C-11-methionine PET imaging of leptomeningeal metastases from primary breast cancer - a case report

Leptomeningeal metastases (LM) is often an elusive disease frequently diagn osed at an advanced clinical stage. Early diagnosis may allow for prompt in itiation of treatment with minimal tumor burden and maximal chance of survi val, especially in solid tumors such as breast cancer. Although the method of choice for imaging LM currently is by gadolinium enhanced magnetic reson ance imaging (MRI), the technique has a high sensitivity but low specificit y. We report the first case of Carbon 11-labelled methionine (Cmet) positro n emission tomography (PET) imaging of leptomeningeal metastases in a patie nt with primary breast cancer. This patient presented with clinical feature s suggestive of LM, but had inconclusive cerebrospinal fluid (CSF) findings . Although, the contrast enhanced MRI revealed calvarial and meningeal lesi ons, it is known that meningeal enhancement on MRI does not always indicate metastases. In this clinical dilemma the strong methionine uptake on PET h elped steer the diagnosis in favor of cancerous infiltration even before th e CSF cytology became positive for malignancy.