Role of F-18 FDG PET/CT in characterization of lesions and guiding the site of biopsy after indeterminate fine needle aspiration cytology/biopsy

Objectives Many a times in clinical practice fine needle aspiration cytology (FNAC) procedures fail to demonstrate definite diagnosis due to inadequate sampling. Moreover, the sites sampled by anatomic imaging might not be metabolically active/ uninvolved by disease process leading to decreased diagnostic yield. In this study we evaluated the role of F-18 FDG PET/CT in characterization of lesions and guiding the site of biopsy after failure of prior clinical or anatomic imaging directed FNAC/biopsy.

Methods Retrospective analysis of records of 65 patients who underwent F-18 FDG PET/CT after failed FNAC/biopsy was analyzed. Final diagnosis of the patients was made by pathological examination of site suggested site by F-18 FDG PET/CT or by correlative imaging or clinical follow up.

Results After a median follow up period of 8 months (range 6-24 months), 10 patients were diagnosed to have no disease, 3 still had inconclusive diagnosis and 52 had final definite diagnosis. F-18 FDG PET/CT findings were negative in all the 10 patients with no disease. Of the remaining 55 patients, F-18 FDG PET/CT directed biopsy could be performed in 47 patients that led to definite final diagnosis in 44 patients. In rest of the 8 patients with FDG avid disease and in whom biopsy was not performed PET/CT contributed to final diagnosis as a part of correlative imaging in 3 patients. Five patients had F-18 FDG avid disease suspicious for tubercular involvement and the patients improved with anti-tuberculosis treatment. Over all F-18 FDG PET/CT accurately suggested the biopsy site in 44/47 (93.6%) patients in whom accurate definite diagnosis could be made despite a prior failed FNAC/biopsy. Overall it contributed in accurate diagnosis in 62/65 (95.4%) patients.

Conclusions Our results suggest that F-18 FDG PET/CT can be useful as a one stop shop imaging modality to characterize the lesions and in guiding the appropriate site of biopsy in patients with prior failed FNAC/biopsy