CRA19 LIQUEFIED LUNG CANCER: AN UNCOMMON FORM OF SQUAMOUS CELL CARCINOMA OF THE LUNG

Fion Suet Li Liew¹, Boon Hau Ng¹, Nor Safiqah Sharil², Rose Azzlinda Osman¹, Hsueh Jing Low³, Nik Nuratiqah Nik Abeed¹, Andrea Yu-Lin Ban¹
1Respiratory Unit, Department of Medicine, Faculty of Medicine, Universiti Kebangsaan Malaysia, Hospital Canselor Tuanku Muhriz, Kuala Lumpur, Malaysia.
2Department of Anesthesiology and Critical Care, Faculty of Medicine, Universiti Kebangsaan Malaysia, Hospital Canselor Tuanku Muhriz, Kuala Lumpur, Malaysia.
3Internal Medical Unit, Faculty of Medicine and Health Science, Universiti Sains Islam Malaysia, Nilai, Negeri Sembilan.

Introduction
Lung abscesses most commonly result from microbial infections. They typically develop in the setting of aspiration, impaired host immunity, or secondary to necrotising pneumonia, and they often show favourable clinical response to appropriate antibiotic therapy. However, in cases where there is poor response to medical treatment or persistent radiological abnormalities, alternative diagnoses must be considered. Among these, underlying malignancy is an important differential diagnosis that should not be overlooked.

Case report
A 83-year-old man presented with a two-week history of cough and fever. He was initially managed at another centre for left lung abscess and completed a six-week course of antibiotics. Initial computed tomography (CT) thorax revealed a large, thick-walled, fluid-filled cavitary lesion in the left lower lobe measuring 7.5 × 6 × 8.7 cm. A follow-up CT scan of the thorax showed persistence and recurrence of the collection, prompting chest drainage. Cultures, mycobacterial studies, and cytology of the drained fluid were all negative. Despite an additional course of inpatient intravenous antibiotics, a subsequent thoracic ultrasound revealed a large heterogeneous hypoechoic mass. Ultrasound-guided biopsy of the lesion confirmed the diagnosis of squamous cell carcinoma (SCC).

Discussion
Cavitation occurs in 10–22% of SCC cases due to rapid tumor growth outpacing its blood supply, leading to necrosis. Distinguishing between a cavitating malignancy and an infectious abscess can be difficult. However, CT features such as wall thickness ≤4 mm suggest a benign process, while thickness ≥15 mm is more indicative of malignancy. Failure of a lung abscess to resolve with appropriate antibiotics warrants further evaluation, including biopsy, to exclude underlying cancer. Liquefied lung carcinoma carries a poor prognosis due to frequent vascular invasion, early metastasis, and diagnostic delays. Early suspicion is key to improving outcomes.