A 65-year-old patient who completed radiotherapy for breast cancer 4 months ago presents with dry cough and low-grade fever. CT chest shows a non-segmental area of consolidation with ground-glass opacity confined strictly to the radiation port, with straight geometric margins. Which of the following is the most likely diagnosis?
- A Recurrent breast carcinoma with pulmonary spread
- B Radiation pneumonitis ✓
- C Community-acquired pneumonia
- D Drug-induced pneumonitis from chemotherapy
Correct answer: B. Radiation pneumonitis
Explanation
Radiation pneumonitis typically occurs 1-6 months after radiotherapy and is characterized by ground-glass opacity or consolidation confined to the radiation port with straight geometric margins corresponding to the radiation field. This geometric demarcation is the key distinguishing feature. Recurrent carcinoma would show nodules or effusion. Community-acquired pneumonia does not respect radiation field boundaries. Drug-induced pneumonitis is usually more diffuse and bilateral.
Reference: Grainger & Allison's Diagnostic Radiology, 7th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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