It was fortunate for the middle-aged woman that she presented her symptoms at the European Institute of Oncology (IEO), where doctors had seen another strange case just two years before.

The 59-year-old woman had complained of chest pain and shortness of breath. A biopsy revealed that she had an unusual type of "heart cancer" called cardiac lymphoma.

But a week after receiving treatment, the patient developed a headache and her motor skills began to deteriorate.

Coincidentally, in 2011, a similar case had presented at the IEO. In that instance, the patient's cardiac lymphoma had unexpectedly relapsed to the brain.

Remembering this odd case, doctors were able to diagnose the second woman with the same condition.

A case report published in ecancermedicalscience describes both of these unusual cases and offers recommendations for diagnosing similar occurrences.

Cardiac lymphoma is a rare condition, and doctors often overlook the potential of metastasis to the central nervous system, says Dr Niccolo Frungillo of the IEO, corresponding author of the study.

"In my opinion it is very important to identify prognostic factors that predict the brain relapse of lymphoma," says Dr Frungillo. "It's a rare - but often fatal - complication."