N-acetylaspartate-Like Peak on MR Spectroscopy – A Useful Clue For Brain Metastases that Originate from Mucin- Expressing Primary?

Differential diagnosis between high-grade glioma and solitary cerebral metastasis remains to be diagnositc challenge using conventional imaging techniques. Magnetic resonance spectroscopy (MRS) is an advanced clinical magnetic resonance imaging technique that might help in resolivng this dillemma. Here we present a pictorial case series of 5 patients with observed peak close to the resonance of N-acetyl aspartate in the secondary tumors of various origin, potentially associted with the expression of mucin. Two patients had melanoma metastasis, one non-small-cell lung cancer metastasis, one metastasis from oropharyngeal cancer and one from the breast cancer. In all patients contrast-enhanced magnetic resonance imaging of the brain showed solitary infiltrative lesion. MRS was performed in all lesions, and showed dominant peak close to 2.0ppm, and was reported as “N-acetyl-aspartate-like”. Based on the existing knowledge, this peak probably represents N-acetyl glycoproteins, as a reflection of mucin expression on the cancer cells. Thus, this dominant peak might be a very useful clue for attributing the single ring-enhancing lesions to the secondary dissemination of a mucin-expressing producing primary cancers, including melanoma, breast cancer, non-small cell lung cancers and oropharyngeal carcinoma, rather than to a high-grade glioma.