For centuries pathologists have relied on the microscopic examination of tumors to distinguish between atypical moles and melanoma. By analyzing the level of proteins within mole cells, mass spectrometry can aid in the diagnosis of atypical moles. In this study, mass spectrometry correlated better than the gold standard of histologic examination to determine if an atypical mole was in fact benign or a melanoma. Early diagnosis of melanoma is critical to cure and long term survival.