The exact etiology of SIT still remains unclear, majorly caused by gene mutations and chromosomal abnormalities3, 12. As SIT itself does not seriously affect the function of organs, most patients will not have any abnormal feeling and it is generally only found during radiological examinations. However, the incidence of cardiovascular, hepatobiliary, and spleen malformations, accompanied by anomalies of abdominal vessels origination or distribution, markedly increases in SIT patients13, 14. In our case, two major anatomical malformations were presented. One malformation was the vascular variation. In regular circumstances, celiac trunk divides into common hepatic artery, splenic artery, and left gastric artery. On the contrary in this patient, the celiac trunk only divides to splenic artery and left gastric artery, while the common hepatic artery originates from the superior mesenteric artery. The other malformation was the polysplenia syndrome, where three spleens with a similar size were presented. Polysplenia syndrome is often associated with multiple visceral and vascular abnormalities15. These two malformations brought higher risks of intraoperative complications associated with incomprehension of the anatomical variations.
Notably, malignancy is also a potential outcome of SIT since the two diseases might share certain mutations in several signaling pathways. The DNAH11 (axonemal heavy chain dynein type 11) gene mutations were found to cause SIT in mice, which was further confirmed in SIT patients14. Meanwhile, the DNAH11 mutations are also associated with esophageal squamous cell carcinoma, ovarian cancer, and breast cancer16, 17. Another DNAH family member DNAH5, another SIT-related gene, was found to be mutated in several malignancies18-20. Inversin, whose mutations cause an autosomal recessive cystic disorder characterized by SIT, functions as a molecular switch between Wnt signaling pathways21, as the Wnt pathways has close relationship with carcinogenesis including development of gallbladder cancer22, 23. Therefore, it is possible that the mutations in SIT results in malignancy. However, no specific shared mutation has been verified between SIT and malignancy yet.
Previous studies have demonstrated that SIT patients might develop malignancies like esophageal cancer, pancreatic cancer, and ovarian cancer. In our case, we showed that gallbladder carcinoma, a highly malignant disease with poor prognosis24, could also be an unfortunate outcome of SIT. Specifically, our pathology diagnosis is adenosquamous carcinoma, a relatively rare type among all the pathological conditions of gallbladder malignancies25, 26, especially in a SIT setting. In comparison to adenocarcinoma, adenosquamous carcinoma is likely to have a more advanced stage with rapid progression and declined prognosis27. Optimistically, the survival data of resectable adenosquamous gallbladder cancer is comparable to gallbladder adenocarcinoma after successful radical surgical resection28, 29. Therefore, radical resection is the preferred curative approach for this patient and similar cases30, 31.
In conclusion, a SIT patient who developed a rare gallbladder adenosquamous carcinoma received a successful en-bloc surgical resection with no intraoperative vascular injuries. Proper imaging assessments, along with multidisciplinary cooperation, helps detailed evaluation of the visceral malformations, which eventually facilitates surgery success. The high-risk SIT populations should receive regular surveillance to improve early detection and long-term survival in case the malignancies occur.