LAUSR

Dear Editor: There has been no report about dumbbell-shaped atypical teratoid rhabdoid tumor (AT/RT) to the best of our knowledge. We had a previously healthy 3-year-old boy presented with weakness in the right upper extremity (UE). He acutely deteriorated over the next week, resulted in quadriparesis and urinary/fecal incontinence. Magnetic resonance imaging (MRI) showed an ellipsoid intradural extramedullary tumor at the level of C3–5 compressing the spinal cord posteriorly. The axial view at the level of C4–5 demonstrated the dumbbell shape tumor extending through the neural foramen of C4–5 (Fig. 1a– d). In order to decompress the spinal cord, an urgent intradural tumor gross total resection was performed. Postoperative MRI showed completely resected intradural tumor. The histopathological findings showed diffusely proliferating atypical cells with prominent nucleoli and extensive necrotic areas. The atypical cells stained negative with integrase interactor (INI1) and positive with vimentin, smooth muscle actin, epithelial membrane antigen, and cytokeratin, which led us to the final diagnosis of AT/RT (Fig. 2a–h). After the final diagnosis, he was started on the Boston protocol chemoradiation therapy [1]. His neurological function gradually improved and the MRI taken 5 months from the start of chemotherapy showed disappearance of extradural tumor without recurrence of intradural tumor. AT/RT is a rare malignant tumor accounting for 1– 2% of pediatric tumors of the brain [2]. Spinal AT/RT is even rare, and there have been only 20 published English reports on primary spinal AT/RT in children under age 18. Among them, 17 (85%) were intradural, 3 (15%) were extradural, and none had both extradural and intradural tumor. Dumbbell tumors are conceptually defined as having an intradural and extradural portion constricted at the intervertebral foreman or dural mater to assume an hourglass shape. They are not uncommon representing about 18% of spinal tumors and most likely have extramedullary origins. Most of the spinal dumbbell tumors (SDTs) are benign and schwannoma is the most common SDT [3]. However, there has been no report of dumbbell shape AT/RT. In the retrospective analysis of 118 cases of SDTs conducted by Ozawa et al., the imaging findings did not help in telling malignant from benign ones. Recently, Matsumoto et al. proposed a scoring system based on imaging findings to tell malignant SDTs from benign ones. Their scoring system resulted in 90% sensitivity and 85% specificity [4]. In our case, the differential diagnosis of dumbbell shape tumors includes schwannoma, neuroblastoma, malignant peripheral nerve sheath tumor, and sarcomas. Although schwannoma is most likely with a dumbbell-shaped tumor, his young age and the acute presentation were atypical for * Hideki Ogiwara [email protected]