An approach to interpreting immunohistochemical stains of adenocarcinoma in small needle core biopsy specimens: the impact of limited specimen size.

Interpreting immunohistochemical stains of metastatic adenocarcinoma in small needle core biopsy specimens is not always straightforward. We studied the effects of small specimen size on immunohistochemical stain results in 20 colorectal adenocarcinoma hepatic resection specimens stained with cytokeratin (CK)7 and CK20. We superimposed 18- and 20-gauge needle core biopsy computer images. The results in needle core biopsy specimens correlated best with resection specimen results when immunoreactivity was assessed using the 3 images with the highest percentage of immunoreactive cells. CK7- and CK20+ needle core biopsy specimens correlated best when a higher percentage cut point was used. Immunohistochemical stains in small needle core biopsy specimens should be based on the regional area with the greatest immunoreactivity. The positive result cut point should increase as the amount of stainable carcinoma available for interpretation decreases.