What is the likely diagnosis for a chronic smoker and alcoholic patient with a 1-month history of cough, fever, loss of appetite, and weight loss, who has a high-resolution computed tomography (HRCT) scan showing a soft tissue mass causing bronchus cut-off sign, bronchiectatic cavities with air-fluid levels, patchy air space disease, and enlarged pretracheal and subcarinal lymph nodes?

Primary Lung Malignancy with Post-Obstructive Complications

This clinical presentation is highly suspicious for primary bronchogenic carcinoma with post-obstructive pneumonia and abscess formation, requiring urgent tissue diagnosis via bronchoscopy with biopsy and comprehensive staging.

Diagnostic Interpretation

The HRCT findings strongly suggest malignancy as the primary diagnosis based on several key features:

• Soft tissue mass with bronchus cut-off sign indicates an endobronchial or peribronchial tumor causing complete bronchial obstruction 1
• Bronchiectatic cavities with air-fluid levels represent post-obstructive infection and abscess formation distal to the obstructing mass 2
• Patchy airspace disease in multiple lobes suggests either post-obstructive pneumonia or tumor spread 2
• Enlarged mediastinal lymph nodes (pretracheal and subcarinal) indicate likely nodal metastases 1

The patient's risk profile strongly supports this diagnosis:

• Chronic smoking history is the primary risk factor for lung cancer 1
• Constitutional symptoms (weight loss, loss of appetite) over 1 month duration suggest malignancy rather than simple infection 3
• Chronic alcohol use compounds overall cancer risk 3

Critical Diagnostic Pitfalls to Avoid

Do not assume this is simply pneumonia or lung abscess requiring only antibiotics - the bronchus cut-off sign with a soft tissue mass is pathognomonic for an obstructing lesion that must be proven benign or malignant 2. The American College of Radiology emphasizes that persistent consolidation after appropriate antibiotics mandates bronchoscopy to exclude malignancy 2.

Do not delay tissue diagnosis - cough is present in 57% of lung cancer patients, and in chronic smokers with suspicious imaging, malignancy prevalence reaches 1-2% even in chronic cough populations 1. This patient has far more concerning features than isolated chronic cough.

Immediate Diagnostic Workup Required

Mandatory Investigations

• Bronchoscopy with endobronchial biopsy is the definitive next step to visualize the obstructing mass, obtain tissue diagnosis, and assess the degree of airway involvement 2
• Transbronchial needle aspiration (TBNA) of the enlarged mediastinal lymph nodes during bronchoscopy for staging 2
• Sputum cytology (three separate samples) should be sent immediately while awaiting bronchoscopy, though sensitivity is limited 2, 4
• Complete blood count, comprehensive metabolic panel to assess for paraneoplastic syndromes and baseline organ function 2

Staging and Functional Assessment

• PET-CT scan for comprehensive staging once tissue diagnosis confirms malignancy, to identify distant metastases 1
• Pulmonary function tests to assess baseline lung function and surgical candidacy if early-stage disease is confirmed 1
• Brain MRI if neurologic symptoms present or for staging of confirmed non-small cell lung cancer 1

Infection Management

• Broad-spectrum antibiotics covering post-obstructive pneumonia and anaerobic organisms (given cavitation with air-fluid levels) should be initiated immediately 2
• Repeat sputum cultures for bacteria, fungi, and acid-fast bacilli to guide antibiotic therapy and exclude tuberculosis as a confounding diagnosis 2, 4

Differential Considerations (Less Likely)

While the presentation overwhelmingly suggests malignancy, alternative diagnoses to exclude include:

• Tuberculosis - can present with mass-like consolidation, cavitation, and lymphadenopathy, but typically shows upper lobe predominance and different cavity characteristics 4. Three sputum samples for AFB smear and culture are mandatory 2
• Lung abscess from aspiration - chronic alcoholism increases aspiration risk, but would not explain the discrete soft tissue mass or extensive lymphadenopathy 4
• Organizing pneumonia (BOOP) - can present with patchy consolidation and constitutional symptoms, but bronchus cut-off sign and significant lymphadenopathy are atypical 1

Prognostic Considerations

The presence of enlarged mediastinal lymph nodes suggests at minimum N2 disease (stage IIIA or higher), which significantly impacts treatment options and prognosis 1. The National Lung Cancer Screening Trial demonstrated that CT detection of lung cancer provides significant mortality benefit when diagnosed early 1, but this patient's presentation suggests more advanced disease.

Immediate referral to pulmonology for bronchoscopy and to medical oncology for treatment planning is essential - delays in diagnosis directly impact mortality in lung cancer 1.