[Extra-organic primary tumor in pelvis: correlation of multi-detector row computed tomography, anatomy and pathology]

The purpose of this study was to investigate the correlation between multi-detector row CT (MDCT) features, pathological findings and the anatomic basis of extra-organic primary tumors in pelvis so as to improve the document diagnosis of these entities. We retrospectively analyzed the MDCT manifestations of 20 cases with surgically and/or pathologically evidenced diagnoses of extra-organic primary tumors in pelvis. The results showed that, in 14 cases, the tumors were located in the pelvis, and 6 of them involved both pelvis and hypogastric zone. There were 8 tumors located in the peritoneal cavity of the pelvis, and 3 of them also involved the extraperitoneal space of the pelvis. In the peritoneal cavity, 2 tumors of male patients were located in the rectovesical pouch while 3 tumors of female patients were located in the rectouterine pouch. The majority of entities in these 2 pouches were germ cell tumors (3/5 cases, 60.0%). In the extraperitoneal space, 5 of 12 tumors were located in the pararectal space and 5 of them were located in the retrorectal space. The majority entities of these 10 cases were germ cell tumors (7/10 cases, 70.0%). Lymphoma mainly involved paravesical and pararectal space in disorder. Calcification occurred in 6 cases, including 4 cases of teratoma, 1 case of neurilemmoma, and 1 case of malignant teratoma. The fatty element occurred in 7 masses, including 4 cases of teratoma, 1 case of malignant teratoma, 1 case of mixed germ cell tumor, and 1 case of liposarcoma. MDCT with multi-planar reconstruction (MPR) could more clearly reveal the anatomic location of the extra-organic primary tumor in pelvis, could unveil the tumor's relationship with its surrounding organs, and could help to differentiate benign tumors from malignant tumors.