Mycobacterium infection as a mimicker of brain metastasis.

Mycobacterium infection is a differential diagnosis to be considered in brain multifocal lesions with peripheral enhancement.

A 52‐year‐old Caucasian man presented with headache, progressive left eye sight impairment and 18 Kg weight loss in 5 months.

Brain computed tomography (CT) and brain magnetic resonance imaging (MRI) are demonstrated (Figure 1A,B).

FIGURE 1

A, Axial brain computed tomography (CT) with contrast showing multiple ring‐enhancing lesions with perilesional edema and mass effect in the left cerebellar hemisphere (white arrow). B, Axial brain magnetic resonance imaging (MRI) with a heterogeneous lesion in the left frontal lobe with hypointensity on T2‐weighted image (white arrow). C, Brain histology with hematoxylin and eosin staining, 400× magnification, showed epithelioid histiocytes (black arrowheads). D‐ Ziehl‐Neelsen staining, 1000× magnification, revealed scattered bacilli (black arrow)

A chest CT showed mediastinal lymph node enlargements, without parenchymal lesions. Cerebral spinal fluid analysis and cultures showed no abnormalities.

Biopsy showed a granulomatous lesion with detection of acid‐alcohol resistant bacilli (Figure 1C,D).

The patient received treatment for quaternary tuberculosis, with significant clinical improvement.

Multifocal lesions with peripheral enhancement (ring‐enhancing pattern) can be a diagnostic challenge. Even advanced sequences, such as perfusion, can be confusing, as mycobacterium infection lesions can show hyperperfusion, which is most typically seen in multiple metastatic lesions.

Cerebrospinal fluid (CSF) findings could be unremarkable or demonstrate a nonspecific increase in protein. CSF culture is usually negative and the diagnosis usually depends of neuroimaging findings, protein‐purified derivative reactivity, and response to antituberculous therapy.

Early recognition on the imaging and treatment of this condition plays an important role in patient morbidity and mortality.

Biopsy is still the main tool for the definitive diagnosis.

Mycobacterium infection is a differential diagnosis to be considered in multifocal ring‐enhancing lesions.

CONFLICT OF INTEREST

The authors declare no competing interest.

AUTHOR CONTRIBUTIONS

GSOW: drafting the article and final revising. GRA‐M: histological evaluation and final revising. LSQ: histological evaluation and final revising. FR: conceived of the presented idea; neuroimaging evaluation; and drafting the article and final revising. All authors contributed to the final manuscript.

ETHICAL APPROVAL

This study was approved by our Institutional Ethics Committee (CAE number 36223320.7.0000.5404).