Imaging features of glucagonoma syndrome: A case report and review of the literature

Glucagonoma syndrome appears as an extremely rare neuroendocrine tumour, with few studies ever having detailed its imaging manifestations. In particular, the magnetic resonance imaging (MRI) features of the lesion have not yet been reported. The present study describes a 54-year-old male who presented with uncontrollable skin erythema and weight loss that had been apparent for two years, and diabetes mellitus that had been apparent for five years. The glucagon level was 180 pg/ml. The plain abdominal computed tomography (CT) scan revealed a solid tumour in the neck of the pancreas, which was slightly reinforced during the arterial phase of the enhanced CT scan. Upon MRI, the lesion exhibited a low signal on T1-weighted imaging, and a slightly high signal on T2-weighted and half-Fourier acquisition single-shot turbo spin echo sequence imaging, which measured ~4.5×3.0×3.0 cm in size. Upon diffusion-weighted imaging, the lesion demonstrated heterogeneous hyperintensity, which was mildly enhanced during the arterial phase and washed out during the portal venous phase of gadopentetate dimeglumine-enhanced MRI. (18)F-fludeoxyglucose ((18)F-FDG) positron emission tomography (PET)-CT identified a mild uptake of (18)F-FDG by the lesion. The patient was diagnosed with glucagonoma syndrome, and a distal pancreatectomy and splenectomy were subsequently performed. Microscopy revealed that the tumour cells exhibited nest- and belt-like arrangements. The immunohistochemical staining identified positive reactions for glucagon, synaptophysin and chromogranin A, which are consistent with a diagnosis of glucagonoma. Following surgery, the symptoms disappeared and the glucagon level returned to normal. In conclusion, imaging examinations are useful for determining the location and size of a glucagonoma. In particular, MRI is able to identify the distinctive morphological features of the lesion. Immunohistochemical staining provides diagnostic evidence based upon the neuroendocrine features.