Rat model of the human "Triton" tumor: direct genetic evidence for the myogenic differentiation capacity of schwannoma cells using the mutant neu gene as a cell lineage marker

Retroperitoneal malignant triton tumor in an infant: a case report and literature review

Malignant triton tumor (MTT) is a rare subtype of malignant peripheral nerve sheath tumor (MPNST) with rhabdomyoblastic differentiation. MTTs are solid tumors commonly located in the head, neck, extremities, and trunk. The presence of this tumor in an infant's retroperitoneum is extremely rare, and prompted the authors to report this case with reference to existing literature.

Malignant triton tumor of the gluteal region in a patient unaffected by neurofibromatosis: A case report

Malignant triton tumor (MTT) is a rare variant of malignant peripheral nerve sheath tumor (MPNST) made up of both malignant schwannoma cells and malignant rhabdomyoblasts.

A 26-years-old male patient was admitted with an asymptomatic gluteal mass. Magnetic resonance imaging showed heterogeneous soft tissue mass and he underwent open biopsy. Malignant peripheral nerve sheath tumor was diagnosed. He was given adjuvant chemotherapy following the removal of the tumor with hip disarticulation. The tumor was diagnosed as “malignant triton tumor” based on pathological examination including immunohistochemical studies. There were no signs of metastasis but recurrence was observed at 9 months follow up.

MTT is usually associated with Neurofibromatosis 1 and located in head, neck region. In this case sporadic involvement of gluteal region and aggressive behavior of the lesion despite radical surgery was demonstrated.

Proceedings of the 2012 National Toxicology Program Satellite Symposium

The 2012 annual National Toxicology Program (NTP) Satellite Symposium, entitled "Pathology Potpourri," was held in Boston in advance of the Society of Toxicologic Pathology's 31st annual meeting. The goal of the NTP Symposium is to present current diagnostic pathology or nomenclature issues to the toxicologic pathology community. This article presents summaries of the speakers' presentations, including diagnostic or nomenclature issues that were presented, along with select images that were used for audience voting or discussion. Some lesions and topics covered during the symposium include eosinophilic crystalline pneumonia in a transgenic mouse model; differentiating adrenal cortical cystic degeneration from adenoma; atypical eosinophilic foci of altered hepatocytes; differentiating cardiac schwannoma from cardiomyopathy; diagnosis of cardiac papillary muscle lesions; intrahepatocytic erythrocytes and venous subendothelial hepatocytes; lesions in Rathke's cleft and pars distalis; pernicious anemia and megaloblastic disorders; embryonic neuroepithelial dysplasia, holoprosencephaly and exencephaly; and INHAND nomenclature for select cardiovascular lesions.

Tumor suppressor mutations and growth factor signaling in the pathogenesis of NF1-associated peripheral nerve sheath tumors: II. The role of dysregulated growth factor signaling

Patients with neurofibromatosis type 1 (NF1), one of the most common genetic disease affecting the nervous system, develop multiple neurofibromas that can transform into aggressive sarcomas known as malignant peripheral nerve sheath tumors (MPNSTs). Studies of human tumors and newly developed transgenic mouse models indicate that Schwann cells are the primary neoplastic cell type in neurofibromas and MPNSTs and that development of these peripheral nerve sheath tumors involves mutations of multiple tumor suppressor genes. However, it is widely held that tumor suppressor mutations alone are not sufficient to induce peripheral nerve sheath tumor formation and that dysregulated growth factor signaling cooperates with these mutations to promote neurofibroma and MPNST tumorigenesis. In Part I of this review, we discussed findings demonstrating that a loss of NF1 tumor suppressor gene function in neoplastic Schwann cells is a key early step in neurofibroma formation and that progression from neurofibroma to MPNST is associated with abnormalities of additional tumor suppressor genes, including p53, INK4A, andp27(kip1). In Part II of this review, we consider evidence that dysregulated signaling by specific growth factors and growth factor receptors promotes the proliferation, migration, and survival of neoplastic Schwann cells in neurofibromas and MPNSTs.

Radiation-induced malignant triton tumor associated with severe spinal cord compression

✓ Malignant triton tumor (MTT) is a variant of malignant peripheral nerve sheath tumors. The authors report a case of radiation-induced MTT in a patient with severe cervicothoracic cord compression and review the related literature. This 36-year-old man presented with pain and weakness in his left arm. His medical history was significant for a biopsy procedure involving the sampling of an aneurysmal bone cyst located at T1–3 near the left lung apex; this was performed 6 years prior to presentation and was followed by radiotherapy. Neurological examination demonstrated radicular findings involving the left C-8 and T-1 nerve roots. Neuroimaging studies revealed a large mass lesion extending from C-6 to T-2 along the vertebral column, invading the upper thoracic cavity and the adjacent lung apex, and infiltrating the paravertebral muscles. A subtotal resection was performed, but the tumor regrew extensively within a short time. It invaded the spinal canal and caused significant cord compression. The patient underwent surgery two more times for tumor debulking and to relieve progressive airway and spinal canal compromise. He eventually became quadriplegic, however, and died 13 months after diagnosis of MTT. This is the seventh case of radiation-induced MTT and the fifth of MTT with spinal canal involvement to be reported in the literature.

Constitutive activation of the neuregulin-1/ErbB receptor signaling pathway is essential for the proliferation of a neoplastic Schwann cell line

Neuregulin-1 (NRG-1) proteins promote Schwann cell survival, differentiation and proliferation during development. High levels of an NRG-like activity are also present in some human peripheral nerve sheath tumors, suggesting that NRG-1 isoforms may be involved in the development of these neoplasms. We examined the expression of NRG-1 and its receptors, the erbB membrane tyrosine kinases, in JS1 cells, a rapidly proliferating line derived from a chemically induced rat malignant peripheral nerve sheath tumor (MPNST). Relative to nontransformed Schwann cells, JS1 cells overexpress the NRG-1 receptor erbB3 and its erbB2 coreceptor; JS1 erbB2 transcripts show no evidence of the activating mutation commonly found in N-ethyl-N-nitrosourea-induced neoplasms. JS1 cells do not express the epidermal growth factor receptor (EGFR), a kinase implicated in the pathogenesis of a major subset of MPNSTs. JS1 cells also express mRNAs encoding multiple alpha and beta isoforms from the glial growth factor and sensory and motor neuron-derived factor NRG-1 subfamilies. Stimulation with NRG-1beta in the presence of forskolin produces a dose-dependent increase in JS1 DNA synthesis. Even in unstimulated JS1 cells, however, erbB2 and erbB3 are constitutively tyrosine phosphorylated. Reducing this constitutive phosphorylation with the specific erbB inhibitor PD158780 markedly impairs JS1 DNA synthesis. These observations support the hypothesis that NRG-1 isoforms and erbB kinases act in an autocrine and/or paracrine fashion to promote mitogenesis in JS1 cells. The absence of EGFR expression in JS1 cells suggests that constitutive activation of the NRG-1/erbB signaling pathway is an alternative means of inducing Schwann cell neoplasia.

Cytogenetic study of malignant triton tumor: a case report

Malignant triton tumor (MTT) is a highly malignant neoplasm, classified as a variant of malignant peripheral nerve sheath tumor (MPNST) with rhabdomyoblastic differentiation. Few cytogenetic studies of MTT have been reported using conventional cytogenetic analysis. Here, we report a comprehensive cytogenetic study of a case of MTT using G-banding, Spectral Karyotyping(), and fluorescence in situ hybridization (FISH) for specific regions. A complex hyperdiploid karyotype with multiple unbalanced translocations was observed: 48 approximately 55,XY,der(7)add(7)(p?)dup(7)[2],der(7) t(7;20)(p22;?)ins(20;19)[5],der(7)ins(8;7)(?;p22q36)t(3;8)t(8;20)[15],-8[5],-8[19],r(8)dup(8), +der(8)r(8;22)[4],-9[9],der(11)t(11;20)(p15;?)ins(20;19)[22],der(12)t(8;12)(q21;p13)[21],der(13) t(3;13)(q25;p11),-17,-19,der(19)t(17;19)(q11.2;q13.1),-20,-22,+4 approximately 7r[cp24]/46,XY[13]. The 1995 International System for Human Cytogenetic Nomenclature was followed where possible. Note that breakpoints were frequently omitted where only SKY information was known for a small part of an involved chromosome. Our analysis revealed some breakpoints in common with those previously reported in MTT, MPNST, and rhabdomyosarcoma, namely 7p22, 7q36, 11p15, 12p13, 13p11.2, 17q11.2, and 19q13.1. FISH showed high increase of copy number for MYC and loss of a single copy for TP53.

Second malignancies in children with neuroblastoma after combined treatment with 131I-metaiodobenzylguanidine

BACKGROUND

(131)I-metaiodobenzylguanidine ((131)I-MIBG) is selectively taken up by cells of neural crest origin, allowing targeted radiotherapy of tumors such as neuroblastoma (NB) and pheochromocytoma. Radiotherapy may provide additional benefits in the treatment of NB, with moderate side effects such as hematologic and thyroid toxicity. However, with longer follow-up, other complications might occur. We describe our experience with second cancers occurring in children treated with (131)I-MIBG and chemotherapy.

METHODS

The clinical records of 119 consecutive NB cases treated with (131)I-MIBG at a single institution between 1984 and 2001 were reviewed for the occurrence of a second malignant neoplasm (SMN).

RESULTS

Overall, five cases of SMN occurred in the study patients. In particular, two cases of myeloid leukemia, one of angiomatous fibrous histiocytoma, one of malignant schwannoma, and one case of rhabdomyosarcoma were detected. The schwannoma and the rhabdomyosarcoma developed within the residual neuroblastic mass after first-line therapy.

CONCLUSIONS

Should (131)I-MIBG treatment become more broadly employed in the therapeutic strategy for neuroblastoma, the risk of second cancer will have to be taken into consideration. The organization of an international registry of subjects treated with (131)I-MIBG might better define the frequency and features of second malignancies following this radiometabolic approach.

Molecular analysis of malignant triton tumors

Triton tumors are rare variants of malignant peripheral nerve sheath tumor (MPNST) with muscle differentiation, often seen in patients with neurofibromatosis 1 (NF1). Individuals affected with NF1 harbor mutations in the NF1 tumor suppressor gene and develop neurofibromas and MPNSTs. The NF1 gene is expressed in Schwann cells and its expression is lost in schwannian neoplasms, suggesting a role in malignant development. Separately, there is evidence that p53 suppressor gene mutations are involved in MPNSTs. To determine the role of the NF1 and p53 genes in the development of the malignant Triton tumor we examined 2 such tumors, 1 from a 3-year-old boy without clinical manifestations of NF1 and another from a 24-year-old man with NF1. Histological analysis of these tumors showed both neural and muscle differentiation with S-100 and desmin immunoreactivity, respectively. Reverse transcribed RNA polymerase chain reaction (RT-PCR) of NF1 mRNA showed NF1 expression in the sporadic tumor. Strong nuclear immunoreactivity for p53 was observed throughout the malignant population in both tumors. This was confirmed by loss of heterozygosity for p53 in the non-NF1 patient, suggesting that p53 is involved in both hereditary and sporadic Triton tumors. The finding of preserved NF1 gene expression in the non-NF1-related Triton tumor suggests that different genetic events predispose to the development of this rare neoplasm in sporadic cases.

Early loss of the retinoblastoma gene is associated with impaired growth inhibitory innervation during melanotroph carcinogenesis in Rb+/- mice

To better understand the cell lineage-specific character of retinoblastoma (Rb) gene inactivation during tumor formation, the earliest stages of spontaneous melanotroph carcinogenesis in Rb+/- heterozygous mice have been subjected to sequential analyses. The first atypical cells are detected in the pituitary intermediate lobe during a period corresponding to the cessation of melanotroph proliferation between 35 and 60 days after birth. Atypical cells contain no wild-type copy of the Rb gene and synchronously form early atypical proliferates (EAP) in the subsequent 30-60 day period. In contrast to surrounding mature melanotrophs with the wild-type Rb gene, Rb-negative cells in EAP continue to proliferate well past postnatal day 60, and fail to be innervated by growth inhibitory dopaminergic nerve terminals. Atypical melanotrophs remain competent for dopamine D2 receptor stimulation and undergo S-phase apoptosis in close proximity to nerve terminals. These results indicate a key role for the Rb protein in the onset of neuron-neuroendocrine cell interactions. This role may explain cell-type-specific neuroendocrine carcinogenesis associated with inactivation of the ubiquitously expressed Rb gene.

Development of malignant fibrous histiocytoma induced by 7,12-dimethylbenz[a]anthracene in the rat: characterization of early atypical cells

Morphologically atypical cells were first detected in the adjacent connective tissue 98 days after implanting a paraffin pill containing 2 mg of 7,12-dimethylbenz[a]anthracene (DMBA) into the subcutaneous tissues of rats. These cells subsequently formed groups and finally produced gross malignant fibrous histiocytomas (MFH). Early atypical cells were located between proliferating fibroblasts and histiocytes in the center of a fibrous capsule surrounding the DMBA pill. They exhibited a smooth cell surface, dilated rough endoplasmic reticulum, multiple Golgi complexes, and were often associated with newly formed collagen. These cells incorporated [3H]thymidine and [3H]proline intensively, and showed weak acid phosphatase activity but no features diagnostic of macrophages (microvilli, numerous lysosomes, high acid phosphatase and non-specific esterase activities, antigens recognized by monoclonal antibodies ED1 and OX-42 and vital staining with trypan blue). There was no evidence that atypical cells differentiated into muscle cells (no expression of desmin or the alpha-sarcomeric form of actin) or Schwann cells (no expression of S-100 protein). No point mutation in the neu gene at nucleotide 2007, specific for N-ethyl-N-nitrosourea- and DMBA-induced malignant rat schwannomas, was detected by polymerase chain reaction (PCR)-restriction fragment length polymorphism (RFLP) analyses. These results support the view that malignant fibrous histiocytoma is derived from immature fibroblasts exhibiting pronounced phenotypic diversity during the later stages of carcinogenesis.