To correlate the immunostaining for INI1 protein and mutations in INI1 gene in possible rhabdoid tumours (RT) and atypical teratoid/rhabdoid tumours (AT/RT) seen at the Royal Children's Hospital in the last 10 years, and to study the clinicopathological features of those patients with negative nuclear staining.
Twenty tumours showing suggestive histological and/or immunohistochemical features of RT and AT/RT were selected. Immunohistochemistry for INI1 and molecular investigations for INI1 mutations were performed. The clinical features, histology and immunohistochemistry in those patients with negative nuclear staining were studied.
In seven tumours the nuclei stained uniformly for INI1. In none of these was an INI1 mutation detected. In 13 tumours nuclei showed no staining. In only ten of these was material available for molecular studies. Mutations were detected in nine. In these 13 patients, the primary tumour was in the central nervous system (CNS) in seven, in the soft tissue in three, in the liver in two and in the kidney in one. The age of presentation varied from 19 days to 7 years. Only five tumours showed large areas of rhabdoid cells. Most showed extensive non-diagnostic areas. In two an alternative diagnosis, ependymoma or myoepithelial carcinoma of soft tissue, was initially suggested. All the CNS tumours were positive for EMA, GFAP, and SMA. There were no long term survivors, but an occasional patient showed excellent response to intensive chemotherapy.
In this small series, there is a strong correlation between the loss of INI1 immunostaining and the presence of an INI1 mutation suggesting that the former is a reliable marker for RT and AT/RT in children. As relatively few tumours showed uniform populations of rhabdoid cells, and some showed features suggesting another diagnosis, INI1 staining should be checked in all high grade CNS tumours and malignant extraCNS tumours where the diagnosis is unclear. The prognosis of RT is poor but medium term remission can be achieved in some patients with aggressive treatment.
"Most histopathology laboratories confirm the diagnosis of rhabdoid tumor based on loss of immunostaining for SMARCB1 protein in the tumor cell nuclei and this correlates well with the presence of inactivating SMARCB1 mutations and with homozygous deletion of the gene [3,4]. However there have been several reports of germ-line mutations in SMARCB1 in association with rhabdoid tumor and with other tumors including epitheloid sarcoma and familial schwannomatosis [4-9]. Germ-line mutations have been described in patients where the rhabdoid tumor has arisen at multiple sites ("rhabdoid predisposition syndrome") and in cases of familial rhabdoid tumor where more than one child in a family is affected . "
[Show abstract][Hide abstract] ABSTRACT: Rhabdoid tumors are rare cancers of early childhood arising in the kidney, central nervous system and other organs. The majority are caused by somatic inactivating mutations or deletions affecting the tumor suppressor locus SMARCB1 [OMIM 601607]. Germ-line SMARCB1 inactivation has been reported in association with rhabdoid tumor, epitheloid sarcoma and familial schwannomatosis, underscoring the importance of accurate mutation screening to ascertain recurrence and transmission risks. We describe a rapid and sensitive diagnostic screening method, using high resolution melting (HRM), for detecting sequence variations in SMARCB1.
Amplicons, encompassing the nine coding exons of SMARCB1, flanking splice site sequences and the 5' and 3' UTR, were screened by both HRM and direct DNA sequencing to establish the reliability of HRM as a primary mutation screening tool. Reaction conditions were optimized with commercially available HRM mixes.
The false negative rate for detecting sequence variants by HRM in our sample series was zero. Nine amplicons out of a total of 140 (6.4%) showed variant melt profiles that were subsequently shown to be false positive. Overall nine distinct pathogenic SMARCB1 mutations were identified in a total of 19 possible rhabdoid tumors. Two tumors had two distinct mutations and two harbored SMARCB1 deletion. Other mutations were nonsense or frame-shifts. The detection sensitivity of the HRM screening method was influenced by both sequence context and specific nucleotide change and varied from 1: 4 to 1:1000 (variant to wild-type DNA). A novel method involving digital HRM, followed by re-sequencing, was used to confirm mutations in tumor specimens containing associated normal tissue.
This is the first report describing SMARCB1 mutation screening using HRM. HRM is a rapid, sensitive and inexpensive screening technology that is likely to be widely adopted in diagnostic laboratories to facilitate whole gene mutation screening.
BMC Cancer 12/2009; 9(13):437. DOI:10.1186/1471-2407-9-437 · 3.36 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: INTRODUCTION: We describe a case of genetically proven atypical teratoid/rhabdoid tumor (ATRT), showing ultrastructural evidence of ependymal differentiation. Such differentiation has not been reported so far in ATRT. CONCLUSION: This finding supports the concept that ATRTs as the majority of central nervous system embryonal tumors may derive from an immature and pluripotent neuroectodermal cell capable of differentiating along multiple lineages.
Child s Nervous System 07/2009; 25(12):1627-31. DOI:10.1007/s00381-009-0926-3 · 1.11 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Malignant rhabdoid tumors (MRTs) are aggressive and often fatal; the Surveillance, Epidemiology, and End Results (SEER) database offers an opportunity to study this rare malignancy.
From the SEER database, we extracted records of patients with a reported diagnosis of MRT and analyzed them for clinical features and survival rates by univariate and multivariate analyses.
For the 229 patients included in our data, who were diagnosed from 1986 to 2005, primary tumors were located in the central nervous system (CNS) (35%), kidneys (20%), and extra-renal non-cranial sites (ERNC-MRTs) (45%). Most patients with renal and CNS tumors were less than 18 years old (87% and 96%, respectively) while more than half of the patients with ERNC-MRTs (61%) were adults. Among staged tumors, 23% were localized, 34% regional, and 43% distant. Renal tumors had significantly more metastatic disease (47%; P = 0.006) than ERNC-MRTs. The estimated 5-year survival for the entire group was 33 +/- 3.4% (SE). Univariate and multivariate analyses showed that age at diagnosis (2-18 years), localized stage of tumors, and use of radiotherapy were significantly associated with improved survival. Adults had a better outcome than young children (<2 years old) but a poorer outcome than older children (2-18 years old); tumor stage, but not radiotherapy use, affected outcome in adults. The survival and prognostic factors of children diagnosed before and after 2000 did not differ significantly.
Our population-based study indicates that age at diagnosis, tumor stage, and use of radiotherapy favorably impact survival rates of patients with MRTs.
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