TFE3 rearranged epithelioid hemangioendothelioma of bone: A clinicopathological,immunohistochemical and molecular study of two cases

Epithelioid hemangioendothelioma (EHE) is a rare malignant angiocentric vascular neoplasm. Around 90% of classic EHE has a t(1;3)(p36;q25) that results in a WWTR1-CAMTA1 fusion gene, a histologically distinctive subset of EHE has been recently shown to have a t(10;14)(p13;q42)that results in a different fusion gene, YAP1-TFE3. Twenty-one cases of TFE3 Rearranged Epithelioid Hemangioendothelioma have been reported in the literature, and only two cases occurred in bone. In the report, we report additional two cases occurred in the femur and skull and review the related literature.     

Variant WWTR1 gene fusions in epithelioid hemangioendothelioma—A genetic subset associated with cardiac involvement

The genetic hallmark of epithelioid hemangioendothelioma (EHE) is a recurrent WWTR1‐CAMTA1 fusion, which is present in most cases bearing a conventional histology. A subset of cases is characterized by a distinct morphology and harbors instead of YAP1‐TFE3 fusion. Nevertheless, isolated cases lack these canonical fusions and remain difficult to classify. Triggered by an index case of a left atrial mass in a 76‐year‐old female with morphologic features typical of EHE, but which showed a WWTR1‐MAML2 fusion by targeted RNA sequencing, we searched our files for similar cases displaying alternative WWTR1 fusions. A total of 6 EHE cases were identified with variant WWTR1 fusions, four of them presenting within the heart. There were three females and three males, with a wide age range at diagnosis (21‐76 years, mean 62, median 69). The four cardiac cases occurred in older adults (mean age of 72, equal gender distribution); three involved the left atrium and one the right ventricle. One case presented in the vertebral bone and one in pelvic soft tissue. Microscopically, all tumors had morphologic features within the spectrum of classic EHE; two of the cases appeared overtly malignant. All cases were tested by FISH and four were investigated by targeted RNA sequencing. Two tumors harbored WWTR1‐MAML2 fusions, one WWTR1‐ACTL6A, and in three cases, no WWTR1 partner was identified. Of the four patients with follow‐up, two died of disease, one was alive with lung metastases, and the only patient free of disease was s/p resection of a T11 vertebral mass. Our findings report on additional genetic variants involving WWTR1 rearrangements, with WWTR1‐MAML2 being a recurrent event, in a small subset of EHE, which appears to have predilection for the heart.     

Malignant pleuropulmonary epithelioid hemangioendothelioma – Unusual presentation of an aggressive angiogenic neoplasm

Epithelioid hemangioendothelioma (EHE) of the lung and pleura are rare tumors. Primary pleural EHE are associated with aggressive behavior and poor clinical outcome. Recent advances in EHE include the development of immunohistochemical markers of vascular differentiation, namely Fli-1, and the identification of a specific chromosomal translocation (t(1;3)(p36;q25)). We present a 19 year old male patient with a rapidly progressive malignant neoplasm that presented as a multinodular lung parenchymal process, with associated pleural effusion and thickening. Pathologic examination revealed a pleuropulmonary neoplasm with cytologic features including round to oval epithelioid cells with frequent cytoplasmic vacuoles. Immunohistochemistry confirmed vascular differentiation of tumor cells (CD34, CD31 and Fli-1 positive). While the cytologic features were suggestive of EHE, the aggressive nature of the neoplasm, with disseminated pleuropulmonary involvement, raised the question of whether the neoplasm should be classified as EHE or epithelioid angiosarcoma. Here, we review the clinicopathologic characteristics of pleuropulmonary EHE and the overlap between malignant EHE and angiosarcoma.     

Identification of breakpoint cluster regions at 1p36.3 and 3q21 in hematologic malignancies with t(1;3)(p36;q21)

The reciprocal translocation t(1;3)(p36;q21) is associated with myelodysplastic syndromes (MDSs) and acute myeloid leukemia (AML) characterized by trilineage dysplasia, in particular dysmegakaryocytopoiesis, and a poor prognosis. As yet no molecular genetic analyses of the t(1;3) have been reported. In four patients with t(1;3), all of whom had AML-M4, which evolved from MDS, the breakpoints at 3q21 clustered within a 60-kb region centromeric to the breakpoint of the inv(3)(q21q26), whereas the breakpoints at 1p36 clustered within a 90-kb region at 1p36.3. The presence of novel clusters in both the 3q21 and 1p36 breakpoints (BCRs) suggests a common, underlying molecular mechanism for the development of t(1;3)-positive MDS/AML. The Ribophorin I (RPN1) gene close to the BCR at 3q21 was highly expressed without gross structural changes, whereas the GR6 gene located within the BCR at 3q21 was not expressed. No other highly expressed genes were isolated in a 150-kb region at 3q21. Thus, it is likely that a gene at 1p36.3 is activated by the translocation of the 3q21 region or a gene important for transformation lies on 3q21, outside the 150-kb region. Further characterization of the BCRs at 1p36.3 and 3q21 should provide important insights into the molecular genetic mechanisms involved in the genesis of t(1;3)-positive MDS/AML. Genes Chromosomes Cancer 27:229-238, 2000.     

An ins(X;11)(q24;q23) fuses the MLL and the Septin 6/KIAA0128 gene in an infant with AML-M2

The MLL (HRX, ALL-1 HTRX) gene at chromosome band 11q23 frequently is rearranged in acute lymphoblastic and myeloblastic leukemia. To date, more than 40 different 11q23 abnormalities have been described on the cytogenetic level, and at least 25 of the respective fusion partner genes are cloned. The vast majority of the respective reciprocal translocations generate a chimeric 5'-MLL/partner-3' gene on the derivative 11q23. In this work, we report a unique ins(X;11)(q24;q23) in an infant with acute myeloid leukemia (AML-M2) that fuses the human KIAA0128 gene at Xq24 with MLL. In contrast to the typical reciprocal MLL translocations, however, we provide evidence that the 5'-MLL/KIAA0128-3' fusion resides on Xq24 rather than on 11q23. The KIAA0128 gene encodes the human Septin 6 protein, which contains an ATP-GTP binding motif and three nuclear targeting sequences in its carboxy terminus. The maintenance of the reading frame of the 5'-MLL/KIAA0128-3' mRNA fusion allows for the formation of a novel chimeric protein. Septin 6 is the third member of the Septins that is fused to the MLL protein; the other two are hCDCrel at 22q11 and MSF at 17q25.     

A fluorescence in situ hybridization study of ETV6-NTRK3 fusion gene in secretory breast carcinoma

The translocation t(12;15)(p13;q25), in which the ETV6 gene from chromosome 12 is rearranged with the NTRK3 gene from chromosome 15, has recently been identified in secretory breast carcinoma (SBC). This fusion gene was initially described in congenital fibrosarcoma and congenital mesoblastic nephroma. The biological consequence of this translocation is the expression of a chimeric protein tyrosine kinase with potent transforming activity. To assess the frequency of t(12;15)(p13;q25) in breast cancer, we developed complementary probe sets (fusion and split-apart probes) for the detection of this translocation by fluorescence in situ hybridization (FISH) in paraffin-embedded, formalin-fixed tissue sections. We tested four histologically confirmed cases of SBC for the presence of the ETV6-NTRK3 gene fusion and then applied the FISH assay to tissue microarrays (TMAs) in order to screen 481 cases of formalin-fixed, paraffin-embedded invasive breast carcinomas of various histologic subtypes. Three of the four cases of SBC revealed fusion signals. Of the 481 cases in the TMAs, 202 gave signals of sufficient quality for screening by FISH, and only one case showed fusion signals in most or all of the tumor cells. On review of the histology of this case, SBC was confirmed. On the other hand, none of the fusion-negative breast cancers revealed SBC histology. In all cases, the results from the fusion and split-apart FISH assays for the ETV6-NTRK3 fusion genes were concordant. Our data suggest that the ETV6-NTRK3 fusion gene is a specific genetic alteration in SBC.