Parovarian cystadenoma: sonographic features associated with magnetic resonance and histopathologic findings.

Differentiation between malignant and benign parovarian tumors is necessary before any surgery is planned, because the postoperative spread of ovarian cancers is well documented. Both malignant and benign parovarian tumors may contain intracystic projections, so their presence is not a differentiating factor. We describe the cases of 2 patients with parovarian cystadenomas that were evaluated using sonography, MRI, and histopathology in an attempt to begin to identify the sonographic characteristics of such lesions and correlate them with MRI and histopathologic findings. In both cases, sonography revealed a cystic mass that contained multiple small intracystic mural nodules, most of which were associated with the "Chinese hat" artifact. MRI findings confirmed the presence of the cystic masses and the nodules. Histopathologic findings confirmed the diagnosis of serous cystadenoma arising in a parovarian cyst; the intracystic nodules consisted of fibrotic tissue covered with a single layer of epithelium. Thus, the results of all 3 evaluations correlated well. This characteristic sonographic appearance may be useful in making an accurate preoperative diagnosis of parovarian cystadenomas.