A 65-year-old chronic smoker came to the medicine outpatient department with complaints of upper chest discomfort and drooping of an eyelid. He also complained of pain radiating to the upper arm and a tingling sensation in the 4th and 5th digits of his left hand. The chest X-ray is given below. La d Which of the following is the most likely diagnosis?

Correct Answer: C. Pancoast tumour

Pancoast tumour (superior sulcus lung cancer) is a peripheral lung malignancy arising at the lung apex that invades the brachial plexus, subclavian vessels, and sympathetic chain. The clinical triad presented here is pathognomonic: (1) Horner's syndrome (drooping eyelid = ptosis, from sympathetic chain invasion), (2) Pancoast syndrome (upper chest pain radiating to the arm from brachial plexus involvement, particularly C8–T1 nerve roots), and (3) paresthesias in 4th and 5th digits (ulnar nerve distribution, confirming lower brachial plexus compression). The patient's smoking history and apical lung lesion on CXR complete the picture. Pancoast tumours account for 3–5% of all lung cancers but are the classic cause of this neurovascular syndrome. The diagnosis is confirmed by CT chest with contrast and tissue biopsy. Indian guidelines (RNTCP) classify this as locally advanced NSCLC requiring multimodal therapy (neoadjuvant chemotherapy + surgery ± radiotherapy).

Why the other options are wrong

A. Superior vena cava obstruction — SVC obstruction presents with facial plethora, neck vein distension, and upper limb oedema—none of which are described here. While Pancoast tumour can cause SVC obstruction, the specific neurological findings (Horner's + brachial plexus pain + ulnar paresthesias) point directly to apical tumour invasion, not just venous compression. This is an NBE trap for students who focus only on 'chest discomfort' without integrating the neurological syndrome. B. Upper lobe pneumonia — Pneumonia presents acutely with fever, productive cough, and systemic toxicity—none mentioned here. The chronic presentation, smoking history, and insidious neurological deficits (Horner's, brachial plexus syndrome) indicate a malignancy, not infection. CXR findings in pneumonia are consolidation with air bronchograms, not the apical mass typical of Pancoast tumour. This option tests whether students conflate upper lobe pathology with infection. D. Aspergilloma — Aspergilloma (fungal ball in pre-existing cavity) occurs in patients with prior TB or cavitary lung disease and presents with haemoptysis, not Horner's syndrome or brachial plexus neuropathy. While aspergilloma can occur in smokers with COPD, it does not cause the characteristic neurovascular syndrome described. The absence of haemoptysis and the specific neurological findings exclude this diagnosis.

High-Yield Facts

Mnemonics

PANCOAST Syndrome Pain (upper chest/arm), Arm paresthesias (ulnar), Neurological (Horner's), Cancer (apical), Occurs in smokers, Apex location, Superior sulcus, Tumour (NSCLC). Use when you see Horner's + brachial plexus pain in a smoker. Horner's Triad in Pancoast Ptosis (drooping lid), Miosis (small pupil), Anhidrosis (no sweating on forehead). Remember: sympathetic chain at T1 is invaded by apical tumour. Use to confirm the neurological component.

NBE Trap

NBE pairs 'upper chest discomfort' with SVC obstruction to distract from the neurological syndrome (Horner's + brachial plexus neuropathy) that is pathognomonic for Pancoast tumour. Students who focus only on vascular symptoms miss the key discriminator: the specific nerve root involvement (C8–T1 ulnar distribution).

Clinical Pearl

In Indian tertiary centres, Pancoast tumour is often diagnosed late because the neurological symptoms are initially attributed to cervical spondylosis or brachial neuritis. Always suspect apical malignancy in a chronic smoker with Horner's syndrome + ulnar nerve symptoms, even without prominent respiratory complaints. Early imaging and biopsy can enable multimodal therapy and improve survival.

_Reference: Harrison Ch. 85 (Lung Cancer); Robbins Ch. 15 (Lung Neoplasms); KD Tripathi Ch. 12 (Anticancer Drugs)_