TRAPPED LUNG AS A COMPLICATION OF PLEURAL METASTASES FROM SQUAMOUS CELL CARCINOMA OF BUCCAL MUCOSA

Abstract

TOPIC: Disorders of the Pleura TYPE: Medical Student/Resident Case Reports INTRODUCTION: Trapped lung is an uncommon complication of malignant pleural effusion (MPE). It presents as post-thoracentesis hydropneumothorax (known as pneumothorax ex vacuo, PEV) or pleural effusion that cannot be completely drained due to development of chest pain [1]. It is important to recognize PEV, as although it may appear alarming, it is an asymptomatic process that is not amenable to chest tube placement. CASE PRESENTATION: 60 year old male with squamous cell carcinoma (SCC) of buccal mucosa for which he underwent surgery with radiotherapy 2 years ago, presented with 1 week of dyspnea. Chest X-ray showed a large right-sided pleural effusion with ipsilateral displacement of mediastinum [Figure 1]. He underwent thoracentesis but procedure was terminated prematurely due to development of chest pain. Post-thoracentesis CT chest [Figure 2] to evaluate for underlying lung pathology showed pleural thickening. Fluid cytology was positive for malignant squamous cells. He subsequently underwent thoracoscopy showing extensive involvement of visceral and parietal pleural surfaces with malignant appearing lesions. Pleural biopsies, done to obtain more tissue for next generation sequencing, were consistent with malignant squamous cells. An indwelling pleural catheter was placed at the end of the procedure for long term management of his malignant pleural effusion. Post-procedure chest X-ray showed a partially expanded right lung with a large PEV [Figure 3]. The patient was asymptomatic at this point with good oxygenation on room air. Pleural manometry was performed using a digital pleural manometer showing a negative pleural pressure. DISCUSSION: Pleura is a relatively rare site of metastases from head and neck SCC [2]. Trapped lung can develop due to pleural adhesions or involvement of visceral pleura with malignant lesions [3]. Diagnosis should be suspected when chest x-ray shows large pleural effusion with ipsilateral shift of mediastinum as was seen in our patient. The patients may also have chest pain with drainage of pleural effusion. Effective management of trapped lung and PEV in MPEs remains challenging. Various treatment modalities exist, including minimally invasive procedures such as thoracocentesis or indwelling pleural catheters, as well as invasive procedures such as pleuroperitoneal shunt, thoracotomy, and decortication. The optimal treatment approach should balance therapeutic benefit versus required period of convalescence for a disease with poor life expectancy [4]. CONCLUSIONS: We present a rare complication (PEV from trapped lung) in a relatively rare disease process (pleural metastases in head and neck cancer). In cases of pneumothorax after pleural drainage, it is important to consider PEV due to trapped lung as it will direct treatment approaches. REFERENCE #1: Huggins JT, Doelken P, Sahn SA. The unexpandable lung. F1000 Med Rep. 2010;2:77. Published 2010 Oct 21. doi:10.3410/M2-77 REFERENCE #2: Ferlito A, Shaha AR, Silver CE, Rinaldo A, Mondin V. Incidence and sites of distant metastases from head and neck cancer. ORL J Otorhinolaryngol Relat Spec. 2001 Jul-Aug;63(4):202-7. doi: 10.1159/000055740. PMID: 11408812 REFERENCE #3: Petrov, D., Mihalova, T., Valchev, D.. Malignant pleural effusions and trapped lung. AME Medical Journal, North America, 5, mar. 2020. Available at: <https://amj.amegroups.com/article/view/5466> DISCLOSURES: No relevant relationships by Sudeepthi Bandikatla, source=Web Response No relevant relationships by James Bradley, source=Web Response No relevant relationships by Apaar dadlani, source=Web Response No relevant relationships by Umair Gauhar, source=Web Response No relevant relationships by Vatsala Katiyar, source=Web Response No relevant relationships by Adam Rojan, source=Web Response