A 45-year-old businessman was hospitalized for 5 days for dengue fever in 2011 during the peak of a dengue epidemic in Pakistan. He was managed with supportive treatment. Other than controlled hypertension, his past medical and family histories were unremarkable. A week post-discharge, he re-presented with left-sided chest pain, exertional dyspnoea, cough and a medium-sized, multi-loculated left-sided pleural effusion. Baseline haematological, coagulation and biochemical profiles were normal. A diagnostic pleural aspiration revealed a straw-coloured lymphocyte-predominant exudate. Bronchoscopy and bronchial washings were non-informative. A closed Abrams' biopsy yielded only non-specific pleural inflammation. A chest tube was inserted and 1.3 L of fluid was removed. In accordance with local practice for undiagnosed lymphocytic effusions, he was given an empirical trial of quadruple anti-tuberculosis (TB) therapy for TB pleuritis which he took for 4 months before being lost to follow-up.
He re-presented in June 2015 with "heaviness" in his chest. A chest X-ray (CXR) and computed tomography (CT; Fig. 1) showed a large left-sided pleural-based low-density mass resembling a pleural effusion. The previous loculated residual pleural fluid collections had resolved. There was visceral pleural thickening but no abnormality was seen in the lung parenchyma or cardiovascular structures. He underwent a video-assisted thoracoscopic surgery (VATS), which identified a huge, firm-to-hard, pleural-based mass that was completely excised following conversion to a thoracotomy. The mass (Fig. 2A), which weighed 2.2 kg, occupied the anterior mediastinal recess at the level of left internal mammary artery and involved the second and third intercostal recessions. The mass was parietal pleural-based but also extended into the chest wall and was adherent to the visceral pleura, thus requiring non-anatomical lung resection for removal. The histopathology was unusual. An opinion was sought from the multi-disciplinary thoracic oncology meeting of a quaternary centre of pleural disease/mesothelioma. Tissue block and slides were examined by a specialist pleural pathologist (S. M. Chai).
The morphology and immunohistochemistry of the tumour were diagnostic for desmoid-type fibromatosis. The lesional tissue showed bland spindle-shaped cells arranged in intersecting fascicles (Fig. 2B). The cells were set in variably dense collagenous stroma, with patches of myxoid change. The spindle-shaped cells had oval nuclei, small nucleoli and delicate pale eosinophilic to amphophilic cytoplasm. Scattered mitotic figures were present without any necrosis or cellular atypia. At the periphery of the tumour, the spindle-shaped cells infiltrated and surrounded individual skeletal muscle fibres. There was patchy cytoplasmic staining for smooth muscle actin and nuclear staining for beta-catenin (Fig. 2C). The lesional cells were negative for desmin, S-100, calretinin, MNF 116, D2-40, AE1 + 3, CK7 and CD34 immunostains.
The patient made an uneventful recovery and had no signs of tumour recurrence after 9 months of follow-up.