English: (Text from Cancer.gov)

Scientists have learned that it is not necessary to identify every protein active in cancer and captured by laser microdissection. To accomplish a molecular diagnosis, all that may be needed is to separate and preserve a unique subset, a pattern of proteins shared by all patients with the same cancer type.

For example, researchers collected blood samples from a group of patients with diagnosed ovarian cancer. They used mass spectrometry to collect all the protein profiles that appeared in the patients' serum samples. While there was some variation from patient to patient, pooling enough samples of confirmed ovarian cancer enabled clinicians to use cluster analysis to determine what subset of proteins consistently served as markers for the presence of cancer. Identification of this subset was successful, and today we are on our way to completing a method of molecular diagnosis for ovarian cancer.