Benhur Amanuel

Malignant gastrointestinal neuroectodermal tumor: clinicopathologic, immunohistochemical, ultrastructural, and molecular analysis of 16 cases with a reappraisal of clear cell sarcoma-like tumors of the gastrointestinal tract.

The clinical, histologic, immunophenotypic, ultrastructural, and molecular features of a distinctive gastrointestinal tumor are described. Sixteen patients, 8 women and 8 men aged 17 to 77 years (mean age, 42 y; 63% less than 40 y) presented with abdominal pain, intestinal obstruction, and an abdominal mass. Mean tumor size was 5.2 cm (range, 2.4 to 15.0 cm). The tumors arose in the small bowel (10), stomach (4), and colon (2) and were histologically characterized by a sheet-like or nested population of epithelioid or oval-to-spindle cells with small nucleoli and scattered mitoses. Five cases showed focal clearing of the cytoplasm. Scattered osteoclast-type multinucleated giant cells were present in 8 cases. The tumor cells were positive for S-100 protein, SOX10, and vimentin in 100% of cases, for CD56 in 70%, for synaptophysin in 56%, for NB84 in 50%, for NSE in 45%, and for neurofilament protein in 14% of cases. All cases tested were negative for specific melanocytic, gastrointestinal stromal tumors, epithelial, and myoid markers. Ultrastructural examination of 5 cases showed features of primitive neuroectodermal cells with clear secretory vesicles, dense-core granules, occasional gap junctions, and no evidence of melanogenesis. EWSR1 gene rearrangement was assessed by fluorescence in situ hybridization in 14 cases. Twelve cases (86%) showed split EWSR1 signal consistent with a chromosomal translocation involving EWSR1. One case showed extra intact signals, indicating that the nuclei possessed either extra copies of the EWSR1 gene or chromosome 22 polysomy. Only 1 case showed no involvement of the EWSR1 gene. Six cases demonstrated rearrangement of the partner fusion gene ATF1 (46%), and 3 showed rearrangement of CREB1 (23%); 2 cases lacked rearrangement of either partner gene. Clinical follow-up was available in 12 patients and ranged from 1.5 to 106 months. Six patients died of their tumors (mean survival, 32 mo; 83% less than 24 mo). At last follow-up, 4 patients were alive with regional, lymph node, and liver metastases, and 2 patients were alive with no evidence of disease. The tumor described here is an aggressive form of neuroectodermal tumor that should be separated from other primitive epithelioid and spindle cell tumors of the gastrointestinal tract. The distinctive ultrastructural features and absence of melanocytic differentiation serve to separate them from soft tissue clear cell sarcomas involving the gastrointestinal tract. The designation “malignant gastrointestinal neuroectodermal tumor” is proposed for this tumor type.

Incidence of BRAF p.Val600Glu and p.Val600Lys mutations in a consecutive series of 183 metastatic melanoma patients from a high incidence region

Aim: Approximately 40–60% of melanomas from Caucasian populations carry activating mutations in the BRAF oncogene, with the most common being the p.Val600Glu (V600E) hotspot mutation in exon 15. The aim of the present study was to investigate the frequency of the less common p.Val600Lys (V600K) mutation in metastatic melanoma from a high incidence region. Method: Dideoxy sequencing and fluorescent single strand conformation analysis were used to screen for mutations in exon 15 of BRAF in 183 cases of metastatic melanoma. Results: The overall incidence of BRAF mutation (89/183, 49%) was very similar to other large studies of Caucasian populations. However, the frequency of the p.Val600Lys mutation was higher than in most other studies and comprised almost one-third of all BRAF mutations in our cohort (27/89, 30%). Conclusion: BRAF p.Val600Lys mutations were present at a relatively high frequency in this cohort of metastatic melanoma patients (27/183, 15%). Assays used to screen for BRAF mutations in the clinic should be robust enough to detect the p.Val600Lys mutation, as this may have therapeutic implications.

Microsatellite instability in colorectal cancer.

Approximately 20 percent of right‐sided colon cancers and 5 percent of left‐sided colon and rectal cancers have a deficient DNA mismatch repair system. This results in the widespread accumulation of mutations to nucleotide repeats, some of which occur within the coding regions of cancer‐related genes such as TGFβRII and BAX. A standardized definition for microsatellite instability (MSI) based on the presence of deletions to mononucleotide repeats is gaining widespread acceptance in both research and the clinic. Colorectal cancer (CRC) with MSI are characterized histologically by an abundance of tumor‐infiltrating lymphocytes, poor differentiation and a signet ring or mucinous phenotype. In younger patients these tumors usually develop along the chromosomal instability pathway, in which case the mismatch repair genes are inactivated by germline mutation, somatic mutation and loss of heterozygosity. In older patients MSI CRC usually develops against a background of widespread hypermethylation that includes methylation‐induced silencing of the mismatch repair gene MLH1. The overall biological and clinical phenotype of MSI CRC that arise in these two pathways is likely to be different and may account for some of the discordant results reported in the literature relating to the clinical properties of these tumors. The available evidence indicates that MSI is unlikely to be a clinically useful marker for the prognostic stratification of early‐stage CRC. The predictive value of MSI for response to 5‐fluorouracil‐based chemotherapy remains controversial, while for other agents the predictive value is difficult to assess because they are used in combination regimens. The MSI phenotype is being actively investigated for novel therapeutic approaches based on the principle of synthetic lethality. Finally, the MSI status of CRC is an extremely useful marker for population‐based screening programs that aim to identify individuals and families with the hereditary cancer condition known as Lynch syndrome.

Superficial cervico-vaginal myofibroblastoma: a report of five cases

Aims: To describe the pathological and immunohistochemical features of five cases of superficial cervico‐vaginal myofibroblastoma (SCVM), a recently described mesenchymal tumour affecting middle‐aged and elderly females. Methods: The histological features of five cases of SCVM arising in four patients were reviewed including one case which recurred locally 9 years after initial excision biopsy. All cases were immunostained using the streptavidin‐biotin technique using antisera to vimentin, smooth muscle actin, desmin, S100 protein, cytokeratin, h‐caldesmon, calponin, CD99, CD117 (c‐kit), bcl‐2, oestrogen receptor and progesterone receptor. Results: The patients were aged from 40 to 71 years (mean 55.2 years). The tumours were situated within the vagina (four cases) and cervix (one case) and ranged from 16 to 45mm in greatest dimension. One patient had two separate vaginal SCVM. The tumours were characterised by uniform spindle and stellate‐shaped cells separated by a collagenous or myxoid stroma. No mitotic activity was identified. Characteristically the tumours were well circumscribed and separated from the surface epithelium by a rim of normal stroma. The initial and recurrent tumours in one patient were similar except for increased stromal collagen in the recurrence. All tumours were immunoreactive for vimentin, desmin, CD34, CD99, bcl‐2, calponin and hormone receptors while two tumours showed focal smooth muscle actin expression. There was no expression of S100 protein, hcaldesmon, CD117 or cytokeratin. Conclusions: SCVM appears to be a relatively distinct lesion although there is some histological and immunophenotypical overlap with other mesenchymal tumours, particularly fibroepithelial polyp, leiomyoma and solitary fibrous tumour. As local recurrence developed 9 years after intial treatment in one patient, long‐term clinical follow‐up would seem appropriate.

A multisite blinded study for the detection of BRAF mutations in formalin-fixed, paraffin-embedded malignant melanoma

Melanoma patients with BRAF mutations respond to treatment with vemurafenib, thus creating a need for accurate testing of BRAF mutation status. We carried out a blinded study to evaluate various BRAF mutation testing methodologies in the clinical setting. Formalin-fixed, paraffin-embedded melanoma samples were macrodissected before screening for mutations using Sanger sequencing, single-strand conformation analysis (SSCA), high resolution melting analysis (HRM) and competitive allele-specific TaqMan® PCR (CAST-PCR). Concordance of 100% was observed between the Sanger sequencing, SSCA and HRM techniques. CAST-PCR gave rapid and accurate results for the common V600E and V600K mutations, however additional assays are required to detect rarer BRAF mutation types found in 3–4% of melanomas. HRM and SSCA followed by Sanger sequencing are effective two-step strategies for the detection of BRAF mutations in the clinical setting. CAST-PCR was useful for samples with low tumour purity and may also be a cost-effective and robust method for routine diagnostics.

Optimizing the multimodal approach to pancreatic cyst fluid diagnosis developing a volume-based triage protocol

The objective of this study was to develop a triage algorithm to optimize diagnostic yield from cytology, carcinoembryonic antigen (CEA), and v‐Ki‐ras2 Kirsten rat sarcoma viral oncogene homolog (KRAS) testing on different components of a single pancreatic cyst fluid specimen. The authors also sought to determine whether cell block supernatant was suitable for CEA and KRAS testing.

KRAS mutation and microsatellite instability in endometrial adenocarcinomas showing MELF-type myometrial invasion

Background Some uterine endometrioid adenocarcinomas exhibit a distinctive morphological phenotype characterised by the formation of microcystic, elongated and fragmented (MELF) glands. Immunohistochemical studies have suggested that MELF-type changes represent an epithelial–mesenchymal transition which has been associated with KRAS activation in various tumours. Aims To investigate the molecular characteristics of endometrial tumours showing MELF, with particular reference to the frequencies of KRAS and BRAF mutations and of microsatellite instability (MSI). Methods MSI, and KRAS and BRAF mutation status, were assessed in 33 low-grade endometrial adenocarcinomas showing MELF features and the results compared with 33 control cases exhibiting a ‘conventional’ pattern of myometrial invasion. Standard histological parameters were also reviewed. Results Tumours with a MELF pattern of myometrial invasion showed more frequent vascular invasion and focal mucinous differentiation. KRAS mutations were more frequent in MELF positive than MELF negative tumours (45% vs 30%), but this difference was not statistically significant. BRAF mutations were not identified in any of the cases. MSI was identified in 20% of cases overall but did not correlate with the MELF phenotype. Conclusions Mutations in KRAS and BRAF genes are not directly implicated in the development of a MELF pattern of invasion in endometrial carcinoma. However, RAS-associated signalling pathways could be activated through other genetic or epigenetic mechanisms. The characterisation of such alterations may become increasingly important as novel therapies are developed that target mediators involved in tumour invasion.

Population-based screening for Lynch syndrome in Western Australia

We showed earlier that routine screening for microsatellite instability (MSI) and loss of mismatch repair (MMR) protein expression in colorectal cancer (CRC) led to the identification of previously unrecognized cases of Lynch syndrome (LS). We report here the results of screening for LS in Western Australia (WA) during 1994–2012. Immunohistochemistry (IHC) for loss of MMR protein expression was performed in routine pathology laboratories, while MSI was detected in a reference molecular pathology laboratory. Information on germline mutations in MMR genes was obtained from the states single familial cancer registry. Prior to the introduction of routine laboratory‐based screening, an average of 2–3 cases of LS were diagnosed each year amongst WA CRC patients. Following the implementation of IHC and/or MSI screening for all younger (<60 years) CRC patients, this has increased to an average of 8 LS cases diagnosed annually. Based on our experience in WA, we propose three key elements for successful population‐based screening of LS. First, for all younger CRC patients, reflex IHC testing should be carried out in accredited pathology services with ongoing quality control. Second, a state‐ or region‐wide reference laboratory for MSI testing should be established to confirm abnormal or suspicious IHC test results and to exclude sporadic cases by carrying out BRAF mutation or MLH1 methylation testing. Finally, a state or regional LS coordinator is essential to ensure that all appropriate cases identified by laboratory testing are referred to and attend a Familial Cancer Clinic for follow‐up and germline testing.

Role of endobronchial ultrasound in diagnosis and molecular assessment of metastatic melanoma

Background and objective:  Vemurafenib is a new inhibitor of the mutated BRAF oncogene. In the presence of mutated BRAF in metastatic melanoma, treatment with vemurafenib leads to a reduction in mortality and in tumour progression when compared with chemotherapy. This study describes nine cases in which endobronchial ultrasound (EBUS) guided transbronchial needle aspiration (TBNA) was used to assess mediastinal and hilar lymph nodes for the presence of metastatic melanoma and demonstrates the ability to detect mutations in BRAF on the tissue obtained.

Equivocal ALK fluorescence in-situ hybridization (FISH) cases may benefit from ancillary ALK FISH probe testing.

Accurate assessment of anaplastic lymphoma kinase (ALK) gene rearrangement in non‐small‐cell lung cancers (NSCLCs) is critical to identify patients who are likely to respond to crizotinib. The aim of this study was to evaluate the ALK/EML4 TriCheck FISH probe in a series of NSCLCs enriched for tumours with equivocal ALK status.