Unusual Presentation of Cryptogenic Organising Pneumonia as a Focal Lung Mass: A Case Report and Literature Review.

Organising pneumonia (OP) is a distinct pathological pattern characterised by the presence of granulation tissue buds composed of fibroblasts and myofibroblasts embedded in a loose connective tissue matrix within the distal pulmonary airspaces. When OP occurs without an identifiable cause or etiologic context, it is termed cryptogenic organising pneumonia (COP). The diagnosis of OP can be challenging due to its diverse clinical presentations, including the idiopathic form and various secondary forms associated with underlying diseases. We report a case of a middle-aged male presenting with intermittent cough and haemoptysis. Initial sputum analysis was unremarkable, and the patient showed no improvement with antibiotic therapy. Chest radiography showed left lower zone consolidation. Computed tomography (CT) thorax revealed a mass in the left lower lobe, while positron emission tomography-computed tomography (PET/CT) demonstrated a hypermetabolic lesion at the same site. Bronchoscopic bronchoalveolar lavage was negative for tuberculosis, respiratory pathogens, and malignancy. Autoimmune screening yielded negative results. A transthoracic tru-cut lung biopsy confirmed the diagnosis of OP. The patient was treated with prednisolone, leading to significant clinical improvement and complete resolution of the lesion on follow-up CT imaging.