A case of cryptococcal pneumonia with false-positive [18F]fluoro-2-deoxy-d-glucose positron emission tomography (FDG-PET) image mimicking lung metastatic cancer

Abstract

Background

There is an increasing use of positron emission tomography with [¹⁸F]fluoro-2-deoxy-d-glucose (FDG-PET) for differential diagnosis between lung malignancy and other pulmonary diseases such as infection. However, false-positive FDG-PET images mimicking lung cancer can occur in pulmonary infection.

Objective

This study was to describe a case of cryptococcal pneumonia with false-positive FDG-PET image mimicking metastatic lung cancer.

Patient and results

We analyzed the clinical features and chest CT and FDG-PET characteristics of a case of pulmonary cryptococcosis that was initially suspected to have lung metastasis of gastric cancer and treated by surgery. During a follow-up, the 49 years old, female patient with a 7-year history of gastric adenocarcinoma showed a 1.0-cm nodule in the right lower lobe of lung on her chest CT scan with an accumulation of FDG (SUV = 4.5) on her PET image. With a clinical diagnosis of suspected lung metastatic cancer, the lung wedge resection was then performed. Histological analysis of the resected nodule confirmed a diagnosis of cryptococcal pneumonia.

Conclusion

The FDG-PET image is not particularly helpful in segregating pulmonary infection from lung malignancy in certain cases. Surgical resection is recommended for both diagnosis and treatment of pulmonary cryptococcosis.