Dual Stain With SATB2 and CK20/Villin Is Useful to Distinguish Colorectal Carcinomas From Other Tumors.

Objectives: Small sample size limits the number of immunostains that may be attempted in colorectal carcinoma (CRC) biopsy specimens. We investigated the utility of dual stain with special AT-rich sequence binding protein 2 (SATB2) or caudal-type homeobox 2 (CDX2) and cytokeratin 20 (CK20) or villin in identifying CRC.

Methods: Tissue microarrays with 222 CRCs and 375 other carcinomas were built. Dual stain was performed pairing nuclear stains CDX2 or SATB2 with CK20 or villin.

Results: All four single stains showed excellent sensitivity (93%-99%) but variable specificity (56%-88%) for CRC. All four dual stains also showed excellent sensitivity (90%-96%) while much improved specificity (88%-98%) compared with single stains. SATB2 dual stain (with CK20 or villin) showed a higher specificity than CDX2 dual stain (with CK20 or villin) with a comparable sensitivity.

Conclusions: SATB2 dual stain shows the greatest potential clinical utility in identifying CRC and is superior to CDX2 dual stain. More important, SATB2 dual stain could be helpful for specimens with limited tissues or those having a nonclassic staining pattern.