Scientist in Cytogenetics — CG(ASCP) Preparation Guide Study Guide

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A marrow container and request agree on the patient's name but show different identification numbers. Pause processing, preserve the specimen under suitable conditions, and resolve the discrepancy through the laboratory's documented identification process before establishing cultures.

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A tissue sample arrives with substantial material but was placed in a preservative incompatible with living-cell culture. Recognize that tissue quantity does not restore viability; evaluate available validated testing alternatives and communicate the limitation.

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A small tissue specimen is requested for culture and molecular testing. Before fixing the entire sample, identify the viable portion needed for culture and coordinate allocation so the remaining material can support the other ordered study.

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An adherent tissue culture shows expanding colonies while a parallel suspension contains few dividing cells. Evaluate the monolayer as the more productive system for that preparation, while retaining the specimen-specific culture plan and documentation.

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A constitutional peripheral blood culture needs dividing lymphocytes. Select the validated mitogen-containing culture system and distinguish its growth-promoting role from the later mitotic inhibitor, hypotonic treatment, and fixation stages of chromosome preparation.

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Two patient cultures are being established at the same station. Handle them separately with fresh appropriate consumables, maintain visible identifiers, and close one specimen before manipulating the next to reduce microbial and cellular crossover risks.

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Several cultures using one medium lot grow poorly while comparable cultures using another lot progress normally. Preserve the observations and lot records, investigate reagent performance, and assess whether affected specimens require additional culture attempts or limitation reporting.

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A culture has many healthy cells but yields excessively condensed chromosomes after an altered arrest step. Review inhibitor exposure and the validated harvest conditions before changing the growth medium or interpreting poor band detail as a patient abnormality.

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Most metaphases remain tightly clustered despite adequate mitotic yield. Review hypotonic treatment together with fixation and slide drying, using the compact morphology as a clue rather than immediately increasing the amount of mitotic inhibitor.

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A harvest contains ample metaphases, but slides show persistent cytoplasmic material obscuring chromosome outlines. Review fixative preparation and fixation steps alongside the preceding hypotonic treatment instead of assuming the microscope alone explains the poor images.

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One slide is crowded with overlapping metaphases, while a less concentrated preparation from the same pellet shows clear individual cells. Adjust suspension density within the validated method before repeating the entire culture and harvest process.

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A suspected small rearrangement cannot be localized on short, highly condensed chromosomes. Consider a validated elongation approach or complementary molecular testing, then assess whether the resulting preparations actually provide the required regional band detail.

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Chromosomes from a normally productive harvest appear pale and poorly defined after a longer digestion step. Investigate excessive trypsin exposure and reagent conditions, then compare a preparation banded under validated conditions before assigning structural findings.

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A targeted deletion is suspected in a defined region. Choose a probe covering that region, verify that processing permits specific hybridization, and interpret the result within the probe's coverage rather than claiming a genome-wide assessment.

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An interphase assay detects an extra locus signal, but its chromosomal location remains uncertain. Use suitable metaphase FISH to determine where the additional target lies, rather than assuming that every extra signal represents an intact extra chromosome.

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Tumor nuclei show increased signals for a gene target. Compare the target pattern with the validated reference strategy before distinguishing regional amplification from a broader increase in chromosome copies affecting both the target and reference.

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Under insert 30-608495/R1, two fused pairs illustrate an intact pattern. One fused pair plus an orange–green pair three signal diameters apart is positive; one fused pair plus isolated orange is also positive. Initially score 50 evaluable cells: fewer than 5 positive is negative, more than 25 is positive, and 5–25 is equivocal. For an equivocal initial result, a second reader evaluates another 50 cells. Combine both readings over 100 cells: fewer than 15 positive is negative and at least 15 is positive. Boundary example: 5 positive cells in the first reading plus 9 in the second gives 14/100, negative; 5 plus 10 gives 15/100, positive.

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The clinical question specifically concerns BCR and ABL1 juxtaposition. Select a validated fusion strategy addressing those two targets rather than assuming a generic break-apart result at one locus establishes the same partner-specific finding.

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Both patient and control slides show weak target fluorescence after a wash-condition change, although DAPI outlines remain clear. Investigate assay processing and control performance before interpreting the patient as lacking the target sequence.

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A tissue section contains numerous small nuclear profiles with reduced target counts. Assess section-related truncation and the validated tissue scoring rules before diagnosing deletion from isolated one-signal profiles scattered across otherwise adequate tissue.

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A marrow specimen contains relatively few plasma cells among many other nucleated cells. A validated plasma cell enrichment approach can improve targeted FISH assessment, but document enrichment so the resulting abnormal-cell percentage is interpreted in context.

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Suppose specimen-matched normal data show a 2% observed background frequency and the laboratory's documented statistical analysis yields a 6% upper reference limit. These hypothetical values have different roles: 2% describes the observations; 6% is the derived decision threshold. A patient with 9 qualifying nuclei among 180 has an observed frequency of 5%. Under a prespecified rule requiring greater than 6%, that patient result does not exceed the cutoff. Near the threshold, finite sampling, specimen heterogeneity, and reader variation can change classification; assess technical quality and clinical findings, with additional scoring, independent review, or repeat testing when supported by the established assay procedure.

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A patient slide appears negative, but the positive control fails to show the expected rearrangement pattern. Investigate the failed control and withhold a definitive negative interpretation rather than relying on several visually clear patient nuclei.

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Worked comparison: an adequately covered interval shows a sustained negative log2 ratio across contiguous probes, sharp transitions to normal flanking regions, and only single-allele SNP states consistent with one copy. DNA and array QC pass, and the call exceeds the assay's validated probe and size requirements: this supports a deletion without automatic confirmation. A small putative loss supported by a few erratic probes, weak signal shift, and discordant SNP evidence falls outside validated criteria. Review raw data, coverage, DNA quality, and possible mosaicism; repeat processing or investigate independently with suitable qPCR, MLPA, FISH, or another platform before reporting it.

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An SNP array shows normal regional dosage with a long region lacking heterozygous calls. Interpret the combination as a possible copy-neutral allelic finding and evaluate its context rather than labeling it a deletion solely from homozygosity.

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Two neighboring bands remain merged after repeated digital zooming. Check optical setup, focus, and the appropriate objective before enlarging further, because a larger display of unresolved detail will not establish a defensible band boundary.

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DAPI-stained nuclei are visible, but one probe color disappears after a filter change. Check the excitation and emission configuration for that fluorophore before interpreting the missing channel as biological loss in the patient.

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A suspected small deletion appears only after extreme contrast adjustment. Review the original capture and additional metaphases, then determine whether the band difference is reproducible before including the finding in the final karyogram or report.

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One field contains sharply banded chromosomes but overlapping cells; another contains a complete, well-separated metaphase with adequate bands. Prefer the latter for full analysis because completeness and individual chromosome assignment are essential to a defensible result.

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A metaphase contains 46 chromosomes, but one homolog has an altered distal band pattern. Continue structural analysis rather than calling the cell normal from its count, and document the extent of examination performed.

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Two chromosomes look similar in length, but their centromere positions and band sequences differ. Use the combined features to assign them, then reconcile the completed karyogram with the original metaphase before accepting the arrangement.

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A breakpoint is clearly on a long arm, but adjacent sub-bands cannot be distinguished. Record the supported localization and seek better resolution or complementary testing before assigning a more detailed address unsupported by the image.

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A family history raises concern for a small regional imbalance, but available metaphases show only coarse banding. Recognize the limited exclusion power and consider an appropriately targeted or genomic dosage assay rather than promising that routine morphology excludes it.

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A complete metaphase contains 47 chromosomes, including three recognizable chromosome 21 homologs. This supports trisomy 21 rather than merely an unspecified structural change; confirm chromosome identity and assess whether the pattern recurs in the analyzed cells.

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A well-separated cell contains 69 chromosomes with three representatives of each autosome. Recognize a triploid pattern rather than multiple unrelated trisomies, then evaluate additional cells and specimen context before characterizing the overall sample.

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Targeted testing indicates three copies of a chromosome 21 locus. Review the karyotype to determine whether the additional material is a separate chromosome or part of a translocation, rather than assuming the signal count identifies the mechanism.

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One homolog appears shorter in a single poorly banded metaphase. Examine additional well-banded cells and compare the expected regional sequence before diagnosing deletion; use an appropriate complementary assay if the suspected loss remains below reliable morphological resolution.

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Microarray identifies a regional copy gain, and the karyotype shows extra material on a different chromosome. Use the findings together to investigate the gain's physical location rather than describing the array alone as proof of a tandem duplication.

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A person has a reciprocal exchange on karyotyping and no detectable array imbalance. Explain the compatible findings and preserve the structural interpretation rather than discarding the translocation because the dosage study appears normal.

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A complete metaphase contains 45 chromosomes and a large derivative representing two acrocentric long arms. Assess a Robertsonian arrangement and material balance instead of assuming that one entire chromosome's essential content is absent because the count is reduced.

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Band analysis shows a reversed segment extending from the short arm across the centromere into the long arm. Classify the arrangement as pericentric, and distinguish its altered order from a deletion or duplication of the same region.

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A chromosome has matching long-arm band patterns on both sides of its centromere, with the corresponding short-arm material absent from that chromosome. Consider an isochromosome and assess the resulting arm-level dosage across the full complement.

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Several cells contain a ring-shaped chromosome, while others show a different count. Document both structural and numerical observations, evaluate additional suitable cells, and use appropriate studies to characterize retained or lost material rather than assuming every ring is identical.

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An elongated derivative shows two convincing centromeric regions. Investigate a dicentric structure and its chromosome content rather than calling it a simple duplication based only on increased length and repeated-looking material in the captured image.

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A small extra chromosome lacks enough recognizable bands for assignment. Record the unresolved structural finding, then select complementary testing to identify its origin and content instead of assigning it to the smallest normal chromosome by appearance.

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Two reproducible chromosome complements are found in one person's specimen. Consider mosaicism, chimerism, and specimen-related explanations, using history and independent evidence rather than assuming that any mixture of cell types proves a postzygotic event.

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Assume independent sampling and a true abnormal fraction of 5%. The chance of missing it in 30 cells is 0.95 raised to 30, approximately 21.5%; zero observed abnormal cells therefore does not prove absence.

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An abnormality appears in several cells from one colony but is absent from another independently established culture. Review colony relationships and additional evidence before interpreting the cell count as proof that the abnormality broadly represents the specimen.

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A rearrangement is identified in marrow evaluated for a suspected neoplasm. Interpret it within that tissue and clinical setting, and use appropriate additional evidence if determining constitutional status is necessary rather than extending the marrow result to all tissues.

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A marrow karyotype shows a chromosome 9–22 exchange, and partner-specific testing confirms BCR::ABL1. Identify the altered chromosome 22 as the Philadelphia chromosome and explain the fusion's persistent kinase activity. Correlate with morphology, lineage studies, and clinical findings before classifying the disease. The NCI definition also identifies chromosome 22 and these disease associations: https://www.cancer.gov/publications/dictionaries/cancer-terms/def/philadelphia-chromosome.

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A homolog differs mainly in a heterochromatic region while its expected euchromatic band pattern is preserved. Evaluate whether the finding fits a recognized variant before diagnosing a deletion, duplication, or clinically significant structural rearrangement.

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For 12 trisomy-21 and 8 normal constitutional metaphases, mos 47,XX,+21[12]/46,XX[8] identifies mosaicism, separates populations with /, and gives each count. For a separate nonmosaic trisomy-21 case, matching interphase documentation nuc ish(D21S259)×3[100] means interphase hybridization, the D21S259 probe target, three signals, and 100 scored nuclei. ISCN 2024 places × outside parentheses for this single-probe pattern; locus gain alone does not establish chromosome structure.

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Cultured chromosome analysis detects a minor abnormal population that is not identified by a targeted assay on uncultured cells. Compare target relevance, detection capability, population selection, and specimen identity before deciding whether the findings are genuinely contradictory.

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A newly identified reagent problem may affect recent harvests. Use lot and preparation records to identify exposed cultures and associated analyses, then evaluate their quality rather than recalling every result produced during an arbitrary calendar interval.

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An independent incubator monitor disagrees with the displayed temperature. Investigate the discrepancy, protect ongoing cultures, and assess the period of possible exposure instead of accepting the display because it shows the usual programmed setting.

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A specimen-processing step can generate droplets near the operator's face. Assess task-appropriate containment and protective equipment, then ensure contaminated consumables and sharps enter their designated waste streams rather than relying only on gloves to control exposure.

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A worker needs to respond to a fixative spill and is unsure about exposure hazards. Use the accessible safety data sheet and established emergency procedure to select the appropriate response rather than improvising from the reagent's familiar laboratory use.

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Culture failure rises after a supply change. Compare affected specimens, reagent lots, and equipment records, implement a supported correction, and monitor subsequent performance to determine whether the change actually reduced failures without introducing a new problem.

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A trainee can recite FISH processing steps but repeatedly accepts nuclei that fail scoring criteria. Provide targeted supervised practice and assess real slide selection and interpretation before authorizing independent analysis of that task in the laboratory.

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A laboratory employee recognizes a public figure's name in the worklist but has no assigned role in the case. Do not open the record out of curiosity; access should follow the employee's authorized duties and institutional privacy policies.