# Nocardia masquerading as pulmonary malignancy in a patient with adult-onset immunodeficiency on 18F-FDG PET/CT

## TL;DR

An elderly man with a history of cancer had a lung lesion that looked like cancer on a PET scan but was actually a rare bacterial infection called Nocardia.

## Contribution

This case highlights the diagnostic challenge of Nocardia infection mimicking lung cancer on 18F-FDG PET/CT.

## Key findings

- The PET/CT showed a spiculated lung lesion and lymph node involvement suggestive of malignancy.
- Microbiology confirmed Nocardia Beijingensis as the cause of a disseminated infection.
- The patient also developed brain abnormalities consistent with central nervous system involvement.

## Abstract

A 77-year-old man with a history of left nephrectomy for renal cell carcinoma and partial hepatectomy for cholangiocarcinoma underwent 18F-FDG PET/CT for assessment of an irregular lung lesion. FDG-PET demonstrated development of an intensely avid spiculated left lower lobe pulmonary lesion and intensely avid left pulmonary hilar nodes, raising suspicion for a malignancy. Eleven days following the PET study, the patient was admitted to hospital with an altered mental state. CT brain revealed diffuse round hyperdensities within the brain parenchyma. Microbiology of the lung lesion was positive for Nocardia Beijingensis and he was subsequently diagnosed with disseminated nocardiosis.