MICRODISSECTION AND MOLECULAR-GENETIC ANALYSIS OF HER2 NEU IN BREAST-CARCINOMA/

Precise correlation of histomorphology with molecular genetic analysis is difficult in tissues composed of heterogeneous cell populations. W e describe here a novel microdissection technique employed to correlat e HER2/neu (HER2) immunohistochemical staining with HER2 genetic analy sis in formalin-fixed, paraffin-embedded breast tissue. Fourteen invas ive ductal carcinomas were selected from the pathology files of Memori al Sloan-Kettering Cancer Center that had been immunostained for HER2. Seven tumors showed typical membrane immunoreactivity and seven were negative. A dissecting microscope was then used to isolate minute (les s than or equal to 1 mm x 1 mm) areas of invasive carcinoma and normal breast tissue for molecular study. To document the type of cell sampl e submitted for polymerase chain reaction (PCR) analysis, each microdi ssected piece of tissue was photographed prior to removal from the gla ss slide. A preliminary study of four cases compared the results of PC R and genetic analysis using microdissected hematoxylin and eosin (H & E)-stained tissue, unstained dewaxed tissue, and destained dewaxed ti ssue in four specimens. Similar results were obtained with all three t issue preparations. Thereafter, H & E stained sections were selected a s the tissue preparation of choice because tissue details were seen mo re clearly. There was complete correlation of immunohistochemical stai ning and HER2 analysis by PCR in all 14 cases. In the final 10 cases, the PCR product was resolved by gel electrophoresis and quantified by optical densitometry. Fourfold to eightfold amplification of HER2 was found in the five tumor specimens that immunohistochemically stained f or HER2. A single copy of HER2 was found in all HER2-negative tumors a nd in normal breast tissue. We conclude that it is possible to quantif y gene amplification of HER2 in minute samples of H & E-stained normal and malignant breast tissue. This microdissection technique can be ap plied to correlative histologic-molecular genetic analysis in a wide v ariety of tumor types.