The Role of SATB2 as a Diagnostic Marker of Sinonasal Intestinal-type Adenocarcinoma.

Background: Intestinal-type adenocarcinoma (ITAC) of the nasal cavity and paranasal sinuses is an uncommon tumor associated with exposure to wood and leather dust, nickel, and possibly smoking. ITAC shares phenotypical features with colorectal carcinoma. In contrast to most non-intestinal-type sinonasal adenocarcinomas, ITAC is an aggressive adenocarcinoma with poor clinical outcome; therefore, its reliable separation from non-ITAC is very important.

Aim: The use of a combination of immunohistochemical markers of intestinal differentiation was tested in a cohort of sinonasal carcinomas of different types. The aim of this study was to explore a new intestinal marker, SATB2, in conjunction with CDX2 and CK20 in differential diagnosis of sinonasal adenocarcinomas.

Materials And Methods: Seven ITACs, 66 non-ITACs, and 1 case of extensive intestinal metaplasia (IM) of the nasal mucosa were included in the study and stained with SATB2, CK20, CDX2, and CK7 antibodies. Detection of mismatch repair proteins was performed in all cases of ITAC. All 7 sinonasal ITACs have been tested for KRAS, NRAS, and BRAF gene mutations.

Results: All ITACs showed positive expression for SATB2, whereas all non-ITAC cases were negative. The only 1 case of IM was found to be positive for SATB2, whereas the same case showed negative expression of CK20 and only focal immunostaining for CDX2. The genetic analysis showed that only 1 sinonasal ITAC (1/7) showed KRAS c.35G>C, p.(Gly12Ala) mutation, whereas BRAF and NRAS genes were wild type. Four ITACs revealed wild-type KRAS, NRAS, and BRAF, and 2 remaining cases were not analyzable. All ITACs showed preserved nuclear expression of mismatch repair proteins.

Conclusions: SATB2 in combination with CDX2 and CK20 differentiates sinonasal ITAC from non-ITAC with increased diagnostic sensitivity and specificity and detects IM in the sinonasal tract more easily.