.C. Thomson
• Journal: Respiratory Medicine Case Reports
• Published: 2021;34:101519
• Type of article: Case report
• Cited by: 5 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Introduction: Pulmonary nodules are a frequent finding on chest imaging studies, with differential including multiple benign entities, but malignancy is often also a concern. Computed Tomography (CT) and Fluorodeoxyglucose (FDG)-Positron Emission Tomography (PET) scans have improved the characterization of pulmonary nodules. However, many nodules remain indeterminate and require periodic monitoring. Here we report two nodular pulmonary amyloidosis cases as a rare etiology of enlarging pulmonary nodules with FDG avidity.

Case Presentation: Case 1: 75-year-old woman with a history of asthma, emphysema, bronchiectasis, and a 48 pack-year smoking history was found to have subcentimeter groundglass pulmonary nodules in the right lower lobe (RLL). Follow-up imaging demonstrated an increased solid component of a RLL bulla associated with mild FDG uptake on PET scan. A CT-guided biopsy revealed amyloid deposition. Case 2: 77-year-old man with a history of interstitial lung disease, asbestos exposure, prior tobacco use, and atrial fibrillation treated with amiodarone was found to have a 1.6cm RLL nodule. Follow-up imaging identified an interval increase to 2.0cm associated with moderate FDG uptake on PET scan. Transthoracic biopsy identified amyloid deposition.

Discussion: Nodular pulmonary amyloidosis is a rare form of amyloidosis which may present as an enlarging pulmonary nodule with FDG avidity, raising concern for malignancy. A CT-guided biopsy is a safe way to establish a diagnosis. Recent studies have demonstrated an association between nodular pulmonary amyloidosis and marginal zone lymphomas, which warrants longitudinal follow-up for evolution to lymphoproliferative disorder.

© 2021 The Authors.

In plain English

This article is a case series of two patients whose growing lung nodules turned out to be nodular pulmonary amyloidosis, a rare benign condition in which abnormal protein deposits build up in the lung. The first, a 75-year-old woman with a 48 pack-year smoking history, had a right lower lobe nodule with mild PET-scan uptake (maximum SUV 0.5). Biopsy showed amyloid. The authors wrote that her bone marrow findings were felt to reflect a likely pulmonary marginal zone lymphoma, but they also gave a final diagnosis without an underlying lymphoproliferative disorder. Her nodule did not change significantly over two years. The second, a 77-year-old man with asbestos exposure, pleural plaques, interstitial lung disease and past smoking, had a right lower lobe nodule that grew from 1.6 cm to 2 cm, with moderate PET uptake (maximum SUV 4.1). Biopsy showed AL (kappa) type amyloid. The nodule reached 2.4 cm and then stayed unchanged for 2 years. The article did not discuss asbestos as a cause of the amyloidosis. The authors concluded that this condition can appear as an enlarging nodule that takes up PET tracer, and that diagnosis requires tissue biopsy.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: case series (two case reports)
• Who was studied: Two patients: a 75-year-old woman with asthma, emphysema, bronchiectasis and a 48 pack-year smoking history, and a 77-year-old man with interstitial lung disease, asbestos exposure, pleural plaques and past smoking. The article gives no study location or dates for the patients.
• Exposure: Only the second patient had a history of asbestos exposure (no fiber type, job or dose given), along with pleural plaques, prior tobacco use (7 pack-years) and amiodarone treatment. The figure legend attributes a calcified pleural plaque to the asbestos exposure.
• Main results:
  • Case 1 (woman): the right lower lobe lesion showed mild FDG uptake, maximum SUV 0.5, on PET.
  • Case 1: biopsy of the lesion showed amyloid deposition and plasma cells.
  • Case 1: bone marrow flow cytometry showed a small (2%) kappa-restricted B-cell population and a less than 1% kappa-restricted plasma cell population. These were felt to represent marrow involvement by a likely pulmonary marginal zone lymphoma.
  • Case 1: there was no evidence of systemic amyloidosis, and a final diagnosis of nodular pulmonary amyloidosis was made.
  • Case 1: after slight enlargement following biopsy, the nodule was followed for two years without significant change in size.
  • Case 2 (man): the right lower lobe nodule grew from 1.6 cm to 2 cm.
  • Case 2: PET-CT showed moderate FDG uptake (max SUV 4.1) in the lung lesion and increased uptake (max SUV 5.9) in calcified prevertebral lymph nodes.
  • Case 2: transthoracic biopsy showed amyloid deposition, of AL (kappa) type.
  • Case 2: blood testing showed a monoclonal IgM kappa band and a kappa lambda ratio of 1.88.
  • Case 2: no intervention was indicated. The nodule grew to 2.4 cm and then remained unchanged for 2 years.
• The authors' conclusion: The authors concluded that nodular pulmonary amyloidosis is a rare benign cause of lung nodules that may present as an enlarging nodule with FDG uptake, and that diagnosis requires tissue biopsy showing amyloid on Congo-red staining.

Topics

Medical terms in this study, explained in our Lexicon: Etiology, Emphysema, PET Scan, Biopsy, Deposition, Interstitial Lung Disease, Asbestos Exposure.

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• Solitary pulmonary nodule malignancy predictive models applicable to routine clinical practice: a systematic review — M. Senent-Valero, J. Librero, et al. (2021)
• Diffuse intrapulmonary malignant mesothelioma presenting with miliary pulmonary nodules: A case report — T. Hida, M. Hamasaki, et al. (2015)
• Solitary pulmonary nodule in a patient without asbestos exposure — J.F. Turner, C. Gronbeck, et al. (1992)
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