Background: Lymphangioma (LA) is a benign tumor that predominantly occurs in children, and is characterized by abnormal proliferation of lymphatic vessels. It is commonly present in areas such as the head, neck, and axilla. Mesenteric cystic lymphangioma (MCL) is relatively rare in adults. We reported a case of an elderly patient with a massive cystic LA of the mesentery that exerted pressure on surrounding tissues, resulting in both local and systemic symptoms.

Methods: The patient is a 66-year-old male who presented to our hospital with a history of recurrent abdominal pain of unknown origin for over 20 years. In the past month, the abdominal pain has worsened and is accompanied by abdominal distension. Methods: Abdominal computed tomography angiography revealed a large cystic low-density mass in the right middle and lower abdomen, measuring approximately 14.9 cm × 12.8 cm × 14.9 cm. The mass contained septations, with mild enhancement of the cyst wall and septa on contrast-enhanced imaging. Small blood vessels, originating from the superior mesenteric artery, were seen traversing the lesion. Abdominal enhanced magnetic resonance imaging demonstrated a large cystic mass in the right lower abdomen, measuring approximately 17.2 cm × 14.5 cm × 8.1 cm. The mass exerted pressure on the adjacent bowel and bladder, with poorly defined borders between the lesion and the adjacent bowel. Methods: Surgical intervention was undertaken to alleviate the patient's symptoms and get a definitive diagnosis. The postoperative pathological results confirmed the diagnosis of cystic LA of the mesentery of the small intestine.

Results: The patient resumed oral intake on the third day following surgery and was discharged in stable condition on the sixth day following surgery. The patient was followed up for 1 month postoperatively without signs of recurrence.

Conclusions: MCL is a rare entity often presenting with nonspecific early symptoms. As the disease progresses, patients may experience abdominal pain, distension, and other gastrointestinal manifestations, potentially culminating in acute abdominal emergencies. While definitive diagnosis necessitates postoperative histopathology, preoperative imaging plays a crucial role in diagnosis. Therefore, clinicians should consider MCL in the differential diagnosis of unexplained abdominal masses.