Intraspinal atypical teratoid/rhabdoid tumor

Abstract

Objective To investigate the clinicopathological features of atypical teratoid/rhabdoid tumor (AT/RT) occurred in the spinal cord.  Methods The clinical manifestations, imaging, histopathological features and immunophenotype were analyzed in one case of AT/RT, and relevant literatures were reviewed.  Results A 12-year-old male patient presented gradually aggravated pain of both lower extremities. The patient was gradually not able to stand, and then developed to be paralyzed and could not turn over by himself. Spinal MRI revealed abnormal signals in the lumbosacral portion of spinal cord, and exhibited heterogeneous enhancement after contrast. The lesion was totally removed under microscopy. Histologically, the tumor was invasive, with diffusely distributed tumor cells and old
hemorrhage. Some tumor cells were immature cells with small volume, obvious atypia and hyperchromatic nuclei. Others presented classic rhabdoid features: round to oval cells, eccentrically placed and vacuolar nuclei with prominent nucleoli, and hyperchromatic cytoplasm with eosinophilic round inclusion bodies. Tumor stroma showed mucoid degeneration. Immunohistochemical staining showed partial positivity in the cytoplasm of tumor cells for vimentin (Vim) and smooth muscle actin (SMA). Tumor cells were negative for synaptophysin (Syn), chromogranin A (CgA), S-100 protein (S-100) and oligodendrocyte transcription factor-2 (Olig-2). Besides, tumor cells lacked nuclear expression of integrase interactor 1 (INI1). Ki-67 labeling index was 15%-20%. Final pathological diagnosis was AT/RT. After operation the patient was treated by adjuvant chemotherapy and radiotherapy, and symptoms of lower limbs were improved markedly. The patient was admitted for 23 d (until the end of first chemotherapy), and was followed up for 8 months after discharge without tumor recurrence.  Conclusions AT/RT rarely occurs in spinal cord. The clinical and imaging manifestations are not specific, so a definite diagnosis mainly depends on histological and immunohistochemical features. Especially, lack of nuclear expression of INI1 in tumor cells is the characteristic marker of AT/RT.

DOI: 10.3969/j.issn.1672-6731.2016.06.006