NRASQ61R Mutation-specific Immunohistochemistry is Highly Specific for Either NRASQ61R or KRASQ61R Mutation in Colorectal Carcinoma.

Anti-epidermal growth factor receptor-targeted therapy is only indicated in RAS wild-type colorectal carcinomas (CRCs). It is recommended that both NRAS and KRAS mutation testing to be performed before a CRC is considered RAS wild-type. Given that mutation-specific immunohistochemistry (IHC) has been shown to be sensitive and specific for the detection of NRAS mutations in melanoma, we assessed the specificity of NRAS mutation-specific IHC in CRC. IHC was performed on tissue microarrays containing 2823 consecutive CRC undergoing surgery with curative intent using a novel mutation-specific antibody to the protein produced by the NRAS mutation (clone SP174). Tissue microarrays were assessed by 2 observers and all IHC-positive or equivocal cases were repeated on whole sections to confirm the result. Positive cases then underwent molecular testing by matrix-assisted laser desorption/ionization-time of flight polymerase chain reaction. In total, 22 of 2823 (0.8%) CRCs demonstrated confirmed positive staining with complete interobserver concordance. RAS mutations were confirmed in all IHC-positive CRCs. In total, 11 cases harbored the NRASQ61R mutation. Surprisingly, 11 cases demonstrated the KRASQ61R mutation. We conclude that mutation-specific IHC with this currently available NRASQ61R antibody is highly specific for the presence of either NRASQ61R or KRASQ61R mutations in CRC. We caution that we did not assess the sensitivity of IHC and that this antibody does not detect other RAS mutations. Therefore, negative staining does not exclude a clinically significant RAS mutation. However, positive staining confirms the presence of an NRASQ61R or KRASQ61R mutation without the need for further molecular testing.

NRASQ61R Mutation-specific Immunohistochemistry Also Identifies the HRASQ61R Mutation in Medullary Thyroid Cancer and May Have a Role in Triaging Genetic Testing for MEN2.

A quarter of patients with medullary thyroid carcinoma (MTC) have germline mutations in the RET proto-oncogene indicating MEN2. Therefore genetic testing is recommended for all patients presenting with MTC. Approximately 40% of MTCs have somatic RET mutations. Somatic mutations in the RAS genes are the next most common driver mutations and appear to be mutually exclusive with germline RET mutation. The single most common somatic RAS mutation is HRASQ61R (c.182A>G), reported in 4.6% to 11% of all MTCs. Mutation-specific immunohistochemistry (IHC) initially developed to identify the NRASQ61R mutation in melanoma (clone SP174) has proven highly sensitive and specific. Because the amino acid sequences for the HRAS and NRAS proteins at codon 61 are identical, we postulated that SP174 IHC would also identify the somatic HRASQ61R mutation. IHC with SP174 was performed on a tissue microarray of 68 patients with MTC including 13 (22.8%) with molecularly confirmed MEN2. Seven (10.3%) MTCs demonstrated positive staining. Six of these patients had already undergone germline RET mutation testing as part of clinical care and were all confirmed to be wild type, excluding the diagnosis of MEN2. All SP174 immunohistochemically positive MTCs were proven to have HRASQ61R mutation (and lack KRASQ61R and NRASQ61R) by Sanger sequencing. All MEN2 patients showed negative staining. We conclude that IHC with SP174 is highly specific for the HRASQ61R mutation in MTC. Because current data suggest that this mutation is mutually exclusive with germline RET mutation, IHC may also have a role in triaging formal genetic testing for MEN2.

USP6 gene rearrangement in nodular fasciitis and histological mimics.

AIMS: Nodular fasciitis is known to be a benign mimic of sarcoma, both clinically and histologically. Accurate diagnosis, particularly on small biopsies, remains a challenge, as the morphology can be varied and the immunophenotype is essentially non-specific. Recently, rearrangement of the ubiquitin-specific protease 6 (USP6) gene has been reported as a recurrent and specific finding in nodular fasciitis. The aim of this this study was to evaluate the diagnostic utility of USP6 fluorescence in-situ hybridization (FISH) analysis in a subset of spindle-cell proliferations in which nodular fasciitis enters into the differential diagnosis. METHODS AND RESULTS: A database search was performed at the Middlemore Hospital Histopathology Department. All in-house cases diagnosed between 2002 and March 2014 in which nodular fasciitis was considered as a differential diagnosis were retrospectively identified. Twenty cases were retrieved, reviewed and categorized as 'definite', 'possible' or 'definitely not' nodular fasciitis by consensus morphological opinion of three experienced pathologists. FISH analysis for USP6 rearrangement was performed in each case, with a commercially available break-apart probe. Of seven cases that were morphologically categorized as 'definite' nodular fasciitis, six were FISH-positive and one was FISH-negative. Of four cases categorized as 'possible' nodular fasciitis, one was FISH-positive and three were FISH-negative. Nine cases categorized as 'definitely not' nodular fasciitis were all FISH-negative. In the morphologically definitive cases, FISH analysis for USP6 had a sensitivity of 86% and specificity of 100% for a diagnosis of nodular fasciitis. The positive predictive value was 100%, and the negative predictive value 90%. CONCLUSIONS: USP6 FISH is a useful ancillary test in cases where nodular fasciitis is a potential diagnostic consideration.

Analysis of molecular cytogenetic changes in metastatic renal cell carcinoma in the setting of everolimus treatment: a pilot project.

BACKGROUND: The mTOR inhibitors have improved outcomes for patients with metastatic renal cell carcinoma (mRCC) but the duration of benefit is variable. Currently there are no predictive biomarkers for preselecting patients who are more likely to benefit from these agents. We undertook an exploratory translational study evaluating molecular cytogenetic changes in the context of outcomes from treatment with everolimus. PATIENTS AND METHODS: Ten patients with clear cell mRCC treated with everolimus were enrolled. Pretreatment tissue specimens were analyzed for molecular cytogenetic changes using fluorescence in situ hybridization and progression-free survival (PFS) data were obtained. Gene probes chosen for this analysis were: Von Hippel Lindau, fragile histidine triad, fibroblast growth factor receptor (FGFR) 1, FGFR3, PDGFß, PDGFRß, epidermal growth factor receptor, and myelocytomatosis viral oncogene. RESULTS: Median PFS was 8.75 months. Two patients with the longest PFS (28 months and 23 months) had gain of PDGFß and PDGFRß. This was also observed in 3 other patients who had a PFS of 11.5 months, 8 months, and 5.5 months, respectively. Cytogenetic evolution was observed between primary and metastatic specimens. CONCLUSION: PDGFß and PDGFRß gene status might be of relevance to everolimus therapy. Further research evaluating the utility of these potential biomarkers is required.

Differentiation between malignant melanoma and Spitz tumour has improved over the past decade due to modern pathological techniques.

A 10-year-old boy was diagnosed with a thick neurotropic melanoma of the lip in 2002. He is alive and well without evidence of disease recurrence 10 years later. We applied modern pathologic techniques to this lesion to highlight recent advances in melanoma diagnostics.

FISH detection of PML-RARA fusion in ins(15;17) acute promyelocytic leukaemia depends on probe size.

The diagnosis of acute promyelocytic leukaemia (APL) is usually confirmed by cytogenetics showing the characteristic t(15;17), but a minority of patients have a masked PML/RARA fusion. We report ten patients with APL and no evidence of the t(15;17), in whom the insertion of RARA into PML could not be demonstrated by initial FISH studies using a standard dual fusion probe but was readily identified using smaller probes. Given the need for rapid diagnosis of APL, it is important to be aware of the false negative rate for large PML/RARA FISH probes in the setting of masked rearrangements.

Cervical intraepithelial neoplasia and aneusomy of TERC: assessment of liquid-based cytological preparations.

The implementation of effective screening programs has decreased the incidence and mortality of cervical carcinoma. However, single screening tests are subjective and carry a significant false-negative rate. Therefore, supplementary tests to support the Papanicolaou (PAP) smear are being developed. Human papillomavirus (HPV) testing has increased the specificity of the PAP smear, but has high sensitivity rate. This has proven unhelpful in low-grade lesions and in young women. Cervical carcinogenesis is a multifactorial disorder. In addition to exposure to oncogenic HPV, which is regarded as the initiator, there must be a promoter to eventuate in invasive disease. The promoter factor appears to be the acquisition of extra copies of chromosome 3q and has been shown to be a constant recurrence in cervical carcinoma (squamous and adenocarcinomas). The 3q region contains the RNA sequence of the human telomerase gene TERC. Recent studies have shown a strong correlation between high-grade cervical lesions and abnormalities of TERC. This study supports the previous studies and examines the status of the TERC gene in low and high-grade cervical intraepithelial lesions, diagnosed on cytology. ASC-H smears are also examined in an attempt to categorize lesions that are more likely to progress. Potentially this may help identify women in need of close clinical follow-up and early treatment.

AIDS-related plasmablastic lymphoma of the oral cavity associated with an IGH/MYC translocation--treatment with autologous stem-cell transplantation in a patient with severe haemophilia-A.

Plasmablastic lymphoma is an AIDS related lymphoma that continues to have a poor prognosis despite significant advances in the management of HIV and lymphoproliferative diseases. In part this has been due to limited insights into the biology of this disease and the molecular mechanisms of oncogenesis. To date molecular abnormalities have not been described in plasmablastic lymphoma, and its aggressive clinical behaviour has been difficult to understand. We describe the first reported cytogenetic abnormality in plasmablastic lymphoma, an IgH/MYC translocation. It is also the first description of autologous stem cell transplantation in a patient with severe haemophilia A.

Epiphyseal dysplasia and other skeletal anomalies in a patient with the 6p25 microdeletion syndrome.

The 6p25 microdeletion syndrome comprises the Axenfeld-Rieger eye anomaly in association with a characteristic facies, developmental delay, hearing loss, and organ malformations. Skeletal anomalies in the form of hemivertebrae, clubfeet, and other positional joint anomalies have also been described in some patients. We report on a patient with a 2.2-2.4 Mb terminal microdeletion of the short arm of chromosome 6 who in addition had abnormalities of the proximal femoral and humeral epiphyses. We suggest that an epiphyseal dysplasia may be an additional clinical component of the 6p25 microdeletion syndrome.

Dermatofibrosarcoma protuberans: report of a case with a variant ring chromosome and metastases following pregnancy.

BACKGROUND: The most frequent molecular abnormality observed in dermatofibrosarcoma protuberans (DFSP) is the formation of a supernumerary ring chromosome or translocation resulting in fusion of the gene encoding the alpha-chain of type 1 collagen, COL1A1 from 17q22, to the platelet-derived growth factor beta-chain, PDGFB gene from 22q13. Rare cases documenting variant ring or marker chromosomes involving regions other than 17q22 and 22q13 have been reported. Further analysis in three of these cases demonstrated the presence of the COL1A1 and PDGFB genes. METHODS: We report a further case of DFSP with a rare variant ring chromosome. The tumor appeared to undergo accelerated growth during pregnancy, then metastasized following pregnancy. We describe the clinical, histological, immunohistochemical, and cytogenetic features. RESULTS: The metastatic tumor showed a variant r(17;?) chromosome. A locus-specific probe was required to demonstrate presence of the PDGFB gene within the ring, indicating cryptic molecular rearrangement between chromosomes 17 and 22, and recombination with an unknown chromosome. CONCLUSIONS: Cryptic rearrangement of chromosomes 17 and 22 should be suspected in variant ring chromosomes and translocations. Pregnancy may contribute to accelerated growth of DFSP, and delay in surgical resection should be avoided.

Another case of interstitial del(12) involving the proposed cardio-facio-cutaneous candidate region.

Recent reports of patients with interstitial deletions involving the long arm of chromosome 12 have led to the proposal of a candidate region for the cardio-facio-cutaneous syndrome (CFCS) at (12)(q21.2q22). We now report a patient with an interstitial deletion, del(12)(q21.1q21.3) that overlaps the proposed critical region. The patient is an 11-year-old female with developmental delay. Her growth was normal but she is microcephalic with low set ears. In common with other patients with deletions in this region, she had fine, sparse head and eyebrow hair and a hyperkeratotic follicular rash, which involved her face and limbs. She does not have the diagnostic features of the CFC syndrome.

Severe musculoskeletal phenotype associated with an unbalanced t(6;10) translocation: clarification of the locus for this phenotype on distal 6p.

Larsen syndrome is a congenital condition consisting of multiple large joint dislocations associated with a distinctive facial appearance and frequently other abnormalities. The syndrome is probably genetically heterogeneous, with both dominant and recessive inheritance reported. Previously two cases have been reported where a Larsen-like syndrome was associated with unbalanced chromosomal translocations resulting in partial trisomy 1q and monosomy distal 6p. We now report a child with an unbalanced translocation resulting in a distal 6p deletion and partial trisomy 10q, who has Larsen-like features and has also severe developmental delay. A G-banded preparation revealed a karyotype 46,XX,der(6),t(6:10)(p25;q25.2) and the breakpoint at 6p25 was confirmed by FISH using YAC probes (between 6p25 at D6s477/F13A1 and 6p24 at 6WI13606). Our case provides further evidence for a Larsen-like locus at distal 6p and reduces the potential critical region.

False-positive diagnosis of trisomy 21 using fluorescence in situ hybridisation (FISH) on uncultured amniotic fluid cells.

An amniocentesis was performed on a 22-week pregnancy following the detection of foetal abnormalities on ultrasound. A rapid aneuploid screen using fluorescence in situ hybridisation on uncultured amniotic fluid cells revealed 3 signals for chromosome 21, consistent with trisomy 21. In situ metaphase cultures revealed a 46,XY normal male karyotype. These discordant results may be explained by a sub-standard batch of the commercially available probe or alternatively, a very specific variation within the sample interacting with the probe. Alternative strategies are proposed in order to safeguard against inappropriate clinical action as a consequence of discordant results.

Supernumerary marker chromosomes 5: confirmation of a critical region and resultant phenotype.

A critical region exists at 5p13 for the phenotype associated with duplication 5p. Two unrelated Polynesian children are reported with supernumerary marker chromosomes (SMCs) 5. This brings to seven the total of reported SMCs derived from chromosome 5. The phenotype is clear, and the level of mosaicism of the marker chromosomes is contributory to the clinical severity.

Prenatal diagnosis of partial tetrasomy 14: a case study.

Prenatal specimens were received from a fetus with abnormalities noted on ultrasound. A supernumerary marker chromosome (SMC) was detected: 47,XY,+mar. Fluorescence in situ hybridisation (FISH) further classified this to be partial tetrasomy for chromosome 14. We compare this finding with other cases of SMC (14) and further classify phenotype with karyotype.