Appendiceal mucocele: A diagnostic dilemma in differentiating malignant from benign lesions with CT

The purpose of this study was to assess the feasibility of using CT to differentiate malignant from benign lesions in patients with pathologically confirmed appendiceal mucoceles.

CT scans of 18 consecutively registered patients (11 men, seven women; age range, 21-78 years) with pathologically confirmed appendiceal mucocele were reviewed retrospectively. Patients were classified into three groups according to pathologic results: nonneoplastic mucocele (n = 3), mucinous cystadenoma (n = 10), and mucinous cystadenocarcinoma (n = 5). The nonneoplastic and mucinous cystadenoma groups were formed into a benign group, and the mucinous cystadenocarcinoma constituted the malignant group. Two experienced radiologists working in consensus assessed the shape, short diameter, density, contour, and wall thickness of the masses. The presence of calcifications, internal septations, soft-tissue thickening, periappendiceal fat stranding, intraperitoneal free fluid and pseudomyxoma peritonei were also evaluated. The CT results were compared for malignant and benign appendiceal mucoceles.

CT showed statistically significant differences in wall irregularity and soft-tissue thickening between malignant and benign cases (p < 0.05). Short diameter of mucoceles, attenuation of intraluminal contents, maximal wall thickness, calcifications, internal septations, periappendiceal fat stranding, intraperitoneal free fluid, and pseudomyxoma peritonei in the lesions did not differ significantly between the benign and malignant groups (p > 0.05).

Differentiating malignant from benign mucoceles can be difficult with CT. Irregular walls and soft-tissue thickening are features most likely to be associated with malignancy.