Formalin fixed paraffin embedded (FFPE) tumor samples. Microdissection is recommended for better sensitivity and specificity. This would increase the fraction of tumor cells in the sample as it allows capture of the tumor cells. The presence of normal cells that carry wild type alleles can dilute the tumor cells, and dilution by normal and inflammatory cells might impact the sensitivity of mutation detection.
In colorectal cancer DNA can be also isolated from stool samples obtained from patients with colorectal cancer.
In lung cancer, sputum can be used for isolation of DNA from cancer cells.