Foreign Body Granulomatous Reaction Mimicking Tumor Recurrence After Lung Cancer Surgery: A Case Series.

Mechanical hemostatic agents, such as oxidized cellulose (Willocell©), are frequently used in thoracic surgery. Although considered safe, they can induce granulomatous reactions that mimic tumor recurrence. In this retrospective study, we analyzed patients from the Hospital Universitari de Bellvitge (July 2024-March 2025) who underwent EBUS due to lymphadenopathies with increased SUV on PET-FDG following surgery for lung cancer. Nine patients, who had undergone anatomical lung resections (VATS or RATS), presented with suspicious lymphadenopathies ipsilateral to the surgical site. EBUS-TBNA revealed no malignancy but showed amorphous material compatible with a foreign body reaction attributable to Willocell©. Only one patient was diagnosed with tumor recurrence. This case series underscores the importance of maintaining a broad differential diagnosis when evaluating potential causes of increased metabolic activity on PET/CT scans, as its specificity is limited. EBUS-TBNA proves to be a key tool for achieving an accurate diagnosis in these scenarios.