Giant mucinous cystic neoplasm of the liver in a young asymptomatic woman: A case report

RATIONALE: Mucinous cystic neoplasm of the liver (MCN-L) is an uncommon cystic tumor with low malignant potential that mainly occurs in women. Because many patients have few or no symptoms and imaging findings may look similar to simple liver cysts or other cystic lesions, it is easy to make an incorrect diagnosis before surgery. PATIENT CONCERNS: A 36-year-old woman had no discomfort. A large cystic liver lesion was found by chance during a routine health checkup. She did not report abdominal pain, distension, fever, jaundice, or weight loss. DIAGNOSES: Imaging examinations showed a giant multilocular cystic mass about 20 cm in size in segment IV of the liver, with septal enhancement. Serum carbohydrate antigen 19-9 (CA19-9) was markedly increased (553 IU/mL), while other tests were unremarkable. MCN-L was suspected. Histopathology of the resected specimen confirmed a low-grade MCN-L with ovarian-type stroma, and immunohistochemistry showed estrogen and progesterone receptor positivity in the stromal cells. INTERVENTIONS: Because the tumor was very large and located close to major hepatic vessels, the patient underwent open segment IV hepatectomy. The whole cystic lesion was removed en bloc without rupture. OUTCOMES: The postoperative recovery was smooth, without bleeding, bile leakage, or infection. During 24 months of follow-up, abdominal computed tomography and serum CA19-9 were checked every 6 months. No tumor recurrence or metastasis was observed, and CA19-9 returned to the normal range. The patient's quality of life remained good. LESSONS: When a very large hepatic cystic lesion is identified in a young woman, especially with elevated CA19-9 and septal enhancement on magnetic resonance imaging, MCN-L should be considered in the differential diagnosis. Because preoperative diagnosis can be difficult, careful assessment of lesion size, internal architecture, and its relationship to major vessels is essential. Complete surgical resection with negative margins remains the preferred treatment, as it reduces the risks of recurrence and malignant transformation.