Rationale: Mucinous cystic neoplasms (MCNs) are relatively rare lesions, accounting for 2%-5% of all exocrine pancreatic neoplasms. MCNs mainly occur in women (female:male ratio = 20:1), with a peak incidence in the 5th decade of life. Osteoclast-like giant cell tumors (OGCTs) are rare and relatively aggressive neoplasms, comprising <1% of all pancreatic carcinomas. Herein, we present a rare "combination tumor" case and discuss the impact of mural nodules in pancreatic MCNs considering malignant transformation.
Patient concerns: A 54-year-old Mongolian man, without vomiting, nausea or jaundice, presented with abdominal distention since 3 months. He had a 7-year history of diabetes. Physical examinations indicated slight middle abdominal tenderness without rebound tenderness or rigidity. Laboratory results revealed that the level of carcinoembryonic antigen (CEA) was 1.16 ng/ml (normal: <5 ng/ml); CA-199: 30.02 U/ml (normal: <27 U/ml); hemoglobin: 143 g/L; fasting glucose: 7.71 mmol/L; and albumin: 43 g/L. Abdominal enhanced computed tomography revealed a 7 × 6 cm solid neoplasm in the pancreatic body with partial enhancement and heterogeneity. Endoscopic ultrasound revealed a solid-cystic space-occupying lesion in the pancreatic body.
Diagnosis: The preoperative preliminary diagnosis was pancreatic solid-cystic tumor, possibly a solid pseudopapillary tumor. Postoperative pathological findings revealed a pancreatic borderline MCN with an OGCT embedded in a mural nodule of the capsule. Immunohistochemical results indicated a simultaneous dual origin from the epithelium and stroma.
Interventions: The patient underwent open distal pancreatectomy and splenectomy. Postoperative blood glucose levels were closely monitored and regulated. We intravenously administered single-agent gemcitabine (1400 mg on day 1) as the first-time chemotherapy, 1 month after surgery. After the first chemotherapy, the patient refused to receive further treatment owing to personal reasons.
Outcomes: The patient showed uneventful recovery and was discharged 13 days after the initial surgery. Follow-up was performed 1, 3 and 6 months after surgery. At 6 months, abdominal computed tomography scan showed no signs of recurrence, regional lymphadenopathy, or other abnormalities. And laboratory tests showed a platelet count of 301 × 10/L, postprandial blood glucose of 12.9 mmol/L and CA-199 level of 20 U/ml. The patient had no obvious discomfort.
Lessons: Although pancreatic MCNs are widely accepted as borderline tumors, malignant transformations may occur due to various risk factors (cyst size, mural nodules, septations, and tumor location). The combination tumor in this case was more likely to increase the possibility of malignant biological behavior, thereby worsening overall prognosis. Therefore, long-term follow-up must be maintained with strict monitoring.