Giant Omental Lymphangioma Presenting With Abdominal Pain and Intra-Cystic Hemorrhage in an Adult: A Case Report.

Lymphangiomas are benign tumors of lymphatic origin that usually arise in the neck and axilla during childhood; intra-abdominal involvement is rare, and an omental origin in an adult is exceptional. Because imaging features are non-specific, preoperative diagnosis is difficult, and intra-cystic hemorrhage can transform an otherwise indolent lesion into a surgical emergency. We report the case of a 46-year-old man who presented with sudden right lower-quadrant abdominal pain and a soft, mobile, tender right-abdominal mass. Contrast-enhanced computed tomography (CT) and magnetic resonance imaging (MRI) revealed a giant (approximately 25 cm), thin-walled, multilocular cystic mass containing a hematoma, with enhancement of the cyst walls but not the internal component, and feeding vessels arising from the greater omentum. Tumor markers were normal apart from mildly elevated carbohydrate antigen (CA) 125. Because malignancy could not be excluded, open resection was performed; the tumor arose from the greater omentum without invading adjacent organs and was completely excised. Histopathology confirmed an omental lymphangioma. The acute presentation was attributable to intra-cystic hemorrhage with a focal, self-sealed rupture superimposed on an indolent lesion. Because cross-sectional imaging cannot reliably distinguish lymphangioma from other cystic lesions, an immunohistochemical panel combining lymphatic and vascular endothelial markers (D2-40, CD31) with mesothelial markers (calretinin, WT-1) was decisive in excluding a mesothelial-lined cyst and mesothelioma. Omental lymphangioma should be considered in the differential diagnosis of a giant intra-abdominal multilocular cystic mass in adults, including those presenting acutely, and complete excision is both diagnostic and curative.