A germline mutation of CDKN2A and a novel RPLP1-C19MC fusion detected in a rare melanotic neuroectodermal tumor of infancy: a case report.

BACKGROUND: Melanotic neuroectodermal tumor of infancy (MNTI) is exceptionally rare and occurs predominantly in the head and neck (92.8 % cases). The patient reported here is only the eighth case of MNTI presenting in an extremity, and the first reported in the fibula. CASE PRESENTATION: A 2-month-old female presented with a mass arising in the fibula. Exhaustive genomic, transcriptomic, epigenetic and pathological characterization was performed on the excised primary tumor and a derived cell line. Whole-exome analysis of genomic DNA from both the tumor and blood indicated no somatic, non-synonymous coding mutations within the tumor, but a heterozygous, unique germline, loss of function mutation in CDKN2A (p16(INK4A), D74A). SNP-array CGH on DNA samples revealed the tumor to be euploid, with no detectable gene copy number variants. Multiple chromosomal translocations were identified by RNA-Seq, and fusion genes included RPLP1-C19MC, potentially deregulating the C19MC cluster, an imprinted locus containing microRNA genes reactivated by gene fusion in embryonal tumors with multilayered rosettes. Since the presumed cell of origin of MNTI is from the neural crest, we also compared gene expression with a dataset from human neural crest cells and identified 185 genes with significantly different expression. Consistent with the melanotic phenotype of the tumor, elevated expression of tyrosinase was observed. Other highly expressed genes encoded muscle proteins and modulators of the extracellular matrix. A derived MNTI cell line was sensitive to inhibitors of lysine demethylase, but not to compounds targeting other epigenetic regulators. CONCLUSIONS: In the absence of somatic copy number variations or mutations, the fully transformed phenotype of the MNTI may have arisen in infancy because of the combined effects of a germline CDKN2A mutation, tumor promoting somatic fusion genes and epigenetic deregulation. Very little is known about the etiology of MNTI and this report advances knowledge of these rare tumors by providing the first comprehensive genomic, transcriptomic and epigenetic characterization of a case.

GI tract tumors with melanocytic differentiation.

Gastrointestinal (GI) tract tumors with melanocytic differentiation may present significant diagnostic challenges both for the pathologist and the clinician. This comprehensive review discusses the relatively common as well as rare entities that have melanocytic differentiation in the GI tract. Clinical, histologic, immunohistochemical and molecular features are discussed along with prognosis and differential diagnosis.

Pitfalls and uncertain prognosis in pathological diagnosis of psammomatous melanotic schwannoma.

A 20-year-old woman presenting with a pelvic mass identified as a psammomatous melanotic schwannoma (PMS) with atypical histological features was later found to have family history of cardiac myxomas consistent with Carney's complex. The BRAF V600E mutation was absent in the tumor.

BRAFV600E Mutation in Melanotic Neuroectodermal Tumor of Infancy: Toward Personalized Medicine?

The melanotic neuroectodermal tumor of infancy (MNTI) is a rare neoplasm that primarily affects the maxilla of infants during their first year of life. Complete resection is the conventional treatment and recurrence rates vary from 10% to 60%. The recurrent tumors grow more aggressively and can invade other anatomic structures, such as the nasal cavity, the orbit, and the skull base. The aggressive behavior of MNTIs may require radical resection, which may not be possible in some cases because of its rapid and invading growth together with invasion of vital structures. In these situations, adjunct radiotherapy or chemotherapy has been used. However, as there are no conclusive data regarding the molecular profile of this tumor, currently there is no targeted therapy that may be used in the treatment of selected aggressive cases. On the basis of MNTI similarities with melanomas, such as derivation from the neural crest cells and presence of large melanin-containing cells, we hypothesized that MNTIs also may harbor the BRAFV600E oncogenic mutation. We show for the first time that this important pediatric tumor may harbor the oncogenic BRAFV600E mutation, providing the first insights to their personalized treatment.

Melanotic neuroectodermal tumor of infancy: a molecular approach to diagnosis. Case report.

A case of melanotic neuroectodermal tumor of infancy arising from the transverse sinus is presented. The tumor was located on the outer surface of the dura and extended extracranially through the occipitomastoid suture. Two cell populations were observed: pigmented melanocyte-like cells and small neuroblast-like cells. Ultrastructural analysis revealed epithelial tumor cells and melanosomes at various stages. Expression of melanotransferrin messenger RNA transcripts within the tumor tissue was observed using a reverse transcriptase-polymerase chain reaction method in addition to immunohistological studies. The positive expression of melanotransferrin confirmed that this melanotic neuroectodermal tumor was derived from neural crest cells.

A novel PNET cell line with melanotic differentiation.

The primitive neuroectodermal tumor (PNET) cell line, ONS-99, was established from a human melanotic neuroectodermal tumor of infancy (MNTI). ONS-99 cells were polygonal adherent cells and transplantable to BALB/c-nu/nu mouse. ONS-99 cells were positive for NSE, HMB-45 (melanoma-associated antigen) and N-myc, but lacked the antigenic features of terminally differentiated neurons or glias. ONS-99 cells had many intermediate filaments in the cytoplasm and tight intercellular junctions with scant cytoplasmic structures by electron microscopy. To date, ONS-99 is the only example of an established PNET cell line with melanotic differentiation.

Recurrent melanotic neuroectodermal tumor of infancy: a proposal for treatment protocol with surgery and adjuvant chemotherapy.

The case of a 4-month-old male infant treated with combined surgery and chemotherapy for an aggressive recurrent melanotic neuroectodermal tumor of infancy (MNTI) on the top of the alveolar process of the mandible with a long-term follow-up is presented. Initial treatment comprised conservative local excision and curettage of the mandible. After several local recurrences and because radical surgical excision would give gross functional and aesthetic mutilation, finally complete, long-lasting remission was achieved with adjuvant chemotherapy, according to a neuroblastoma protocol (10-year follow-up). The reason for this protocol was because molecular genetic studies of this tumor showed loss of heterozygosity of chromosome 1p and gain of chromosome 7q analogue to neuroblastomas. A combination of surgery and chemotherapy should be the preferred treatment in case of a recurrence MNTI because optimal functional and aesthetic outcome.

Establishment and characterization of new cell lines derived from melanotic neuroectodermal tumor of infancy arising in the mandible.

Three cell systems (MINT1/2/3) derived from a melanotic neuroectodermal tumor of infancy (MNTI) arising in the mandible of a 1-month-old newborn boy have been established, and their cytological natures have been characterized. The cells had immunopositivities for pan-keratin, vimentin, neuron-specific enolase, S-100 protein and melanoma-associated antigen (HMB-45). These immunohistochemical phenotypes were basically the same as those observed in tissue sections, in which, synaptophysin, myelin basic protein, c-myc gene products, carcinoembryonic antigen, and epithelial membrane antigen were also immunolocalized in tumor cells. Karyotyping analyzes revealed that the chromosome numbers of the three cell systems ranged from 60 to 67 with 3n ploidies, and that there were many structural aberrations, such as del(11)(q13), del(22)(q13), add(2)(p11), add(7)(q22), extra copies for chromosomes 1, 2, 3, 5, 7, 9, 10, 11, 12, 16, 20, and 22, der(9)t(9;13)(p13;q12)add(9)(q34), and der(13;21)(q10;q10), which were shared by the three cell systems, while der(19)t(11;19)(q13;p13) was found in MINT1 and MINT3. When stimulated by endothelin-3 and vitamin D(3), the cells had spinous cell shapes with immunopositivities for HMB-45, neurofilament protein and glial fibrillary acidic protein, which indicated more neural differentiation. The established cell systems will be useful for further investigation on the molecular and genetic basis of MNTI to understand its pathogenesis, which is largely unknown.

Melanotic neuroectodermal tumor of infancy: a molecular genetic study.

Melanotic neuroectodermal tumor of infancy is a rare but well-recognized entity in pediatric pathology. However, the relationship of this tumor to other pediatric small cell tumors with neuroectodermal features (such as neuroblastoma, Ewing sarcoma/peripheral primitive neuroectodermal tumor, and desmoplastic small round cell tumor) is undetermined. Molecular genetic studies of melanotic neuroectodermal tumor of infancy have not been reported. We studied three typical cases of melanotic neuroectodermal tumor of infancy in an attempt to link this tumor to other small cell tumors with well-characterized molecular genetic changes. Tests performed included: detection of MYCN gene amplification and deletion of 1p (all 3 cases), and presence of the t(11;22)(q24;q12) and the t(11;22)(p13;q12) translocations (2 of 3 cases). None of these tests yielded positive results. Thus, there is no genetic basis at present to link melanotic neuroectodermal tumor of infancy to neuroblastoma, Ewing sarcoma/peripheral primitive neuroectodermal tumor, or desmoplastic small round cell tumor.

Biological functions of the ISWI chromatin remodeling complex NURF.

The nucleosome remodeling factor (NURF) is one of several ISWI-containing protein complexes that catalyze ATP-dependent nucleosome sliding and facilitate transcription of chromatin in vitro. To establish the physiological requirements of NURF, and to distinguish NURF genetically from other ISWI-containing complexes, we isolated mutations in the gene encoding the large NURF subunit, nurf301. We confirm that NURF is required for transcription activation in vivo. In animals lacking NURF301, heat-shock transcription factor binding to and transcription of the hsp70 and hsp26 genes are impaired. Additionally, we show that NURF is required for homeotic gene expression. Consistent with this, nurf301 mutants recapitulate the phenotypes of Enhancer of bithorax, a positive regulator of the Bithorax-Complex previously localized to the same genetic interval. Finally, mutants in NURF subunits exhibit neoplastic transformation of larval blood cells that causes melanotic tumors to form.