Spontaneous rupture of a mucinous cystic neoplasm of the liver resulting in a huge biloma in a pregnant woman: A case report

BACKGROUND: Mucinous cystic neoplasm of the liver (MCN-L) and intraductal papillary neoplasm of the bile duct (IPN-B) are two different types of mucin-producing bile duct tumour that may complicate the course of pregnancy. To the best of our knowledge, we describe herein the first case of MCN-L with spontaneous rupture during pregnancy necessitating complex surgical treatment. CASE SUMMARY: A 24-year-old woman was initially admitted to another hospital in October 2018 with signs of jaundice (serum bilirubin level 12 mg/dL) and upper abdominal pain radiating to the left shoulder. Initial magnetic resonance imaging (MRI) of the abdominal cavity revealed a multilocular cystic tumour of the liver hilum (37 mm × 40 mm in diameter) located between segments 3 and 4 of the left liver lobe. Six weeks later (December 2018), the patient was found to be 12 wk pregnant and was referred to our institution for further diagnostics and treatment. At admission, a soft, palpable, and tender mass in the left upper abdomen was found. It was determined via MRI (with no intravenous contrast in view of the first-trimester pregnancy) to be a large collection of fluid (19 cm × 17 cm × 10 cm) located close to the liver hilum and below the left liver lobe. The patient did not undergo any diagnostic or therapeutic procedures nor did they have any abdominal trauma in the preceding weeks. The fluid collection proved to be of biliary origin following percutaneous drainage. Therefore, we concluded this was a spontaneous rupture of an MCN-L with the formation of a biloma. The MRI study also revealed the previously found cystic tumour of the liver hilum communicating with the left hepatic duct, which, together with left hepatic duct dilatation, suggested the diagnosis of IPN-B. The follow-up MRI with intravenous gadolinium contrast performed in the second trimester of pregnancy (week 14) showed, in turn, some features of MCN-L, including enhancement of the internal septations within the cystic liver mass. A precise preoperative differential diagnosis between IPN-B and MCN-L was therefore not possible. The patient was submitted to surgery in the second trimester of pregnancy (week 18). Surgery included a cholecystectomy, left hepatectomy, and concomitant resection of the extrahepatic bile ducts followed by anastomosis of the right hepatic duct with the Roux limb of the jejunum. The post-operative period was uneventful and the patient was discharged 8 days after surgery. The histopathological examination of the resected specimen revealed a final diagnosis of MCN-L with low-grade dysplasia and epithelium surrounded by ovarian-type stromal tissue. The patient delivered a healthy baby girl and both remain well at present, after 2 years of follow-up since surgery. CONCLUSION: The differential diagnosis and management of MCN-L and IPN-B may be very challenging, particularly in the setting of pregnancy. When indications for surgery are obvious, the final diagnosis is based on histopathological examination, with ovarian-type stroma being pathognomonic for MCN-L. We believe that the growth of this subepithelial stroma secondary to the high levels of sex hormones produced during pregnancy might have been the main causative factor leading to the tumour rupture with the formation of a biloma in our patient.