Not all enhancing lesions are tumor recurrence: Foreign body granulomas after glioma resection

Postoperative imaging surveillance is essential in the management of glioma patients. However, new or progressive contrast-enhancing lesions do not always indicate true tumor recurrence. Foreign body granulomas (FBG), also known as textilomas, may arise as inflammatory reactions to hemostatic or sealing materials used during surgery and can closely mimic tumor progression on MRI. Distinguishing between these entities remains a major diagnostic challenge with important therapeutic implications.

We retrospectively analyzed glioma re-operations performed for suspected recurrence at a tertiary neurosurgical center between 2016 and 2020. Demographic data, tumor histology, intraoperative foreign material, adjuvant therapy, and time to re-operation were assessed. Histological findings were classified as recurrence or no tumor. Preoperative MRI was reviewed according to RANO criteria, with emphasis on diffusion-weighted imaging and apparent diffusion coefficient (ADC) values. Univariate analyses were conducted.

Of 211 glioma patients, 38 (18 %) underwent re-operation for suspected recurrence. Histological recurrence was confirmed in 27 cases (71.1 %), while 11 (28.9 %) showed no tumor. Foreign material was identified in three non-tumor cases; the remaining showed post-inflammatory or unclear changes. All non-tumor cases had been radiologically classified as progressive disease. ADC values tended to be lower in the non-tumor group, suggesting diffusion restriction, but without statistical significance. Oxidized cellulose was frequently used in both groups.

FBG are a relevant and likely underrecognized differential diagnosis in suspected glioma recurrence. Conventional MRI and RANO criteria alone may be insufficient. Diffusion-weighted imaging may provide additional clues but is not definitive. Increased awareness and multidisciplinary evaluation are essential to avoid unnecessary interventions and overtreatment.