Exome sequencing of pleuropulmonary blastoma reveals frequent biallelic loss of TP53 and two hits in DICER1 resulting in retention of 5p-derived miRNA hairpin loop sequences.

Pleuropulmonary blastoma is a rare childhood malignancy of lung mesenchymal cells that can remain dormant as epithelial cysts or progress to high-grade sarcoma. Predisposing germline loss-of-function DICER1 variants have been described. We sought to uncover additional contributors through whole exome sequencing of 15 tumor/normal pairs, followed by targeted resequencing, miRNA analysis and immunohistochemical analysis of additional tumors. In addition to frequent biallelic loss  of TP53 and mutations of NRAS or BRAF in some cases, each case had compound disruption of DICER1: a germline (12 cases) or somatic (3 cases) loss-of-function variant plus a somatic missense mutation in the RNase IIIb domain. 5p-Derived microRNA (miRNA) transcripts retained abnormal precursor miRNA loop sequences normally removed by DICER1. This work both defines a genetic interaction landscape with DICER1 mutation and provides evidence for alteration in miRNA transcripts as a consequence of DICER1 disruption in cancer.

CRTC1 rearrangements in the absence of t(11;19) in primary cutaneous mucoepidermoid carcinoma.

BACKGROUND: Mucoepidermoid carcinoma (MEC) of the skin is an uncommon neoplasm with a remarkable resemblance to MEC of the salivary glands. The latter has been shown to harbour an oncogenic translocation resulting in a fusion gene consisting of exon 1 of CRTC1/MECT1/TORC1 at 19p and exons 2-5 of MAML2 at 11q. OBJECTIVES: While t(11;19) and rearrangements of the involved loci have been demonstrated in MEC of the salivary gland and other sites, it remains to be determined if morphological similarities in cutaneous MEC are reflected at the molecular level. METHODS: Cases of cutaneous MEC were defined by three histopathological features: (i) cystic dermal nodule with (ii) overlying intact epidermis and (iii) presence of three cell types (squamoid, intermediate, mucinous), and characterized by reverse transcription-polymerase chain reaction (RT-PCR), interphase fluorescent in situ hybridization (FISH) and immunohistochemistry. RESULTS: Eight primary cutaneous MECs were analysed. All informative cases showed CRTC1 rearrangements; none of the cases had MAML2 rearrangements or the presence of t(11;19) by RT-PCR. One case of primary MEC of the breast showed amplification of MAML2 in the absence of CRTC1 or t(11;19). Two MECs metastatic to the skin, histologically identical to primary cutaneous MEC, were included, one of which harboured the CRTC1-MAML2 fusion gene by RT-PCR, verified by interphase FISH and sequencing. CONCLUSIONS: MEC of the skin harbours CRTC1 rearrangements, a molecular finding that reflects morphological similarities between glandular and cutaneous MEC. The absence of oncogenic t(11;19) or MAML2 aberrations in our series, which is the largest reported, may explain the innocuous clinical behaviour of this uncommon adnexal tumour.

Genomic aberrations are rare in urothelial neoplasms of patients 19 years or younger.

Urothelial neoplasms in patients 19 years of age or younger are rare, and the data regarding clinical outcome are conflicting. Molecular data are not available. Urothelial tumours from 14 patients aged 4 to 19 years were analysed, including FGFR3 and TP53 mutation screening, comparative genomic hybridization (CGH), UroVysion FISH analysis, polymerase chain reaction for human papillomavirus (HPV), microsatellite analysis using the NIH consensus panel for detection of microsatellite instability (MSI) and six markers for loss of heterozygosity on chromosome arms 9p, 9q, and 17p and immunohistochemistry for TP53, Ki-67, CK20 and the mismatch repair proteins (MRPs) hMSH2, hMLH1, and hMSH6. Based on the 2004 WHO classification, one urothelial papilloma, seven papillary urothelial neoplasms of low malignant potential (PUNLMPs), five low-grade, and one high-grade papillary urothelial carcinoma were included. No multifocal tumours were found and recurrence was seen in only one patient with a urothelial papilloma. All patients were alive with no evidence of disease at a median follow-up of 3.0 years. We found no mutations in FGFR3, deletions of chromosome arms 9p, 9q or 17p, MSI or MRP loss, or HPV positivity in any of the patients. Three cases showed chromosome alterations in CGH analyses, urothelial dedifferentiation with CK20 overexpression, or aneuploidy, and one TP53 mutation with TP53 overexpression was found. Urothelial neoplasms in people younger than 20 years are predominantly low grade and are associated with a favourable clinical outcome. Genetic alterations frequently seen in older adults are extremely rare in young patients. Urothelial neoplasms in children and young adults appear to be biologically distinct and lack genetic instability in most cases.

Lipofibromatosis presenting as a pediatric neck mass.

Lipofibromatosis is a recently described, benign neoplasm that presents in the pediatric population [J.F. Fetsch, M. Miettinen, W.B. Laskin, M. Michal, F.M. Enzinger, A clinicopathologic study of 45 pediatric soft tissue tumors with an admixture of adipose tissue and fibroblastic elements, and a proposal for classification as lipofibromatosis, Am. J. Surg. Pathol. 24 (2000) 1491-1500]. It is a rare soft tissue tumor histologically distinct from other fibromatoses such as juvenile fibromatosis, fibrous hamartoma of infancy, calcifying aponeurotic fibroma, and lipoblastoma. Distinguishing histopathologic features of lipofibromatosis include abundant and disorganized adipose lobules traversed by bundles of spindled fibroblast-like cells. It most commonly presents in the extremities. We present a case involving a young girl, which we believe represents the first report of lipofibromatosis involving the neck.

Chromosome 22q dosage in composite extrarenal rhabdoid tumors: clonal evolution or a phenotypic mimic?

Composite extrarenal rhabdoid tumors (CERTs) represent a diverse group of neoplasms with rhabdoid shape in combination with one of several distinctive tumor types. Like the classic renal and extrarenal malignant rhabdoid tumor (MRT), as well as the atypical teratoid/rhabdoid tumor (AT/RT) of the central nervous system, CERTs typically show aggressive clinical behavior. Deletions and mutations of the INII gene on 22q11.2 have been identified in most classic MRTs and AT/RTs; however, it is not known whether the rhabdoid components in CERTs have similar genetic abnormalities. Using fluorescence in situ hybridization (FISH) on archival, paraffin-embedded tissue with a commercially available probe in close proximity to the INII locus (bcr), as well as other chromosome 22 probes, we studied 4 cases of MRT, 13 of AT/RT, and 16 of CERT (3 melanoma, 4 meningioma, 7 carcinoma, 1 rhabdomyosarcoma, and 1 neuroblastoma). Deletion of the 22q11.2 locus was demonstrated in 10 (77%) of 13 AT/RTs and 3 (75%) of 4 MRT, including 1 congenital MRT. Of the 16 CERTs, only 2 (a rhabdoid meningioma and a carcinoma with rhabdoid features; 13%) harbored a deletion at this locus. This difference was statistically significant (P <.001). We conclude that deletion of 22q11.2, typical of most classic MRTs and AT/RTs, is infrequently seen in CERTs. This suggests that the rhabdoid component of CERTs does not evolve by way of the genetic alteration characteristic of MRTs or AT/RTs, but represents instead a distinct phenotype shared by a number of tumors as they undergo anaplastic progression.

Visceral primitive peripheral neuroectodermal tumors: a clinicopathologic and molecular study.

Ewing sarcoma-primitive neuroectodermal tumor (EWS/PNET) belongs to the group of pediatric small round blue cell tumors; although EWS/PNET is classically a tumor of the soft tissue or bone in children and young adults, individual cases have been described in patients of all ages. A group of chromosomal translocations involving the EWS gene and a member of the Ets transcription factor family of genes has been detected in EWS/PNET, and heterogeneity in the precise breakpoint of the translocation has been shown to generate a group of related fusion transcripts that may have prognostic significance. Within the last decade, the clinicopathologic spectrum of EWS/PNET has been markedly expanded by recognition that the tumor may also have a visceral origin. To determine whether visceral EWS/PNET has the same pattern of genetic alterations and range of fusion transcripts as EWS/PNET of bone and soft tissue, we performed reverse-transcription polymerase chain reaction-based testing of formalin-fixed, paraffin-embedded tissue from a series of visceral tumors for which the diagnosis of EWS/PNET was well established. Together with additional cases compiled from the literature, EWS-Fli1 (or a related fusion transcript) was present in 18 of 19 visceral EWS/PNET, with a distribution of transcript types not statistically different from EWS/PNET of soft tissue and bone (P >.05, chi(2) test). These results firmly establish the genetic relationship between EWS/PNET of visceral sites, soft tissue, and bone.

Anaplastic lymphoma kinase (ALK) expression in the inflammatory myofibroblastic tumor: a comparative immunohistochemical study.

Inflammatory myofibroblastic tumor (IMT) is an uncommon mesenchymal neoplasm with a variable histologic appearance that may mimic other spindle cell processes, particularly nodular fasciitis, desmoid tumor, and in intra-abdominal locations, gastrointestinal stromal tumor. Recently, gene fusions involving ALK at chromosome 2p23 have been described in IMTs. The resultant ALK protein overexpression in the myofibroblastic component of these tumors is detectable by immunohistochemistry. We examined 73 IMTs, 20 cases of nodular fasciitis, 15 desmoid fibromatoses, and 15 gastrointestinal stromal tumors by immunohistochemistry using ALK-11, a rabbit polyclonal antibody that recognizes the C-terminus of the protein. ALK positivity was detected in 44 of 73 (60%) IMTs. All cases of nodular fasciitis, desmoid fibromatosis, and gastrointestinal stromal tumors were ALK negative (p < 0.001). These findings demonstrate that ALK positivity is common in IMTs, and immunohistochemistry using anti-ALK antibodies can be helpful in the differential diagnosis of these neoplasms. In addition, anti-ALK staining seems to correlate with those IMTs that have the typical tri-patterned histologic appearance and clinical presentation, providing additional support to the premise that IMT is a distinctive clinicopathologic entity within the broad category of inflammatory pseudotumors.

A role for fluorescence in situ hybridization detection of chromosome 22q dosage in distinguishing atypical teratoid/rhabdoid tumors from medulloblastoma/central primitive neuroectodermal tumors.

It has been postulated that infants with medulloblastomas/central primitive neuroectodermal tumors (MB/PNET) may fare worse than older patients because some of them harbor unrecognized atypical teratoid/rhabdoid tumors (AT/RT), rare intracranial neoplasms that are typically unresponsive to therapy and rapidly fatal. Although small primitive cells are common to both entities, chromosome 22q11.2 deletions are common only in AT/RTs. Using fluorescence in situ hybridization (FISH) on archival, paraffin-embedded biopsy tissue with commercially available probes to 22q11.2, the region associated with RTs, we studied 8 cases of AT/RT, 12 cases of MB/PNET, and 4 cases of primitive central nervous system (CNS) neoplasms, which were difficult to classify. 22q Deletions were identified in 6 of 8 (75%) conventional AT/RTs and 0 of 12 (0%) children with classic MB/PNET. Of the 4 originally "difficult to classify" cases, 3 had deletions of 22q. In light of the FISH results, review of the morphology and immunophenotype resulted in 3 tumors being reclassified as AT/RTs and 1 as a large cell MB. These 4 cases highlight the potential diagnostic use of FISH for selected cases of primitive CNS malignancies in children and substantiate the notion that misdiagnosed AT/RTs may, in part account for the worse prognosis associated with "MB/PNET" in children younger than 2 years of age.

Primitive neuroectodermal tumors of the biliary and gastrointestinal tracts: clinicopathologic and molecular diagnostic study of two cases.

Primitive neuroectodermal tumor (PNET) is a prototypic malignant small round cell tumor of childhood that is characterized in most cases by t(11;22) resulting in an EWS-FLI1 gene fusion. Once thought to be uncommon, PNET now accounts for almost 20% of malignant soft tissue tumors in children. Increased recognition of PNET is partly due to advances in immunohistochemistry and molecular diagnostics, which have led to the identification of the tumor in non-classical sites. We report the clinical, histologic, immunohistochemical, and molecular findings of two visceral PNETs of the digestive system--one involving the small intestine and the other involving the hepatic duct. Histologically, each tumor was composed of malignant small cells growing in sheets, nests, and lobules; the tumor cells of both cases showed characteristic immunoreactivity for vimentin and O13 (CD99). Reverse transcription-polymerase chain reaction (RT-PCR) analysis for t(11;22) using nested primers was performed with RNA extracted from paraffin-embedded, formalin-fixed tissue and demonstrated an EWS exon 7 to FLI1 exon 5 fusion in both cases, confirmed by Southern blot hybridization and DNA sequence analysis. These results illustrate the expanded clinicopathologic profile of PNET, and demonstrate that visceral PNETs, despite their unusual sites of presentation, maintain the characteristic immunohistochemical and genetic features of PNETs at more conventional sites.

Undifferentiated embryonal sarcoma with unusual features arising within mesenchymal hamartoma of the liver: report of a case and review of the literature.

Undifferentiated embryonal sarcoma (UES) is a rare and highly malignant hepatic neoplasm, affecting almost exclusively the pediatric population. It has replaced malignant mesenchymoma, under which diagnostic term the first three cases were described. A link between embryonal sarcoma and mesenchymal hamartoma of the liver (MHL) has long been proposed, because of clinicopathologic overlaps of these entities; however, until recently, this association remained tenuous. Cases of UES arising in a background of mesenchymal hamartoma of the liver have previously been reported in two teenage girls. Discovery of a similar genetic abnormality in MHL and UES has clinched the supposed link between them. There have also been two reports of UES with prominent cystification, one associated with peripheral eosinophilia, and thereby masquerading as hydatid cyst of the liver. We report a case of UES arising in a young boy with MHL, with unusual histologic features, including large mesothelial-lined cysts and ectopic adrenal cortical tissue under Glisson's capsule.

Diagnostic gold standard for soft tissue tumours: morphology or molecular genetics?

The recognition of recurrent genetic alterations in specific tumour types has provided the basis for the reclassification of certain soft tissue neoplasms, and molecular analysis of patient material has the potential to provide both diagnostic and prognostic information. In this review, we evaluate the role of molecular genetic testing as the prospective 'gold standard' for sarcoma diagnosis. Molecular genetic testing, as with every new method, promises to improve accuracy and to be more sensitive and less subjective, claims that have been made previously by histochemistry, electron microscopy and immunohistochemistry. Technical limitations in molecular assays, as well as more general specificity issues, decrease the clinical usefulness of molecular pathological testing significantly and suggest that, at present, molecular evaluation is best considered an ancillary technique that neither supersedes other ancillary techniques nor eclipses traditional pathological examination.

Malignant peripheral nerve sheath tumors with t(X;18). A pathologic and molecular genetic study.

Spindle cell sarcomas often present the surgical pathologist with a considerable diagnostic challenge. Malignant peripheral nerve sheath tumor, leiomyosarcoma, fibrosarcoma, and monophasic synovial sarcoma may all appear similar histologically. The application of ancillary diagnostic modalities, such as immunohistochemistry and electron microscopy, may be helpful in the differentiation of these tumors, but in cases in which these adjunctive techniques fail to demonstrate any more definitive evidence of differentiation, tumor categorization may remain difficult. Cytogenetic and molecular genetic characterization of tumors have provided the basis for the application of molecular assays as the newest components of the diagnostic armamentarium. Because the chromosomal translocation t(X;18) has been observed repeatedly in many synovial sarcomas, it has been heralded as a diagnostic hallmark of synovial sarcoma. To formally test the specificity of this translocation for the diagnosis of synovial sarcoma, RNA extracted from formalin-fixed, paraffin-embedded tissue from a variety of soft tissue and spindle cell tumors was evaluated for the presence of t(X;18) by reverse transcriptase-polymerase chain reaction. Although 85% of the synovial sarcomas studied demonstrated t(X;18), 75% of the malignant peripheral nerve sheath tumors in our cohort also demonstrated this translocation. We conclude that the translocation t(X;18) is not specific to synovial sarcoma and discuss the implications of the demonstration of t(X;18) in a majority of malignant peripheral nerve sheath tumors.

The enigmatic inflammatory pseudotumours: the current state of our understanding, or misunderstanding.

The inflammatory pseudotumour is a bona fide tumour in the sense of a mass lesion, which is known to present in virtually every anatomic region and organ from the central nervous system to the gastrointestinal tract. A fundamental question about pathogenesis is whether the inflammatory pseudotumour is a pseudo-or true neoplasm. There is evidence to support the argument that some of these fibroinflammatory masses are infection-associated and are often characterized by a proliferation of spindled histiocytes and/or dendritic cells, in contrast to a myofibroblastic proliferation in the other inflammatory pseudotumour, also known as the inflammatory myofibroblastic tumour.

WT1 staining reliably differentiates desmoplastic small round cell tumor from Ewing sarcoma/primitive neuroectodermal tumor. An immunohistochemical and molecular diagnostic study.

Differentiating desmoplastic small round cell tumor (DSRCT) from another similar small round cell tumor of childhood, the Ewing sarcoma/primitive neuroectodermal tumor (EWS/PNET), can be difficult because morphologic and immunohistochemical features overlap. We studied the predictive value of immunohistochemistry with an antibody to the C-terminal region of the Wilms tumor (WT1) protein for differentiating DSRCT from EWS/PNET in 24 malignant small round cell tumors that had been previously diagnosed as DSRCT or EWS/PNET by standard methods. We performed reverse transcriptase-polymerase chain reaction (RT-PCR) analysis in cases with available tissue as a confirmatory measure: 6 of 13 DSRCTs were informative by RT-PCR, and 6 of 6 showed an EWS-WT1 fusion; all 13 DSRCTs showed strong, definitive nuclear staining with the WT1 antibody. All 11 EWS/PNETs were WT1 antibody negative; 7 of 11 cases classified as EWS/PNET were informative by RT-PCR, and 7 of 7 showed an EWS-FLI-1 fusion. For cases in which the morphologic and immunohistochemical features are consistent with a diagnosis of DSRCT, WT1 antibody staining predicts the EWS-WT1 translocation with high sensitivity and specificity and is, therefore, useful for differentiating DSRCT from EWS/PNET when genetic information is unavailable.

Meningioma presenting as an intraoral mass in a patient with neurofibromatosis type 1.

A 77-year-old woman with neurofibromatosis type 1 presented with ill-fitting dentures due to intraoral extension of a right temporal fossa mass. Computed tomographic scanning demonstrated that the masticator space mass bowed the zygomatic arch and remodeled the lateral orbit and maxillary sinus walls, findings that were consistent with the clinical diagnosis of a neurofibroma with possible malignant transformation. However, light microscopic, immunohistochemical, and ultrastructural examination of tissue from an incisional biopsy specimen were diagnostic of meningioma. This case illustrates that the clinicopathologic differential diagnosis of an enlarging mass in patient with neurofibromatosis should include sporadic, unrelated neoplasms as well as tumors known to be associated with the syndrome.

Gliomatosis peritonei as a complication of a ventriculoperitoneal shunt: case report and review of the literature.

Gliomatosis peritonei, the implantation of neuroglial tissue upon the peritoneal surfaces, is a rare event most often associated with solid or immature teratomas of the ovary in young girls. The authors report a case of a 10-month-old girl with a ventriculoperitoneal shunt (VPS) who presented with bilateral inguinal hernias. Herniorrhaphy was uneventful. Microscopic examination of the hernia sacs showed exuberant mesothelial hyperplasia containing multiple nests of differentiated glial tissue. Subsequent computed tomography and laparoscopy disclosed normal ovaries with no evidence of intraabdominal or pelvic abnormalities. Gliomatosis peritonei in this case was attributed to transport of glial tissue from the cerebrospinal fluid into the peritoneal cavity via the shunt. With the exclusion of an ovarian germ cell neoplasm and in the presence of a VPS, the clinical course with regard to the glial implants in these children is uneventful. If it is appreciated that gliomatosis peritonei may be a complication of a VPS, an extensive clinical evaluation generally is unnecessary.

Malignant peripheral nerve sheath tumors with t(X;18). A pathologic and molecular genetic study.

Spindle cell sarcomas often present the surgical pathologist with a considerable diagnostic challenge. Malignant peripheral nerve sheath tumor, leiomyosarcoma, fibrosarcoma, and monophasic synovial sarcoma may all appear similar histologically. The application of ancillary diagnostic modalities, such as immunohistochemistry and electron microscopy, may be helpful in the differentiation of these tumors, but in cases in which these adjunctive techniques fail to demonstrate any more definitive evidence of differentiation, tumor categorization may remain difficult. Cytogenetic and molecular genetic characterization of tumors have provided the basis for the application of molecular assays as the newest components of the diagnostic armamentarium. Because the chromosomal translocation t(X;18) has been observed repeatedly in many synovial sarcomas, it has been heralded as a diagnostic hallmark of synovial sarcoma. To formally test the specificity of this translocation for the diagnosis of synovial sarcoma, RNA extracted from formalin-fixed, paraffin-embedded tissue from a variety of soft tissue and spindle cell tumors was evaluated for the presence of t(X;18) by reverse transcriptase-polymerase chain reaction. Although 85% of the synovial sarcomas studied demonstrated t(X;18), 75% of the malignant peripheral nerve sheath tumors in our cohort also demonstrated this translocation. We conclude that the translocation t(X;18) is not specific to synovial sarcoma and discuss the implications of the demonstration of t(X;18) in a majority of malignant peripheral nerve sheath tumors.

Fine-needle aspiration cytology of mesenchymal hamartoma of the chest wall.

We report on an uncommon entity, the so-called "chest wall chondromatous hamartoma" or "mesenchymal hamartoma of the chest wall" (MHCW), diagnosed by fine-needle aspiration (FNA) cytology in a 6-mo-old boy. Radiologic features were those of an aggressive lesion with rib expansion and destruction, that contrasted with aspirate smears showing bland cartilage and spindled mesenchymal elements. The clinicoradiographic features together with the FNA yield of mixed cellular elements aided in the correct diagnosis of MHCW.

Benign vascular neoplasms of the spleen with myoid and angioendotheliomatous features.

AIMS: To present the clinical light microscopic and immunophenotypic features of a distinctive vascular neoplasm of the spleen. METHODS AND RESULTS: Two of the splenic lesions arose in children, and one was found in an adult. They ranged from 19 to 40 mm diameter and histologically were quite similar. Sheets of large epithelioid cells with a spectrum of nuclear configurations ranging from oval and vesicular to twisted and hyperchromatic were noted in each case. Distinct or prominent nucleoli were present in many cells, and occasional cells had nuclear pseudoinclusions. In two cases, bands of basophilic, fibroblast-rich stroma with scattered chronic inflammatory cells were present. The mitotic rate ranged from 0/10 high-power fields (HPF) to 0.5/10 HPF in these epithelioid cells. The vascular nature of these tumours was manifested as a sieve-like array of round, erythrocyte-filled spaces, most with attenuated and cytologically bland lining cells. The polygonal, epithelioid cells exhibited the following phenotype: smooth muscle actin (SMA)+, muscle specific actin (MSA)+, vimentin+, CD31-, CD34-, CD21-, CD8-, CD68- (2/3 cases), S100-, while the lining cells were CD34+, vimentin+ and SMA-, with variable CD31 and factor VIII related antigen expression. Elongated SMA+, MSA+ cell processes were evident in one case, reminiscent of previously characterized myoid elements of the normal spleen. An uneventful follow-up was noted for all three patients. CONCLUSIONS: The histology and immunophenotype set these neoplasms apart from classic hamartomas, haemangiomas and previously characterized (haem)angioendotheliomas of the spleen, and may represent proliferations of myoid elements native to the spleen.

Pathology of the breast in children, adolescents, and young adults.

The pathologic spectrum of breast disease in children and adolescents is broad and includes entities more commonly seen in older patients. In general, the vast majority of breast masses in young patients are benign with fibroadenomas, gynecomastia, and macromastia accounting for the majority of surgical specimens. Malignant tumors are more likely to be secondary or metastatic than primary. Rhabdomyosarcoma and hematolymphoid tumors comprise a majority of malignant diagnoses in children. Primary carcinomas and sarcomas are rare, especially if sarcomas arising in the setting of cystosarcoma phyllodes are excluded.