A 60-year-old woman is brought to the hospital due to progressive shortness of breath and cough for 2 weeks. The patient was diagnosed with right breast cancer and completed radiation therapy 6 weeks ago. Temperature is 37.3 C (99.1 F), blood pressure is 110/70 mm Hg, pulse is 90/min, and respirations are 22/min. Oxygen saturation is 93% on room air. Examination reveals inspiratory crackles over the right lung anteriorly; the lungs are otherwise clear to auscultation. Chest radiograph shows ground-glass opacities in the right lung where radiation was delivered. Laboratory studies reveal no significant changes. Acute radiation-induced lung injury is suspected. Histopathologic examination would most likely reveal formation of which of the following?

Question

A 60-year-old woman is brought to the hospital due to progressive shortness of breath and cough for 2 weeks.  The patient was diagnosed with right breast cancer and completed radiation therapy 6 weeks ago.  Temperature is 37.3 C (99.1 F), blood pressure is 110/70 mm Hg, pulse is 90/min, and respirations are 22/min.  Oxygen saturation is 93% on room air.  Examination reveals inspiratory crackles over the right lung anteriorly; the lungs are otherwise clear to auscultation.  Chest radiograph shows ground-glass opacities in the right lung where radiation was delivered.  Laboratory studies reveal no significant changes.  Acute radiation-induced lung injury is suspected.  Histopathologic examination would most likely reveal formation of which of the following?

Quizplus · Accepted Answer

11ec160b_3b4b_fde8_9249_8980ec2a1d31_MD0001_00 Radiation-induced lung injury usually occurs following thoracic irradiation for the treatment of malignancy (eg, breast or lung cancers, lymphoma). Ionizing radiation causes DNA damage directly (eg, double-strand breaks) and indirectly through generation of reactive oxygen and nitrogen species that can damage both DNA and other cellular components. In the lung, this damage primarily affects the alveolar-capillary barrier, formed from alveolar epithelial cells (ie, pneumocytes) and vascular endothelial cells, and initiates an inflammatory response with a cascade of cytokines (eg, IL-1, TNFα) and growth factors (eg, PDGF, TGF-β). Manifestation vary based on chronicity: Acutely, immune-mediated damage results in impaired gas exchange due to exudative alveolitis, with sloughing of pneumocytes and vascular endothelial cells, alveolar/interstitial edema, and hyaline membrane formation. Clinically, this usually manifests as dyspnea and cough 3-12 weeks after initial radiation exposure. Radiation fibrosis is a delayed manifestation of radiation-induced lung injury that can develop 6-12 months after initial radiation exposure. TGF-β released by immune cells and the surrounding tissue initiates fibroblast proliferation, collagen deposition, and formation of dense fibrous bands. The result is decreased lung volume, dilated bronchi and bronchioles (ie, traction bronchiectasis), impaired mucociliary clearance, and predisposition to chronic infections. (Choices B and C) Hemosiderin-laden macrophages (due to diffuse alveolar hemorrhage) and necrotizing vasculitis are both associated with autoimmune vasculitis (eg, anti-GBM disease). These patients typically have hemoptysis and/or other systemic effects of vasculitis (eg, glomerulonephritis, arthralgias). (Choice D) Although significant neutrophilic infiltrate occurs in patients with radiation-induced lung injury, frank formation of an abscess usually occurs following introduction of anaerobic bacteria to the lung parenchyma due to aspiration (eg, alcohol use disorder) or septic embolism. Educational objective: Radiation-induced lung injury typically occurs following thoracic irradiation (eg, breast cancer), which damages pneumocytes and vascular endothelial cells and initiates an inflammatory response (eg, IL-1, TNFα, TGF-β). This immune response can have both acute (eg, exudative alveolitis, hyaline membrane formation) and delayed (eg, dense fibrosis) effects that typically manifest with cough and dyspnea. __________ References: Radiation-induced lung injury (RILI). (http://www.ncbi.nlm.nih.gov/pubmed/31555602)

A 60-Year-Old Woman Is Brought to the Hospital Due to Progressive