Helen Lawce

Demonstration of Philadelphia chromosome negative abnormal clones in patients with chronic myelogenous leukemia during major cytogenetic responses induced by imatinib mesylate

Imatinib mesylate, an Abl-specific kinase inhibitor, produces sustained complete hematologic responses (CHR) and major cytogenetic responses (MCR) in chronic myeloid leukemia (CML) patients, but long-term outcomes in these patients are not yet known. This article reports the identification of clonal abnormalities in cells lacking detectable Philadelphia (Ph) chromosome/BCR–ABL rearrangements from seven patients with chronic- or accelerated-phase CML, who were treated with imatinib. All seven patients were refractory or intolerant to interferon therapy. Six of seven patients demonstrated MCR and one patient, who had a cryptic translocation, achieved low-level positivity (2.5%) for BCR–ABL by fluorescence in situ hybridization. The median duration of imatinib treatment before the identification of cytogenetic abnormalities in BCR–ABL-negative cells was 13 months. The most common cytogenetic abnormality was trisomy 8, documented in three patients. All patients had varying degrees of dysplastic morphologic abnormalities. One patient exhibited increased numbers of marrow blasts, yet consistently demonstrated no Ph-positive metaphases and the absence of morphologic features of CML. The presence of clonal abnormalities in Ph-negative cells of imatinib-treated CML patients with MCR and CHR highlights the importance of routine metaphase cytogenetic testing and long-term follow-up of all imatinib-treated patients.

SNRPN methylation patterns in germ cell tumors as a reflection of primordial germ cell development

Studies examining altered imprinted gene expression in cancer compare the observed expression pattern to the normal expression pattern for a given tissue of origin, usually the somatic expression pattern for the imprinted gene. Germ cell tumors (GCTs), however, require a developmental stage‐dependent comparison. To explore using methylation as an indicator of germ cell development, we determined the pattern of methylation at the 5′ untranslated region of SNRPN in 89 GCTs from both children and adults. Fifty‐one of 84 tumors (60.7%) (12/30 (40%) of cultured pediatric GCTs, 23/36 (63.9%) of frozen adult GCTs, and 16/23 (69.5%) of frozen pediatric GCTs, with five samples having results from both cultured and uncultured material) demonstrated a nonsomatic methylation pattern after dual digestion with XbaI, NotI, and Southern blot analysis. In contrast, only 2 of 18 (11%) control samples (16 non‐GCTs and 2 normal ovaries) exhibited a nonsomatic pattern. In both cases, the result was shown to be due to copy number differences between maternal and paternal homologs, unlike the GCTs in which there was no evidence of an uneven homolog number. A comparison of the data for only the gonadal GCTs and the control data showed a highly significant difference in the proportion of tumors with methylation alterations at this locus (P = 0.0000539). Since there is no published evidence of the involvement of SNRPN methylation changes in the development of malignancy, the data suggest that the methylation pattern of SNRPN in GCTs reflects that of the primordial germ cell giving rise to the tumor.

Evaluation of Her-2/neu Status in Carcinomas With Amplified Chromosome 17 Centromere Locus

Accurate assessment of Her-2/neu (erb-b2) status in breast carcinoma is essential for therapy planning. Clinical assays are targeted at protein overexpression (immunohistochemical analysis) or gene amplification (fluorescence in situ hybridization [FISH]). Cases with aberrant FISH signal patterns are problematic and may lead to underreporting of Her-2/neu amplification. We performed FISH with additional chromosome 17 probes, SMS (Smith-Magenis syndrome critical region) and RARA (retinoic acid receptor), on 7 cases with unusual Her-2/CEP17 (chromosome 17 centromere control probe) results to assess whether different measurements of chromosome 17 copy number might clarify the Her-2/neu amplicon status. Although the Her-2/CEP17 ratio scores were within normal range (<2.0), the Her-2/SMS or Her-2/RARA ratio revealed amplification of Her-2/neu in 5 of 7 cases. Immunohistochemical analysis demonstrated Her-2/neu protein overexpression in the same 5 cases only. We describe novel application of SMS/RARA FISH probes for assessing cases with complex Her-2/CEP17 FISH patterns. Such additional data, correlated with immunohistochemical analysis, may help guide therapy in patients with breast carcinoma.

Complex translocation (7;22) identified in an epithelioid hemangioendothelioma

We describe a malignant epithelioid hemangioendothelioma arising in the back of a 45-year-old man with pulmonary and bone marrow metastases. Light microscopic and immunohistochemical features of this tumor are presented. Karyotyping revealed several clonal abnormalities: a complex unbalanced translocation [7;22] involving multiple breakpoints (confirmed by fluorescence in situ hybridization), a Robertsonian t(14;14), and loss of the Y chromosome. Monosomy for chromosome 11 was noted in a subset of the tumor cells. To our knowledge a karyotype has not been previously reported for this unusual vascular tumor.

The New Equivocal: Changes to HER2 FISH Results When Applying the 2013 ASCO/CAP Guidelines.

OBJECTIVES Human epidermal growth factor receptor 2 (HER2, ERBB2) testing is an important prognostic/predictive marker in breast cancer management, especially in selecting HER2-targeted treatment. American Society of Clinical Oncology (ASCO)/College of American Pathologists (CAP) guidelines address HER2 status and were recently revised in 2013, replacing the 2007 version. For in situ hybridization interpretation, 2013 guidelines return to the prior threshold of a HER2/CEP17 ratio of 2.0 or greater for positive and eliminate 1.8 to 2.2 as the equivocal range. Also, the HER2 signal/nucleus ratio is accounted for, with 6.0 or greater for positive and 4.0 to less than 6.0 for equivocal, even in cases with a HER2/CEP17 ratio less than 2.0. METHODS With institutional review board approval, we reviewed our 2006 to 2012 HER2 fluorescence in situ hybridization (FISH) results and classified them according to both the 2007 and 2013 guidelines as negative, positive, or equivocal. RESULTS Of 717 HER2 FISH results, 55 (7.7%) changed category when reassessed by 2013 guidelines. Nineteen of 25 results in the 2007 equivocal category were reassigned as positive (n = 13) or negative (n = 6). Thirty-five previously negative cases became equivocal in the 2013 scheme, 12 of these with 1+ immunohistochemistry. The positive category increased from 71 to 85. CONCLUSIONS The 2013 ASCO/CAP guidelines increased the number of HER2 FISH positive and equivocal results. The equivocal group is substantially different, posing a dilemma for clinical management.

Cytogenetic analysis of a hemosiderotic fibrolipomatous tumor

Hemosiderotic fibrolipomatous tumor is an extremely rare, nonencapsulated, fatty lesion with a consistent histologic appearance that was originally considered reactive in nature. To our knowledge, there are no previous reports on the cytogenetics of this lesion. Reported here is a case of hemosiderotic fibrolipomatous tumor arising within the subcutaneous tissue of the right foot, dorsal aspect, of an otherwise healthy 35-year-old woman. Subsequent cytogenetic analysis revealed a clonal reciprocal translocation between chromosomes 1 and 10, with a further rearrangement involving this derivative chromosome 1 and chromosome 3. This, in addition to its characteristic morphology and immunophenotype, supports the neoplastic nature of this tumor and may aid in its diagnosis.

Clinical outcomes of four patients with microdeletion in the long arm of chromosome 2

We present clinical outcome, through several years of follow-up, of 4 mentally retarded patients, each with a small interstitial deletion in the long arm of chromosome 2, within a region on which clinical reports are infrequent. Our patient 1 was found to have del(2)(q22.3q23.3); patients 2 and 3, del(2)(q23.3q24.2); and patient 4, del(2) (q24.2q31). By comparison of our cases with each other and with those previously published with comparable interstitial deletion, we attempted to identify characteristic clinical findings. Short neck with excessive cervical skin was seen with monosomy of chromosome 2 bands q22.3-q23.3, while hypertrichosis and a peculiar high pitched cry were seen with monosomy of chromosome 2 bands q23.3-q24.2. As suggested by Moller et al. [1984: Hum Genet 68:77-86], a cleft between the first and second toes was seen with monosomy of chromosome 2 bands q24.2-q31. In addition, seizure disorder was present in patients 1 and 4 (with the more proximal and distal deletions, respectively).

Chromosomes 1 and 12 abnormalities in pediatric germ cell tumors by interphase fluorescence in situ hybridization

Chromosome studies of pediatric germ cell tumors (GCTs) show differences in abnormalities dependent on age, sex, tumor location, and histology. Previous studies suggest that loss of 1p is associated with a malignant phenotype, while amplification of 12p, a common finding in adult testicular GCTs, is uncommon in pediatric GCTs. Fifty-three pediatric GCTs were analyzed for 1p36 loss and 12p amplification by G-banding and dual-color interphase FISH with probes for the centromere and short arm of chromosomes 1 or 12. Twelve tumors with loss of 1p36 were identified. No deletion was detected in tumors with nonmalignant histology, such that there was a significant association of 1p loss with malignancy in these tumors (P = 0.00115). Five of 18 tumors from male patients had amplification of 12p, consistent with G-band results. Combined analysis of our data with those in the literature revealed a significant correlation of 12p amplification with patient age (P = 0.000196). Amplification of 12p was only seen in one of 35 tumors from female patients. Five female GCTs had numerical abnormalities of chromosome 12, and two tumors showed complete lack of 12p. This spectrum of abnormalities differs from what is seen in the male tumors, providing further evidence for different etiologies of GCTs between the sexes.

Chromosome analysis guidelines preliminary report

These guidelines have been developed by the Association of Cytogenetic Technologists (ACT) for chromosome analysis. In formulating its recommendations, the task force reviewed guidelines established by several states and regional genetics groups. Draft guidelines prepared by the task force were reviewed by a panel of expert consultants, all of whom are laboratory directors and well known in their respective fields of expertise. The intention of the task force was to reflect procedures that are believed to be generally accepted by cytogenetic laboratories as basic criteria for effective chromosome analysis and that are consistent with existing cytogenetic quality assurance guidelines. It is important to stress that the primary purpose of the task force at this time is to establish guidelines for chromosome analysis. While the present guidelines address issues other than chromosome analysis, they do so incidentally and only in general terms. A more comprehensive discussion of other technical aspects of cytogenetics can be found in the forthcoming second edition of the ACT Cytogenetics Laboratory Manual. It is important to note that these guidelines are not intended to prescribe appropriate analyses for all individual circumstances. That determination is appropriately a matter for the judgment of the laboratories concerned. ACT, its members, and the task force that assisted in preparation of these guidelines make no warranty and assume no liability with respect to the information contained herein.

Meiotic exchange event within the stalk region of an inverted chromosome 22 results in a recombinant chromosome with duplication of the distal long arm

Meiotic recombination occurs between homologous euchromatic regions of human chromosomes in early meiosis. However, such exchanges have been thought not to occur in the stalk regions of acrocentric chromosomes. We describe a child whose chromosome analysis suggests that crossovers do occur in homologous stalk regions. The proband, initially seen as a term female infant, was born to a 28‐year‐old mother. Dysmorphic features included wide metopic sutures, low anterior hairline, hypertelorism, external ear malformations, and cleft lip and palate. Blood chromosomes of the proband and parents were studied by G‐banding, Q‐banding, R‐banding, and silver staining. The infant karyotype showed a sub‐metacentric chromosome 22; that of the mother showed a pericentric inversion of chromosome 22. Chromosomes of the father were normal. In the infant, the abnormal chromosome 22 long arm appeared normal, but with additional long arm material attached to the distal short arm. In the mother, the distal long arm of the abnormal chromosome 22 was translocated to the distal short arm. The abnormal chromosome stalk in the child was intermediate in size to the stalk size of the abnormal and normal chromosomes 22 in the mother. Fluorescent in situ hybridization (FISH) analysis using chromosome 22 paint and ARSA gene probe confirmed that the duplicated material in the proband was of chromosome 22 origin; the karyotype interpretation is: 46,XX,rec(22)dup(22q)inv(22)(p13q13.1)mat. This abnormal karyotype is most likely due to a crossover event within the inversion loop during meiosis. The stalk length discrepancy suggests that the crossover site occurred in the stalk region.