A 71-year-old man was referred for evaluation of a rectal cancer detected on colonoscopy and CT during an evaluation of hematochezia. He had a 5-year history of taking medication for underlying angina. Rectal examination showed a hard mass in the rectum. The standard laboratory tests were normal. Rectal cancer was seen as segmental and irregular wall thickening in the distal rectum with several enlarged perirectal lymph nodes on contrast-enhanced CT (Figure ​(Figure1A).1A). The soft-tissue density of the nodular mass and hazy attenuations in the jejunal mesentery (Figure ​(Figure1B)1B) were overlooked initially on either CT scans or on surgery. The patient underwent laparoscopic abdominal transanal resection and ileostomy. Adjuvant chemotherapy and ileostomy closure were performed during the year following surgery. Follow-up, contrast-enhanced CT revealed nodular jejunal and adjacent mesenteric masses in contrast to the barium-filled jejunum; the masses measured approximately 8 cm × 6 cm in width (Figure ​(Figure1C).1C). Under the suspicion of mesenteric and jejunal wall metastasis from the rectal cancer, 18F-FDG PET/CT was performed, but no remarkable FDG uptake was seen (Figure ​(Figure1D).1D). Pathological examination of a resected segment of the jejunum revealed a macroscopic, dark red, multiloculated cystic lesion measuring 8.0 cm × 5.0 cm from the mucosa to the subserosa (Figure ​(Figure1E).1E). Microscopically, it showed numerous multiloculated, cystically dilated spaces lined by attenuated endothelium and involved mucosa to subserosa. In the focal area, ectatic spaces appeared to dissect through the muscularis propria of the small intestine. Proteinaceous, fluid-containing lymphocytes seen in the cystic spaces revealed that the channel originated in the lymphatic system. The stroma was composed of a delicate meshwork of collagen punctated by lymphoid aggregates (Figure ​(Figure1F).1F). Immunohistochemical staining for CD34 showed positivity in the endothelial cells of the tumor (Figure ​(Figure1G).1G). The diagnosis of cavernous lymphangioma involving the jejunum and mesentery was established. The patient had an uneventful postoperative course and was discharged one week after surgery.

Lymphangioma or lymphangiomatosis affect the skin, the covering of various organs and areas except of the brain. About 90% are diagnosed within the first two years of their existence[^1,2]. In adults, gastrointestinal tract involvement of mesenteric lymphangioma is very rare, the distal ileal mesentery is most frequently involved[³]. The etiology of lymphangiomas is still unclear. They are considered to be a congenital dysplasia of lymphatic tissue and abnormal development of the lymphatic vessels during fetal life[^5,6]. The macroscopic appearance of lymphangioma is a cystic mass with partial septations and its histological characteristics are endothelial-lined, dilated, communicating lymphatic channels containing a variable amount of connective tissue and smooth muscle fiber[^5,7]. Lymphangiomas are generally classified as simple capillary, cavernous, and cystic according to the size of lymphatic space and the nature of the lymphatic wall[^8,9]. Cavernous lymphangioma is composed of dilated lymphatic vessels and lymphoid stroma and is connected with the adjacent normal lymphatics. Alternatively, cystic lymphangioma is composed of various-sized lymphatic spaces and has no connection with the adjacent normal lymphatics. However, as cystic lymphangiomas may have a cavernous area, clear differentiation between cystic and cavernous lymphangioma is not always possible[^9,10].