Clinicopathologic and cytogenetic analysis of malignant rhabdoid tumor of the central nervous system

Abstract

Malignant rhabdoid tumor (MRT) is an aggressive Case 1 neoplasm of infants and children with distinctive light microscopic, immunohistochemical, and ultrastructural features [1, 2]. Originally described in the kidney, the tumor also occurs in the liver [3], soft tissues [4], and paravertebral region [5]. Primary neoplasms of the brain such as primitive neuroectodermal tumors and astrocytomas have been found to arise in some patients with systemic MRTs [6-9]. Recently, primary MRT of the central nervous system (CNS MRT), unassociated with systemic tumors, has been described [1, 2,10-19]. In the sixteen reported cases for which clinical information is available, these tumors appear to be similar to nonCNS MRTs in that they are aggressive, and usually fatal. Abnormalities of chromosome 22 have been reported in four of five CNS MRTs in which cytogenetic analysis has been done [14, 20-22]; four of fourteen of the histologically similar non-CNS Case2 MRTs have abnormalities of chromosome 22 [3, 5, 22-26]. Because this primary brain tumor has been recognized less than a decade, and the number of karyotyped cases is small, we report three additional cases diagnosed at our pediatric hospital in the last three years. The combined clinical, histological, immunohistochemical, ultrastructural and cytogenetic studies in these three cases add to the evolving body of information about this unusual childhood CNS tumor. A previously healthy 3-year-old boy presented with lethargy, vomiting, and weakness of the right arm of one week's duration. On neurological examination, he had mild hemiparesis and right-sided hyperreflexia. Magnetic resonance imaging (MRI) showed a 6 cm inhomogeneous mass, with surrounding edema, in the left frontoparietal area. No other masses were seen on body computerized tomography (CT). The patient underwent a left frontal craniotomy with subtotal tumor resection. Postoperatively, he received 5,400 cGy of cranial irradiation. Follow-up head CR showed no evidence of tumor regrowth or craniospinal metastasis. He remains with mild residual right-sided weakness 3 years after surgery.