Potential Pitfall in the Assessment of Lung Cancer with FDG-PET/CT: Talc Pleurodesis Causes Intrathoracic Nodal FDG Avidity

Objective. Talc pleurodesis is a common procedure performed to treat complications related to lung cancer. The purpose of our study was to characterize any thoracic nodal findings on FDG PET/CT associated with prior talc pleurodesis. Materials and Methods. The electronic medical record identified 44 patients who underwent PET/CT between January 2006 and December 2010 and had a history of talc pleurodesis. For each exam, we evaluated the distribution pattern, size, and attenuation of intrathoracic lymph nodes and the associated standardized uptake value. Results. High-attenuation intrathoracic lymph nodes were noted in 11 patients (25%), and all had corresponding increased FDG uptake (range 2–9？mm). Involved nodal groups were anterior peridiaphragmatic (100%), paracardiac (45%), internal mammary (25%), and peri-IVC (18%) nodal stations. Seven of the 11 patients (63%) had involvement of multiple lymph nodal groups. Mean longitudinal PET/CT and standalone CT followups of months showed persistence of both high-attenuation and increased uptake at these sites, without increase in nodal size suggesting metastatic disease involvement. Conclusions. FDG avid, high-attenuation lymph nodes along the lymphatic drainage pathway for parietal pleura are a relatively common finding following talc pleurodesis and should not be mistaken for nodal metastases during the evaluation of patients with history of lung cancer. 1. Introduction Since pleurodesis was first introduced in the early 19th century, it has proven to be an effective therapy for preventing recurrent pleural effusions and pneumothoraces. By far, talc pleurodesis is the most widely used method for obliterating the pleural space and is frequently performed for the palliation of lung cancer. The sequelae of talc pleurodesis in the pleura has been described in the literature and can be detected on 18F-2-fluoro-2-deoxyglucose (FDG) PET/CT imaging both by areas of high-attenuation pleural thickening and increased FDG uptake that persists over serial exams [1–5]. Once administered, talc is not confined to the pleural space. In rabbit models, talc has been shown to be absorbed through the parietal pleura into mediastinal lymph nodes and the thoracic duct, eventually entering the systemic lymphatic circulation [6]. To our knowledge, no studies have characterized the extra pleural sequelae of talc pleurodesis in humans, and more specifically, the pattern of lymph node involvement. We postulated that we would find similar features of high-attenuation and increased uptake in nodes, as found in pleura. As in pleura, talc