Fusion of the ALK gene to the clathrin heavy chain gene, CLTC, in inflammatory myofibroblastic tumor

Inflammatory myofibroblastic tumor of the posterior mediastinum: an older adult case with anaplastic lymphoma kinase abnormalities determined using immunohistochemistry and fluorescence in situ hybridization

Inflammatory myofibroblastic tumor (IMT) is a rare neoplasm that usually occurs in children and young adults. Anaplastic lymphoma kinase (ALK) abnormalities in IMT, determined using immunohistochemistry and/or molecular genetic studies, including fluorescence in situ hybridization (FISH), have almost been limited to children and young adults. In elderly cases of IMT, these ALK abnormalities are very rare. We report on a case of IMT arising in the posterior mediastinum of a 59-year-old Japanese man that showed ALK abnormalities determined using immunohistochemistry and FISH, suggesting the neoplastic nature of a subset of IMTs in older patients similar to those in younger ones and the presence of an additional mechanism(s) that allows them to start to grow late.

Serological identification of breast cancer-related antigens from aSaccharomyces cerevisiae surface display library

A yeast cell surface display technology was used for the isolation and characterization of tumor antigens recognised by autologous or allogeneic breast cancer serum. More than 100 clones recognized by patient serum were isolated using high-through-put fluorescence activated cell sorting. Combined serological and sequence analysis confirmed that a number of proteins known to be overexpressed in breast cancer tissue could be detected. A recently identified small breast epithelial mucin almost exclusively expressed in mammary gland tissue was isolated as a mutated protein variant. Subsequent serological analysis using the yeast expression system for the wild-type and mutant form showed a strong recognition by patient sera, whereas no significant recognition was observed for the respective prokaryotically expressed proteins. The small breast epithelial mucin is present to a large extent in a membrane bound format and might be used for tumor targeting strategies.

Urachal inflammatory myofibroblastic tumor with ALK gene rearrangement: a study of urachal remnants

OBJECTIVES

Abnormalities of the urachus are rare among children and include a patent tract and cyst formation. These structures can also be affected by infection and abscess development. They are usually diagnosed during infancy and treated by surgical resection. Involvement of this remnant by either benign or malignant tumors is very infrequent. A few cases of mesenchymal tumors, such as desmoid tumor and leiomyoma, involving the urachus have been described in published reports.

METHODS

We studied an inflammatory myofibroblastic tumor arising from the urachus in a 10-year-old boy. In addition, we reviewed 101 cases of urachal remnants retrieved from the surgical pathology and autopsy files in the Department of Pathology at the Children's Hospital Boston diagnosed in the past 82 years.

RESULTS

The urachal inflammatory myofibroblastic tumor showed anaplastic lymphoma kinase (ALK) rearrangement by immunohistochemistry and fluorescence in situ hybridization techniques. No other neoplasms were diagnosed in the analyzed population.

CONCLUSIONS

We describe an example of inflammatory myofibroblastic tumor involving the urachus. Involvement of the urachus by tumors is rare, but these should be considered in the differential diagnosis of urachal lesions.

ALK-positive diffuse large B-cell lymphoma of the stomach associated with a clathrin-ALK rearrangement

ALK-positive diffuse large B-cell lymphoma is a rare, recently characterized lymphoma subtype that shows granular cytoplasmic ALK expression. This report describes a primary gastric ALK-positive B-lineage lymphoma in which a clathrin (CLTC)-ALK fusion was identified by RT-PCR and direct sequencing of the breakpoint. This confirmed the presence of t(2;17)(p23;q23) involving the CLTC gene and is only the 4th report of such a translocation in this lymphoma subtype and the first to describe this tumor within the stomach. As in previous reports, immunophenotyping showed the malignant cell to be a terminally differentiated B-lineage cell characterized by the absence of B-cell antigens and expression of antigens associated with plasma cell differentiation. This case confirms the existence of such a lymphoma subtype arising in extranodal locations and underscores the importance of detailed immunophenotyping and specialized molecular genetic investigations in confirming the diagnosis.

Expression of anaplastic lymphoma kinase in soft tissue tumors: an immunohistochemical and molecular study of 249 cases

Although anaplastic lymphoma kinase (ALK) has been considered a diagnostic marker specifying a subset of anaplastic large cell lymphomas and inflammatory myofibroblastic tumors (IMTs), the existence of this receptor in some other mesenchymal malignancies has been recently reported. We examined a wider variety of soft tissue tumors to further advance the survey of ALK status in mesenchymal lesions. ALK protein expression was evaluated immunohistochemically with 2 specific antibodies (ALK1 and 5A4) in 249 benign and malignant soft tissue tumors, and the expression of ALK transcripts and 8 types of ALK fusion transcripts was assessed using reverse transcription-polymerase chain reaction (RT-PCR) in 165 and 100 tumors, respectively. Moreover, ALK gene status was analyzed by interphase fluorescence in situ hybridization (FISH) in 17 tumors with ALK expression. Immunohistochemically, ALK protein was detected in 69 cases (28%), including IMTs (4 of 4), rhabdomyosarcomas (4 of 7), various lipogenic tumors (35 of 65), Ewing's sarcoma/peripheral primitive neuroectodermal tumors (6 of 10), malignant fibrous histiocytomas (8 of 37), leiomyosarcomas (3 of 18), and other non-IMT tumors (9 of 108); however, most of these, except the IMTs, displayed merely low-level expression. Although ALK transcripts were identified in 85 (52%) of the 165 cases examined by RT-PCR, the full-length (wild-type) ALK, rather than the truncated or chimeric forms detected in IMTs, predominated in most non-IMT tumors. Except for 2 IMTs, all cases with the expression of ALK messages displayed no detectable ALK fusion transcripts. More than 67% of the cases analyzed by both RT-PCR and immunohistochemical assays demonstrated concordant results. ALK gene amplification was found in 4 non-IMT tumors (2 leiomyosarcomas and 1 case each of rhadomyosarcoma and malignant fibrous histiocytoma) analyzed by FISH, and the rearrangement of this gene was identified in 2 IMTs. The current data expands the variety of non-IMT soft tissue tumors with ALK expression, and warrants further investigation of its underlying molecular mechanisms.

Anaplastic lymphoma kinase (ALK 1) staining and molecular analysis in inflammatory myofibroblastic tumours of the bladder: a preliminary clinicopathological study of nine cases and review of the literature

Inflammatory myofibroblastic tumours (IMFT) may arise at any anatomical site, including lung, soft tissues, retroperitoneum and bladder. Although morphologically similar, these lesions encompass a spectrum of entities with differing aetiology, ranging from reactive/regenerative proliferations to low-grade neoplasms with a risk of local recurrence, but no significant metastatic potential. Vesical IMFT usually presents as a polypoid mass with a pale firm cut surface and can be of considerable size, mimicking a malignant tumour clinically and radiologically. Its good outcome, however, warrants conservative surgical excision, emphasising the importance of identification and distinction from malignant tumours of the bladder that may require more radical surgery and/or adjuvant therapy. We conducted a preliminary retrospective, comparative immunocytochemical study of 20 bladder tumours, including nine IMFTs, five spindle cell (sarcomatoid) carcinomas, two rhabdomyosarcomas, two leiomyosarcomas and two neurofibromas. The results confirmed IMFT positivity for smooth muscle actin, desmin and cytokeratin in 78-89% cases, resulting in potential confusion with sarcomatoid carcinoma or leiomyosarcoma. In contrast, cytoplasmic anaplastic lymphoma kinase (ALK 1) staining was present in eight IMFT (89%), but was not seen in any other lesion examined. The ALK 1 staining was confirmed by fluorescence in situ hybridisation, with translocation of the ALK gene present in 15-60% tumour cells in four of six IMFT examined, but not in four cases of sarcomatoid carcinoma or three of leiomyosarcoma. In conclusion, ALK 1 staining may be of value in the distinction of vesical IMFT from morphologically similar entities, and often reflects ALK gene translocations in these lesions.

Myofibroblastic malignancies

Malignant tumors composed of myofibroblasts are increasingly being recognized, but their existence remains controversial. Currently accepted examples within this category represent spindle cell or pleomorphic neoplasms of the soft tissues with a spectrum of histological grades. Low- and intermediate-grade myofibrosarcomas are fascicular spindle cell neoplasms resembling fibrosarcoma or leiomyosarcoma. They infiltrate deep soft tissue with disproportionate involvement of head and neck sites and can recur locally but infrequently metastasize. They variably express myoid immunohistochemical markers, and their differential diagnosis includes benign myofibroblastic proliferations such as fasciitis and fibromatosis as well as other types of spindle cell sarcoma. High-grade (pleomorphic) myofibrosarcomas are an ultrastructurally defined subset of malignant fibrous histiocytoma, which they resemble in morphology and behavior. Inflammatory myofibroblastic tumor and infantile fibrosarcoma are neoplasms that have myofibroblastic features and have been included in this category, but they have distinctive genetic findings. This article reviews the concept of myofibrosarcoma and describes its variants.

Anaplastic lymphoma kinase proteins in growth control and cancer

The normal functions of full-length anaplastic lymphoma kinase (ALK) remain to be completely elucidated. Although considered to be important in neural development, recent studies in Drosophila also highlight a role for ALK in gut muscle differentiation. Indeed, the Drosophila model offers a future arena for the study of ALK, its ligands and signalling cascades. The discovery of activated fusion forms of the ALK tyrosine kinase in anaplastic large cell lymphoma (ALCL) has dramatically improved our understanding of the pathogenesis of these lymphomas and enhanced the pathological diagnosis of this subtype of non-Hodgkin's lymphoma (NHL). Likewise, the realisation that a high percentage of inflammatory myofibroblastic tumours express activated-ALK fusion proteins has clarified the causation of these mesenchymal neoplasms and provided for their easier discrimination from other mesenchymal-derived inflammatory myofibroblastic tumour (IMT) mimics. Recent reports of ALK expression in a range of carcinoma-derived cell lines together with its apparent role as a receptor for PTN and MK, both of which have been implicated in tumourigenesis, raise the possibility that ALK-mediated signalling could play a role in the development and/or progression of a number of common solid tumours. The therapeutic targeting of ALK may prove to have efficacy in the treatment of many of these neoplasms.

Myofibrosarcoma

Myofibrosarcomas are malignant tumours of myofibroblasts, which have been recognised for many years, but have become clearly defined only recently. They are low- or high-grade sarcomas that arise in soft tissue or bone in adults or children. Low-grade myofibrosarcomas are infiltrative tumours, usually in deep soft tissue, with a predilection for the head and neck region, which display a range of microscopic appearances from fasciitis-like to fibrosarcoma-like; all cases at least focally display nuclear pleomorphism. They express smooth-muscle actin and calponin, and some express desmin, but most lack h-caldesmon. Low-grade myofibrosarcomas can recur but rarely metastasise. Their differential diagnosis is from benign myofibroblastic proliferations, such as fasciitis and fibromatosis, as well as from fibrosarcoma and leiomyosarcoma. Pleomorphic myofibrosarcomas are high-grade pleomorphic sarcomas (malignant fibrous histiocytoma), which show ultrastructural evidence of myofibroblastic differentiation. They closely resemble malignant fibrous histiocytoma clinically and morphologically, but are more frequently actin positive. This article describes the low- and high-grade variants of myofibrosarcoma and other malignant tumours with myofibroblastic differentiation.

Translocation (2;11)(q31;q12) is recurrent in collagenous fibroma (desmoplastic fibroblastoma)

Collagenous fibroma (desmoplastic fibroblastoma) is a rare, benign tumor composed of spindle and stellate-shaped fibroblasts and myofibroblasts in a densely collagenous background. A t(2;11)(q31;q12) has been reported in one case of collagenous fibroma and a rearrangement of the 11q12 breakpoint in a second case. In the present study, we detected a t(2;11) identical to that previously described in a collagenous fibroma arising in the supraclavicular fossa of a 55-year-old man. This finding confirms the nonrandom association of t(2;11)(q31;q12) with collagenous fibroma.

ALK activation by the CLTC-ALK fusion is a recurrent event in large B-cell lymphoma

We present 3 cases of large B-cell lymphoma (LBCL) with a granular cytoplasmic staining for anaplastic lymphoma kinase (ALK). All of the cases showed striking similarities in morphology and immunohistochemical profile characterized by a massive monomorphic proliferation of CD20-/CD138+ plasmablast-like cells. In one of the cases, initially diagnosed as a null-type anaplastic large cell lymphoma (ALCL), the B-cell phenotype became evident only at recurrence. Fluorescent in situ hybridization (FISH) and molecular studies led to the detection of a CLTC-ALK rearrangement in all 3 cases, without any evidence of full-length ALK receptor expression. The associated t(2;17)(p23;q23) was demonstrated in the karyotype of 2 cases. Although a similar CLTC-ALK aberration was previously identified in ALK-positive T-/null cell ALCL and inflammatory myofibroblastic tumor, its association with ALK-positive LBCL seems to be specific and intriguing.

ALK-ATIC fusion in urinary bladder inflammatory myofibroblastic tumor

In this report, we describe an inflammatory myofibroblastic tumor (IMT) of the urinary bladder in a 46-year-old man. Tumor cells presented striking cytoplasmatic ALK immunopositivity. Cytogenetic and FISH analysis, by use of a multicolor chromosome 2 banding probe, revealed a 46,XY,der(2)(2pter-->2p23:2q35-->2q37:2p11-->2q35:2p23-->2p11:2q37-->2qter) karyotype. Subsequent FISH and RT-PCR analysis confirmed the ALK-ATIC chimeric fusion in tumor cells. This is the first evidence of a variant rearrangement involving the ATIC gene in IMT and the first cytogenetic description of an IMT originating from the urinary bladder.

Complex genomic rearrangement of ALK loci associated with integrated human Epstein-Barr virus in a post-transplant myogenic liver tumor

Epstein-Barr virus (EBV) is a ubiquitous viral agent, well known to be associated with lymphoid, epithelial, and smooth-muscle malignancies in immunocompromised individuals. This report describes a 10-year-old patient with an EBV-related liver tumor occurring after kidney transplantation. The neoplasm presented a phenotypic spectrum, ranging from a smooth-muscle tumor to an inflammatory pseudotumor (IPT). The neoplastic cells failed to disclose CD21, CD35, or ALK expression, the latter confirmed by reverse-transcription polymerase chain reaction. Cytogenetic analysis revealed a single clonal cell population showing 46,XY,del (2)(p23),der(3)t (2;3)(p23;q29),der(21) t(Y;21)(q12;p13) karyotype. By metaphase FISH analysis, the neoplastic cells demonstrated the presence of two molecularly different but related aberrant clones, one with the loss of one ALK allele and the second with translocation of the 3'end of ALK kinase domain on the der(3) chromosome. Using FISH with an EBV-specific and 3'end ALK DNA probes, a co-localization of the viral DNA and the ALK sequences was found on the der(3) chromosome. Metaphases with loss of rearranged ALK did not show integrated virus; instead, viral particles together with an associated 3'end ALK domain formed an ex-chromosomal, episomal-like type configuration. The interphase study, using dual-color 5'/3' end ALK FISH assay, revealed 30% of nuclei with only one fused signal, confirming the total loss of one ALK allele in the subset of tumor cells. A combined immunofluorescence and FISH study indicated this separate clonal variant to correspond to desmin-positive smooth-muscle cells. In contrast, desmin-negative myofibroblasts showed the presence of both normal and rearranged ALK alleles. Our results indicate that ALK locus may be a target of EBV integration, a hitherto unreported finding. Although the sustained clonal expansion in EBV-related smooth-muscle tumors/IPTs may depend on functions provided by the EBV oncogenic proteins, the tumor phenotype may be further modified by the secondary genomic rearrangements imposed by the virus during and/or after the integration event. In this respect, the observed phenotypic heterogeneity most likely reflects divergence during neoplastic progression, with the subsequent expansion of morphologically and molecularly distinct but cytogenetically related clones.

Recent advances in pediatric renal neoplasia

Over the past 6 years, molecular genetic studies have significantly advanced our understanding of pediatric renal neoplasms. The cellular variant of congenital mesoblastic nephroma (but not the classic variant) has been shown to bear the same t(12;15)(p13;q25) and ETV6-NTRK3 gene fusion as infantile fibrosarcoma, a tumor with which it shares morphologic and clinical features. Rhabdoid tumor of the kidney is characterized by deletion of the hSNF5/INI1 gene, which links it to other rhabdoid tumors of infancy that arise in the soft tissue and brain. Primary renal synovial sarcomas and renal primitive neuroectodermal tumors have become accepted entities, and likely comprise a subset of what had previously been termed "adult Wilms tumor." Renal carcinomas associated with Xp11.2 translocations that result in fusions involving the TFE3 transcription factor gene have been delineated, including a distinctive neoplasm that shares the identical gene fusion as alveolar soft part sarcoma. Most recently, a distinctive type of renal neoplasm with a t(6;11)(p21;q12) has been described, and the cloning of the resulting gene fusion links it to the Xp11 translocation carcinomas. Together, these last two translocation-associated tumors represent a significant proportion of pediatric renal cell carcinomas. This review highlights each of these recent advances.

Identification of CARS-ALK fusion in primary and metastatic lesions of an inflammatory myofibroblastic tumor

Inflammatory myofibroblastic tumor (IMT) is a rare childhood neoplasm. The natural history of this disease is poorly understood. Recently chromosomal rearrangements involving the anaplastic lymphoma kinase (ALK) gene have been implicated in this tumor. We have studied a case of ALK-positive soft tissue IMT showing clinical and morphologic features of malignancy. Interphase fluorescence in situ hybridization demonstrated ALK rearrangements in both primary and metastatic lesions. Rapid amplification of cDNA ends (5'RACE) identified cysteinyl-tRNA synthetase (CARS) gene fused to ALK, which predicts an in-frame chimeric protein with the preserved functional catalytic domain of ALK at the C terminus. Amplification and sequencing of tumor DNA confirmed the breakpoint at the genomic level. Restriction analysis of DNA from primary soft tissue and recurrent lung tumors showed identical patterns, indicating the same clonal origin of both lesions. Western blot analysis with C-terminus ALK antibody showed expression of an aberrantly sized chimeric protein of approximately 130 kd in tumor tissue. This is the second case of IMT demonstrating CARS as the ALK fusion partner, which confirms the recurring involvement of ALK in IMT by a common genetic mechanism. Moreover, identical clonality of separate lesions involving different sites supports metastasis in IMT.

A novel CLTC-TFE3 gene fusion in pediatric renal adenocarcinoma with t(X;17)(p11.2;q23)

A distinctive subset of renal carcinomas is associated with Xp11. 2 translocations and resulting TFE3 gene fusions (PRCC-TFE3, PSF-TFE3, NONO-TFE3, ASPL-TFE3), encoding related aberrant transcription factors. We report the cloning of a novel clathrin heavy-chain gene (CLTC)-TFE3 gene fusion resulting from a t(X;17)(p11.2;q23) in a renal carcinoma arising in a 14-year-old boy. The fusion transcript joined the 5' exons of CLTC on chromosome band 17q23 to the 3' exons of TFE3. CLTC encodes a major subunit of clathrin, a multimeric protein on cytoplasmic organelles, and is a known recurrent fusion partner of the ALK tyrosine kinase gene in anaplastic large-cell lymphoma and inflammatory myofibroblastic tumors. The predicted CLTC-TFE3 product retains the nuclear localization and DNA-binding domains of TFE3, but lacks the multimerization domain of CLTC. The present renal tumor demonstrated morphologic and immunohistochemical features of both PRCC-TFE3 and ASPL-TFE3 carcinomas, including strong nuclear immunoreactivity for the TFE3 C-terminal and only minimal expression of epithelial proteins. However, unlike most renal carcinomas, it also focally expressed melanocytic proteins. The present report highlights the promiscuity of certain genes involved in chromosomal translocations. Further analysis of the shared features of CLTC and other TFE3 fusion partners may shed light on the essential biology of TFE3 fusion proteins.

Molecular genetics of pediatric soft tissue tumors: clinical application

The application of molecular genetics to pediatric soft tissue tumors has grown tremendously over the last decade. It has resulted in the identification of novel genes that have provided us with an increased understanding of oncogenesis. Furthermore, these findings have identified diagnostic and potentially prognostic factors for patient management. Molecular diagnostic techniques, such as reverse transcription PCR (RT-PCR) and fluorescence in situ hybridization (FISH), have become important tools for evaluating pediatric soft tissue tumors. By detecting characteristic fusion genes, these techniques have greatly increased the diagnostic accuracy of histopathological classification. One of the exciting promises of the development of these molecular techniques is their ability to detect micrometastasis and minimal residual disease. Monitoring of minimal residual disease in pediatric soft tissue tumors by quantitative RT-PCR may provide important prognostic information. Furthermore, the potential development of targeted therapy based on the understanding of the molecular pathology of a specific soft tissue tumor may complement existing treatments and improve disease outcome.

ALK+, CD30-, CD20- large B-cell lymphoma containing anaplastic lymphoma kinase (ALK) fused to clathrin heavy chain gene (CLTC)

Pathological features and genomic basis of a rare case of ALK(+), CD30(-), CD20(-) large B-cell lymphoma were analyzed. A 36-year-old Japanese female was admitted because of lumbago and constitutional symptoms. Physical examination and laboratory tests showed anemia (hemoglobin, 7.5 g/dL), mild hepatosplenomegaly, and immunoglobin G (IgG) lambda-type monoclonal gammopathy (IgG, 2782 mg/dL). The lymphoma spread exclusively in extranodal sites such as bone marrow, liver, spleen, ovary, and muscle. Biopsy specimens obtained from the ovary showed monomorphic proliferation of large immunoblastic cells with basophilic cytoplasm, round-shaped nuclei with a high nuclear to cytoplasmic ratio, and prominent single nucleolus. Immunostaining with anti-anaplastic lymphoma kinase (ALK) antibody, ALK1, showed finely granular cytoplasmic staining pattern. These cells were also positive for epithelial membrane antigen, CD4, CD19, CD38, CD138, cytoplasmic IgG, and lambda chain, but negative for CD30 (Ber-H2), CD56, CD57, and other T- and B-cell markers. Southern blot analyses revealed that Ig heavy and lambda light chain genes, but not T-cell receptor (TCR) beta gene, were clonally rearranged. Chromosomal analyses by conventional G-banding, spectral karyotyping, and fluorescence in situ hybridization showed complex abnormality involving 2p23, and chromosome 2 was translocated to chromosome 17. As 2;17 translocation resulting in the fusion of clathrin heavy chain (CLTC) gene with ALK was previously reported in inflammatory myofibroblastic tumor, we performed reverse transcriptase-polymerase chain reaction and demonstrated that the lymphoma cells contained CLTC-ALK fusion transcript. Under the diagnosis of ALK(+), CD30(-), CD20(-) large B-cell lymphoma, she was treated with conventional combination chemotherapies. However, the lymphoma was primarily chemotherapy resistant, and the patient died 11 months after admission. We consider that this case confirms the existence of ALK(+), CD30(-), CD20(-) large B-cell lymphomas proposed by Delsol et al. (16) and further provides relevant information regarding their clinicopathological features and cytogenetics.

Inflammatory myofibroblastic tumor with predominant anaplastic lymphoma kinase-positive cells lacking a myofibroblastic phenotype

Inflammatory myofibroblastic tumor (IMT), synonymously referred to as inflammatory pseudotumor, is a distinctive mesenchymal lesion composed of spindle cells displaying morphological features of myofibroblasts admixed with considerable numbers of inflammatory cells. Recent genetic and molecular studies have shown that a subset of IMT is characterized by the expression of altered anaplastic lymphoma kinase (ALK) protein mostly resulting from rearrangements of the ALK gene such as TPM3-ALK, TPM4-ALK and CLTC-ALK fusion genes. We analyzed the ALK status in nine cases of IMT arising in various anatomical locations. Six cases showed immunohistochemical expression of the ALK protein, and two ALK-positive lesions examined by reverse transcription-polymerase chain reaction and a subsequent sequencing analysis harbored the TPM4-ALK fusion gene. Of note, the majority of ALK-positive tumor cells in four of the six lesions lacked the coexpression of myogenic markers including alpha-smooth muscle actin, a cytoskeletal protein indicating myofibroblastic differentiation, whereas a substantial number of tumor cells in the remaining two cases coexpressed ALK and alpha-smooth muscle actin and/or desmin. In an ultrastructural study of the lesion with predominant ALK-positive/actin-negative cells, spindle cells failed to demonstrate features of myofibroblasts such as intracytoplasmic bundles of thin filaments and dense bodies. The current findings suggest that ALK-positive cells in IMT are not always myofibroblastic but might be immature primitive mesenchymal cells.

Fusion of ALK to the Ran-binding protein 2 (RANBP2) gene in inflammatory myofibroblastic tumor

Inflammatory myofibroblastic tumor (IMT) is a rare mesenchymal proliferation of transformed myofibroblasts, with a prominent inflammatory cell component, that can mimic other spindle cell processes such as nodular fasciitis, desmoid tumor, and gastrointestinal stromal tumor. Genetic analyses have recently demonstrated rearrangements of anaplastic lymphoma kinase (ALK), located at 2p23, in a subset of IMTs. Molecular characterizations have identified ALK fusions involving tropomyosin-3 and -4 (TPM-3 and -4), the clathrin heavy chain (CLTC), and the cysteinyl-tRNA synthetase (CARS) genes as fusion partners. Here we describe two IMTs with a novel ALK fusion that involves the Ran-binding protein 2 (RANBP2) gene at 2q13, which normally encodes a large (358-kDa) nucleopore protein localized at the cytoplasmic side of the nuclear pore complex. The N-terminal 867 residues of RANBP2 are fused to the cytoplasmic segment of ALK in the 1,430-amino acid RANBP2-ALK chimeric protein. Myofibroblasts that express RANBP2-ALK exhibit nuclear membrane-associated ALK staining that is unique compared to the subcellular localization observed with other ALK fusions in IMT, presumably attributable to heteroassociation of the fusion with normal RANBP2 at the nuclear pore. These findings expand the spectrum of ALK abnormalities observed in IMT and further confirm the clonal, neoplastic nature of these lesions.

p53 Mutation and MDM2 amplification in inflammatory myofibroblastic tumours

AIMS

The pathogenic mechanism and predictive indicators of biological behaviour of inflammatory myofibroblastic tumour are poorly understood. We investigated molecular abnormalities of p53 and MDM2 in order to assess whether these play an important role in pathogenesis, and whether they also contribute to clinicopathological aggressive phenotype in inflammatory myofibroblastic tumour.

METHODS AND RESULTS

We compared the immunohistochemical expression of calponin, h-caldesmon, ALK, and p53 gene mutation and MDM2 gene amplification with clinicopathological findings in 15 cases of inflammatory myofibroblastic tumour. Histologically, cellular atypia was observed in five (33.3%) out of 15 cases. Local recurrences were observed in two (14.3%) of 14 informative cases, but no distant metastasis was observed. The expression of calponin (9/14; 64%) but not h-caldesmon (0/14; 0%) was seen, which suggested myofibroblastic differentiation. ALK expression was seen in eight (53.3%) out of 15 cases, particularly in patients under 40 years old. Nuclear expression of p53 protein was recognized in only one (6.7%) of 15 cases, and polymerase chain reaction single-strand conformation polymorphism followed by direct sequencing revealed p53 gene missense mutations in two (13.3%) of 15 cases. Nuclear expression of MDM2 was seen in four (26.7%) of 15 cases, and the MDM2 gene amplification was observed in two of the four cases.

CONCLUSION

Inflammatory myofibroblastic tumour shows a wide spectrum of cellular atypia and biological behaviour with p53 and MDM2 expression. However, the alterations in the p53 pathway seem not to play a major role in the pathogenesis of inflammatory myofibroblastic tumour.

Successful treatment of inflammatory myofibroblastic tumor with malignant transformation by surgical resection and chemotherapy

Inflammatory myofibroblastic tumor (IMT) is a tumor composed of myofibroblasts and a mixed inflammatory infiltrate that rarely undergoes malignant transformation. The authors present the case of a 7-year-old boy with an abdominal mass diagnosed as IMT with malignant transformation. The tumor recurred twice after attempts at resection and was initially treated with vincristine and etoposide. After a third recurrence and incomplete resection, he was treated with cisplatin, Adriamycin, and methotrexate. He is disease-free after 2 years, representing successful combined surgery and chemotherapy in the treatment of malignant IMT. The use of chemotherapy for aggressive myofibroblastic tumors is reviewed.

Molecular biology of anaplastic lymphoma kinase-positive anaplastic large-cell lymphoma

Anaplastic large-cell lymphoma (ALCL) provides an excellent example of how molecular insights into tumor pathogenesis are influencing and improving tumor classification. ALCL was described initially as a subtype of T-cell/null-cell lymphoma characterized by unusual tumor cell morphology and the expression of CD30. However, it was soon recognized that a subset of ALCLs contained chromosomal translocations involving anaplastic lymphoma kinase (ALK), a novel receptor tyrosine kinase gene. These rearrangements create chimeric genes encoding self-associating, constitutively active ALK fusion proteins that activate a number of downstream effectors, including phospholipase C-gamma, phosphoinositol 3'-kinase, RAS, and signal transducer and activator of transcription proteins, all of which seem potentially important in cellular transformation. Not all tumors classified as ALCLs have ALK rearrangements and, conversely, ALK rearrangements occur in lymphomas of widely varying morphology. Hence, only molecular markers can reliably identify ALK+ ALCL. The importance of doing so is reflected by clinical studies suggesting that ALK+ ALCLs have a significantly better prognosis than other aggressive peripheral T-cell or B-cell lymphomas, including ALK- ALCLs. The unique molecular pathogenesis of ALK+ ALCL is likely to lead to novel therapeutic approaches directed at specific inhibition of ALK or downstream effectors.

Identification of novel fusion partners of ALK, the anaplastic lymphoma kinase, in anaplastic large-cell lymphoma and inflammatory myofibroblastic tumor

ALK-positive anaplastic large-cell lymphoma (ALCL) has been recognized as a distinct type of lymphoma in the heterogeneous group of T/Null-ALCL. While most of the ALK-positive ALCL (ALKomas) are characterized by the presence of the NPM-ALK fusion protein, the product of the t(2;5)(p23;q35), 10-20% of ALKomas contain variant ALK fusions, including ATIC-ALK, TFG-ALK, CLTC-ALK (previously designated CLTCL-ALK), TMP3-ALK, and MSN-ALK. TMP3-ALK and TMP4-ALK fusions also have been detected in inflammatory myofibroblastic tumors (IMTs), making clear that aberrations of the ALK gene are not associated exclusively with the pathogenesis of ALK-positive ALCL. Here we report results of molecular studies on two lymphoma cases and one IMT case with variant rearrangements of ALK. Our study led to the detection of the CLTC-ALK fusion in an ALCL case and to the identification of two novel fusion partners of ALK: ALO17 (KIAA1618), a gene with unknown function, which was fused to ALK in an ALCL case with a t(2;17)(p23;q25), and CARS, encoding the cysteinyl-tRNA synthetase, which was fused to ALK in an IMT case with a t(2;11;2)(p23;p15;q31). These results confirm the recurrent involvement of ALK in IMT and further demonstrate the diversity of ALK fusion partners, with the ability to homodimerize as a common characteristic.

Calcifying fibrous 'pseudotumor': clinicopathologic study of 15 cases and analysis of its relationship to inflammatory myofibroblastic tumor

Calcifying fibrous pseudotumor (CFP) has been postulated to be a "late" stage of inflammatory myofibroblastic tumor (IMT). We analyzed 15 cases (8 females and 7 males; aged 1 to 65 years). The anatomic distribution was wide, including 3 cases each in neck, mesentery/omentum, and GI tract and 2 cases each in mediastinum and paratesticular sites. Follow-up information was available in 10 patients (range 4 to 228 months). Local recurrence occurred in 3 patients and was repeated in 2. Tumor size ranged from 0.6 to 25 cm. Lesions were well-circumscribed hypocellular spindle cell proliferations with dense stromal collagen, a lymphoplasmacytic infiltrate, and stromal calcifications. Features of conventional IMT were not seen. Immunostaining showed CD34 positivity in most cases as well as rare cells positive for smooth muscle actin and desmin, and consistent negativity for ALK-1 and S-100 protein. These findings suggest that CFP is a distinctive benign mesenchymal neoplasm with a low risk for recurrence and, therefore, best labelled as "calcifying fibrous tumor." There is no convincing evidence to support an association between CFP and IMT.

Intravascular inflammatory myofibroblastic tumors in infancy

Inflammatory myofibroblastic tumor (IMT), previously described as inflammatory pseudotumor, can occur at any age but is a recognized soft tissue tumor of childhood. Less than 10 previous cases have been described of IMT affecting the heart, in patients ranging from 5 months to 17 years of age. We present three unusual, but similar, cases of IMT in infants, which were all predominantly intravascular in location, one of which was associated with death due to angiodestructive lesions of the coronary and cerebral arteries. These cases demonstrate an apparently distinct phenotype, with a predominant intravascular location of the tumor. Furthermore, this series highlights the difficulty in categorizing such lesions as benign versus malignant on histological grounds alone. IMT should be considered in the differential diagnosis of unusual pediatric intravascular spindle cell lesions.

Chromosomal translocations and sarcomas

This review examines how the identification of tumor-specific translocations and fusion proteins has advanced the basic scientific and clinical understanding of sarcomas. Recent genetic advances, including the ASPL-TFE3 fusion of alveolar soft part sarcoma, the JAZF1-JJAZ1 fusion of endometrial stromal sarcoma, and HMGIC fusions in liposarcoma, are discussed. Next, the review addresses the ways in which molecular genetic data have influenced diagnostic and prognostic paradigms. For example, recent studies describe the detection of occult tumor cells and the identification of primary renal neoplasms that are genetically related to alveolar soft part sarcoma. In addition, the review discusses potential therapies based on the targeting of sarcoma-specific fusion proteins. These reports describe the potential use of Gleevec (STI571) for dermatofibrosarcoma protuberans and the use of tumor-specific fusion proteins as potential targets for immunotherapy. Finally, basic scientific findings are reviewed that elucidate, for example, the aberrant functions of SYT-SSX in chromatin remodeling and of EWS-FLI1 in transcription and mRNA splicing. These and other emerging models of tumorigenesis will help identify new therapeutic targets.

Leiomyosarcoma of the head and neck: a clinicopathological study

AIMS

The behaviour of leiomyosarcoma is site-related and there are few data on such tumours located in the head and neck. We studied the clinicopathological features of these lesions.

METHODS AND RESULTS

Cases diagnosed as leiomyosarcoma of the head and neck were retrieved from the archives of three institutions. Immunohistochemistry was performed and follow-up information was obtained. There were seven men and six women, aged 21-73 years, and lesions involved the neck (n=3), maxilla (n=4), buccal area (n=3), and maxillary sinus, nose, and pharynx (n=1 each). Tumours ranged from 10 to 80 mm. All tumours showed at least focally typical histological features of leiomyosarcoma with perpendicularly arranged fascicles of smooth muscle cells with blunt-ended nuclei, eosinophilic cytoplasm and paranuclear vacuoles. They expressed muscle-specific actin (8/9), smooth muscle actin (7/9), and desmin (10/12). Follow-up information was available on nine patients. All had surgery, with radiation and/or chemotherapy in seven. Three (27%) recurred at 6-24 months; in one case twice. Five (56%) had metastases, including the three with prior recurrences at 1-128 months. Five (including two who received adjuvant therapy) were disease-free at a median of 47 months, one was alive with metastatic disease at 24 months), and three were dead of disease (median 13 months).

CONCLUSIONS

Head and neck leiomyosarcomas are rare and aggressive neoplasms which metastasize. Adjuvant therapy has limited effect.

Tyrosine kinase oncogenes in normal hematopoiesis and hematological disease

Tyrosine kinase oncogenes are formed as a result of mutations that induce constitutive kinase activity. Many of these tyrosine kinase oncogenes that are derived from genes, such as c-Abl, c-Fes, Flt3, c-Fms, c-Kit and PDGFRbeta, that are normally involved in the regulation of hematopoiesis or hematopoietic cell function. Despite differences in structure, normal function, and subcellular location, many of the tyrosine kinase oncogenes signal through the same pathways, and typically enhance proliferation and prolong viability. They represent excellent potential drug targets, and it is likely that additional mutations will be identified in other kinases, their immediate downstream targets, or in proteins regulating their function.

Inflammatory myofibroblastic tumors (inflammatory pseudotumors) of the gastrointestinal tract: how closely are they related to inflammatory fibroid polyps?

Inflammatory myofibroblastic tumors (inflammatory pseudotumors) and inflammatory fibroid polyps of the gastrointestinal tract both feature prominent inflammatory infiltrates admixed with spindle-shaped fibroblasts/myofibroblasts set in a collagenous, fibrovascular, or myxoid stroma. Erroneously, some have considered inflammatory fibroid polyps to be intraluminal manifestations of inflammatory myofibroblastic tumors. In this study, we have characterized the histopathology of inflammatory myofibroblastic tumors, tumors that have only rarely been reported in the gastrointestinal tract, and have focused on whether inflammatory myofibroblastic tumors and inflammatory fibroid polyps in the gastrointestinal tract are distinct or similar. Clinical, histopathologic, and immunohistochemical features of 38 inflammatory myofibroblastic tumors limited to the wall of the gastrointestinal tract were compared with those of 45 inflammatory fibroid polyps. Compared to patients with inflammatory fibroid polyps, those with inflammatory myofibroblastic tumors were younger (mean age 41 years vs. 53 years); had larger tumors (mean 8 +/- 5.2 cm vs. 3.6 +/- 4.6 cm); presented with abdominal pain, fever, and weight loss more frequently and less frequently had bowel obstruction. Inflammatory fibroid polyps had more eosinophils and fibrosis and fewer lymphoid cell infiltrates than inflammatory myofibroblastic tumors. A regular vascular pattern was a feature of inflammatory fibroid polyps but not of inflammatory myofibroblastic tumors. Most (82%) inflammatory fibroid polyps were positive for CD34 versus none of the inflammatory myofibroblastic tumors. Smooth muscle actin was more frequently positive in inflammatory myofibroblastic tumors than in inflammatory fibroid polyps (86% versus 13%). Inflammatory myofibroblastic tumors were much less frequent and were more evenly distributed in the gastrointestinal tract than inflammatory fibroid polyps. Both appear to be benign processes. Inflammatory myofibroblastic tumors, but not inflammatory fibroid polyps, had a tendency to recur. In conclusion, inflammatory myofibroblastic tumors of the gastrointestinal tract are extremely rare and differ clinically, histologically, and immunohistochemically from inflammatory fibroid polyps.

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.