Dumbbell scoring system a new method for the differential diagnosis of malignant and benign spinal dumbbell tumors

Study Design. Retrospective diagnostic analysis. Objective. The aim of the study was to establish a new scoring system, the dumbbell scoring system (DSS), for preoperative evaluation of the malignant potential of spinal dumbbell tumors (SDTs). Summary of Background Data. Among SDTs, benign tumors such as schwannomas occur frequently, whereas malignant SDTs, including malignant peripheral nerve sheath tumors, are uncommon. No scoring system has been developed to preoperatively diagnose the malignant potential of SDTs. Methods. We retrospectively reviewed the records of 59 consecutive patients with SDTs. The following imaging features were recorded: tumor size, tumor shape, tumor boundary, pattern of enhancement of intratumoral lesions (homogeneous or heterogeneous), cyst formation in the tumors on magnetic resonance imaging, and enlargement of neural foramina and scalloping or osteolytic destruction of surrounding bones on computed tomography. The prevalence of characteristic imaging features in malignant and benign SDTs were evaluated, and appropriate cut-off points for the DSS score were obtained using receiver operating characteristics. Results. Twenty cases were confirmed to be malignant tumors. Pathological diagnoses of the malignant SDTs were as follows: 11 cases of malignant peripheral nerve sheath tumor; 3 cases of malignant lymphoma; and 1 case each of extraskeletal Ewing sarcoma, hemangiopericytoma, hemangioendothelioma, malignant myoepithelioma, neuroblastoma, and plasmacytoma. The DSS was based on four characteristic imaging features confirmed as significant predictors of malignant SDTs, namely, maximal diameter greater than 5 cm, irregularly lobulated tumor, tumor boundary indistinguishable from surrounding tissues, and osteolytic bone destruction. Malignant SDTs showed a higher DSS score (median 5.5 points) than did benign SDTs (median 0 point). The optimum cut-off value for the DSS score was 3 points, and the sensitivity and specificity for the diagnosis of malignant SDTs were 90% and 84.6%, respectively. Conclusion. This scoring system may be helpful for preoperative decision making. If the DSS score is equal to or higher than 3, biopsies was recommended to confirm the histological diagnosis.