Construction and validation of tissue microarrays of ductal carcinoma in situ and terminal duct lobular units associated with invasive breast carcinoma.

Construction of tissue microarrays (TMAs) to efficiently characterize large sets of noninvasive epithelial lesions in the breast by immunohistochemistry is an appealing investigative approach, but presents technical challenges. We report methodologic studies performed to optimize methods for building TMAs from noninvasive breast tissues collected in a large case-control study of breast cancer. Using a manual arraying technique with 2.0-mm diameter needles, we constructed TMAs from specimens obtained from 32 women with breast cancer containing the following targets: (1) 28 terminal duct lobular units (TDLUs); (2) 28 ductal carcinomas in situ, and (3) 23 invasive carcinomas. Using careful target selection, we achieved representation of approximately 80% of noninvasive targets with sustained preservation through section 30 of the TMAs. Immunohistochemical staining of TDLU targets demonstrated positive staining for estrogen receptor (ER) in 30.8% of tubules and for progesterone receptor (PR) in 50.0%. To establish an efficient method to evaluate staining results in TDLUs, we created a categorical scoring system to approximate the percentage of tubules containing positive stained cells (<10%, 10% to 50%, >or=50%), and compared the results with those obtained by tubule counting. Comparison between the two methods demonstrated exact agreement for 70.8% of ER and 79.2% of PR stains without two-category discrepancies. ER/PR expression levels in multiple (up to 4) noninvasive targets of the same tissue type (TDLU or DCIS) from a single block showed good correlation. These data suggest that it is feasible to produce TMAs of noninvasive breast structures, albeit with careful selection of targets, and that immunostains of such cores may permit efficient immunohistochemical characterization of peritumoral tissues. Additional exploration of this approach is needed.