Simultaneous use of FDG-18 and ⁶⁸Ga-citrate PET/CT for the differential diagnosis of sarcoidosis and malignant disease

Abstract

A 67-year-old male presented with cutaneous rash, lassitude and fatigue of three weeks. Personal history included psoriasis and sarcoidosis. Physical examination revealed macular rash on the anterior chest wall. Laboratory results were within normal limits. Chest X-ray showed normal findings. Pulmonary function tests demonstrated a mild obstructive pattern and a mild decrease in DLCO/VA. Thorax CT revealed two nodules in the right upper and middle lobe. 68Ga-citrate PET/CT did not demonstrate any active inflammatory reaction associated with sarcoidosis while 18F-FDG PET/CT revealed increased FDG uptake in the right middle lobe, upper division bronchus and in the left lower abdominal quadrant. Histopathologic examination of the colon biopsy was compatible with adenocarcinoma and bronchoscopic biopsy of the lung lesions revealed nonspecific granulomatous inflammation. BAL cytology was normal while BAL culture did not grow any pathologic organisms. Simultaneous use of 18F-FDG and 68Ga-citrate PET/CT was the hallmark for the final diagnosis in our patient. While FDG/PET has detected the pulmonary and colonic malignant foci in our patient, 68Ga-citrate PET/CT excluded the presence of active granulomatous inflammation of sarcoidosis. Simultaneous utility of these two imaging modalities in patients with sarcoidosis is of great importance in terms of guiding the clinician towards the accurate diagnostic pathway which is the hallmark for final diagnosis, especially in the presence of concomitant malignant disease.

Keywords

• sarcoidosis
• lung cancer
• 18F-FDG PET/CT
• 68Ga-citrate PET/CT
• pulmonary metastasis