Validity of special AT-rich sequence-binding protein 2 in distinguishing metastatic mucinous carcinomas of colorectal origin from primary ovarian mucinous carcinomas

Background Identification of ovarian mucinous carcinomas as being primary or metastatic is a problematic issue. CK7, CK20, and CDX2 are the commonly used markers in distinguishing primary ovarian mucinous carcinomas from metastatic ovarian mucinous carcinomas (MMOC). However, significant overlap in their expression was reported. Special AT-rich sequence-binding protein 2 (SATB2) has been suggested to be a diagnostic biomarker for colorectal cancer (CRC). Aim To validate the diagnostic accuracy of SATB2 in determining the metastasis of colorectal origin in ovarian mucinous carcinoma. Materials and methods Immunohistochemical expression of SATB2, CK7, CK20, and CDX2 were analyzed on 14 paraffin blocks of primary ovarian mucinous adenocarcinoma and 32 blocks of metastatic ovarian mucinous adenocarcinoma (19 colon, 9 gastric, 2 pancreas, and 2 cervix). Results SATB2 had higher specificity (100%) and accuracy (93.94%) for determining the metastasis of colorectal origin versus primary ovarian origin, compared with that of CDX2 (64.29 and 81.82%, respectively) and CK20 (50 and 72.73%, respectively). However, CDX2 had higher sensitivity (94.74%) compared with SATB2 and CK20, 89.47 and 89.47%, respectively. CK7-SATB2+ phenotype had higher specificity (100%) and diagnostic accuracy (95.65%) for the diagnosis of metastasis of colorectal origin to the ovary, compared with that of CK7-CDX2+ pattern (92.59 and 93.48%, respectively) and CK7-CK20+ pattern (92.59 and 89.13%, respectively). Furthermore, adding SATB2 to previous panels CK7-CDX2+ or CK7-CK20+ increases their specificity to 100% for the diagnosis of metastasis of colorectal origin to the ovary. Conclusion SATB2 has more specificity and diagnostic accuracy than CDX2 and CK20 for the diagnosis of metastatic mucinous CRC. SATB2 in combination with CDX2 or CK20 increases their specificity and accuracy for differentiating metastatic mucinous CRC from primary ovarian mucinous carcinoma.