Dermoid cyst of the greater omentum: rare and innocent?

To cite: Schols RM, Stassen LP, Keymeulen KB, et al. BMJ Case Rep Published online: [please include Day Month Year] doi:10.1136/bcr-2012008304 DESCRIPTION An 83-year-old woman presented with decreased appetite and weight loss. Upon physical examination a palpable swelling in the lower abdomen was detected. The radiologist was consulted regarding the possible presence of a malignancy. A CT showed a bilobar mass located centrally in the pelvis, consisting of a cystic and solid component with a peel-shaped calcification and a maximum diameter of 9.2 cm (see figure 1). Differential diagnosis: a degenerative leiomyoma of the uterus or a dermoid cyst of the right adnexa, presumably corresponding to the findings of the physical examination. Furthermore, CT revealed an obstructing tumour in the transverse colon located at the splenic flexure. Biopsy during colonoscopy revealed an intramucosal adenocarcinoma 55 cm ab ano, with focal suspected invasive growth. It was decided to perform a transverse colectomy. Right at the beginning of the surgery a 10 cm large calcified sphere was found connected to the greater omentum and was resected (see figure 2). Histological examination of the excised tissue from the omentum revealed a cyst of 179.5 g and dimensions of 9.5×6×5.5 cm, with a fibrous wall filled with an amorphous material, calcification and hair. The pathologist’s conclusion was the diagnosis of a rare dermoid cyst of the greater omentum; there were no signs of malignancy. Dermoid cysts (mature cystic teratomas) of the omentum rarely occur. Usually these arise in the ovary. The diagnosis can be achieved by ultrasound and on CT. The exact localisation of the tumour is however extremely difficult. Potential malignant degeneration has to be considered, but is infrequent. Resection is the treatment of choice. Nevertheless, advanced age of the patient, absence of symptoms and a very low risk of malignant degeneration can be reasons for not performing surgery.