Differential Diagnosis

• Single most likely diagnosis
  • Pneumonia (likely bacterial or fungal): The presence of extensive multifocal consolidation, air bronchograms, and ground-glass opacities with areas of cavitation are highly suggestive of pneumonia. The patient's clinical context, including a known primary malignancy and treatment changes, increases the susceptibility to infections.
• Other Likely diagnoses
  • Metastatic disease: Given the patient's history of primary malignancy, metastatic disease to the lungs is a possibility, especially with the presence of consolidation and volume loss on the right.
  • Treatment-related changes: The mention of treatment changes and the presence of subpleural reticulation on the right suggest that some of the findings could be due to radiation or chemotherapy effects.
  • Bronchiectasis: The probable bronchiectasis on the right, as mentioned, could be a contributing factor to the patient's respiratory symptoms and findings.
• Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
  • Pneumocystis jirovecii pneumonia (PJP): Although not the most likely diagnosis based on the description, PJP is a critical consideration in immunocompromised patients, such as those with malignancies undergoing treatment. It can present with ground-glass opacities and is a potentially life-threatening condition if not promptly treated.
  • Tuberculosis (TB): Given the presence of cavitation and the patient's immunocompromised state, TB is another infection that should not be missed, as it requires specific treatment.
• Rare diagnoses
  • Lymphangitic carcinomatosis: This condition, characterized by the infiltration of lymphatic vessels by metastatic cancer cells, could present with subpleural reticulation and might be considered in the context of a known primary malignancy.
  • Eosinophilic pneumonia: Although less likely, eosinophilic pneumonia could present with consolidation and ground-glass opacities, especially if the patient has a history of eosinophilia or has been exposed to certain drugs or allergens.