A 31 yr old male† presented to the Infectious Diseases Department of Yichang Central People’s Hospital, Hubei province, P.R. China, in June 2017, with a fever of unknown origin for over three weeks. The positive laboratory results mainly included erythrocytopenia (3.62×1012/l; normal range: 4.3-5.8), leukopenia (3.21×109/l; normal range: 3.5-9.5), thrombocytopenia (118×109/l; normal range: 125-350) and a marked increase in the level of lactate dehydrogenase (1208 IU/l; normal range: 120-250).
However, imaging examinations, including non-enhanced chest and abdominal computed tomography (CT) and abdominal ultrasound were unremarkable (Fig. 1). A whole-body 18Fluorine labelled fluorodeoxyglucose positron-emission computed tomography/CT (18F-FDG PET/CT) was done to look for occult infection or malignancy. PET/CT images (Fig. 2) showed abnormally elevated FDG uptake in bilateral kidneys and humerus, left femoral neck and retroperitoneal lymph nodes (all <1 cm in diameter) with a maximum standardized uptake value (SUVmax) of 18.1. No obvious morphological abnormalities were observed in these hypermetabolic lesions on non-enhanced CT. Subsequently, non-Hodgkin’s cytotoxic T-cell lymphoma was confirmed by immunohistochemistry (Fig. 3) through left femoral neck puncture biopsy under the guidance of PET/CT and the patient was transferred from the infectious diseases to the haematology department for treatment. After two cycles of chemotherapy, a repeat PET/CT revealed that the metabolic activity returned to the normal level with a SUVmax of 3.0 (Fig. 4).
Lymphoma can involve a variety of tissues and organs outside the lymph nodes. When there is no obvious morphological abnormality, traditional imaging may not pick up abnormal lesions. However, an 18F-FDG PET/CT can be invaluable in diagnosing an occult malignancy and for subsequent evaluation for the remission of disease.
Acknowledgment: The authors would like to thank pathology expert Yu-fei Liu, haematology expert Jing-ming Guo and oncology expert Xin-hua Xu, The First Clinical Medical College of Three Gorges University, Yichang, China, for providing professional advice.
Conflicts of Interest: None.