DNA content and cell number determination in microdissected samples of breast carcinoma in situ

Paraffin-embedded tissue (PET) is the specimen of choice for the histopathological diagnosis of cancer. PET has become a valuable resource for correlating cellular phenotype and genotype in microdissected lesions. A definitive improvement in this field has been the development of infra-red laser capture microdissection (LCM), which yields homogeneous populations of cells for DNA extraction and in vitro amplification by polymerase chain reaction (PCR). We report here a photographic and fluorescent technique for determining the number of nuclei and concentration of DNA obtained respectively by laser capture microdissection from paraffin-embedded breast cancer tissue. Breast biopsies containing carcinoma in situ were serially sectioned, mounted on plain glass slides and tumor cells were microdissected using a laser capture microscope. The DNA was extracted in digestion buffer and used directly as a template for PCR. In our protocols, each capture contained 21+/-5.4 nuclei with a DNA concentration of 115+/-5.3 pg. Also, a linear relationship was found between number of captures and DNA content (R2=0.9995). These results represent a novel contribution for a more precise correlation between phenotypic and genotypic diversity in cancer cells studied from microdissected paraffin-embedded tissue.