Intra-abdominal ectopic bronchogenic cyst with a mucinous neoplasm harboring a GNAS mutation: A case report

Abstract

BACKGROUND Bronchogenic cysts are congenital cysts caused by abnormal sprouting from the ventral foregut during fetal life. They usually occur in the mediastinum or lung, but there are very rare cases of ectopic bronchogenic cysts that develop in the abdominal cavity. A unique intra-abdominal ectopic bronchogenic cyst with a mucinous neoplasm that was producing carcinoembryonic antigen (CEA), harboring a GNAS mutation, is reported. The present case may contribute to clarifying the mechanism of tumorigenesis and malignant transformation of ectopic bronchogenic cysts. CASE SUMMARY In 2007, a man in his 50s was incidentally found to have an intra-abdominal cystic mass, 8 cm in diameter. Surgical resection was recommended, but he preferred to remain under observation. In 2020, his serum CEA level increased to 26.7 ng/mL, and abdominal computed tomography showed a 15 cm × 12 cm, multifocal, cystic mass located predominantly on the lesser curvature of the stomach. Since malignancy could not be ruled out, he finally underwent surgical resection. Histologically, the cystic wall was lined by ciliated columnar epithelium, accompanied by bronchial gland-like tissue, bronchial cartilage, and smooth muscle. Part of the cyst consisted of atypical columnar epithelium with an MIB-1 index of 5% and positive for CEA. Moreover, a GNAS mutation (p.R201C) was detected in the atypical epithelium, leading to a diagnosis of an ectopic bronchogenic cyst with a low-grade mucinous neoplasm. The patient is currently undergoing outpatient follow-up without recurrence. CONCLUSION An extremely rare case of an abdominal bronchogenic cyst with a low-grade mucinous neoplasm harboring a GNAS mutation was reported.

Bronchogenic cysts in rare sites (retroperitoneum, skin, spinal cord and pericardial cavity): A case series and characterization of epithelial phenotypes

“…Therefore, genetic analyses for SCN5A variants were not performed. Murakami et al ( 22 ) reported an abdominal bronchogenic cyst with a low-grade mucinous neoplasm harboring a GNAS mutation; GNAS mutation (p.R201C) in the atypical epithelium of the bronchogenic cyst indicated potential mechanism for tumorigenesis and malignant transformation. However, the present study did not find any atypical epithelium that suggested a neoplasm or malignant transformation.…”

“…None of the cases had recurrence since complete resection. Although most cases of bronchogenic cyst are asymptomatic and found incidentally during medical checkups or detailed examinations of other diseases, surgical treatment should be considered due to a risk of malignant transformation ( 2 , 22 , 23 ). The present study demonstrated that bronchogenic cysts can occur in rare sites and should be considered as a differential diagnosis before and after surgical resection to recognize a risk of malignant transformation and implement relevant management modalities such as treatment procedure and follow-up time.…”