Number of Karyograms
The number of karyograms (images) prepared for the final report is not arbitrary; it is dictated by the complexity of the case and the regulatory requirement to document the diagnosis fully. While the laboratory scientist analyzes many cells through the eyepieces, the “Karyogram Record” serves as the visual proof of that analysis
Routine Normal Case (Constitutional)
- Diagnosis: Normal Male (46,XY) or Normal Female (46,XX)
- Requirement: Typically 2 Karyograms
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Rationale
- Provides redundancy (if one image has a hidden overlap, the second clarifies it)
- Demonstrates that the “normal” finding is consistent across multiple cells
- Often, labs prepare one karyogram from a 400-band cell and one from a 550-band cell (if available) to show resolution
Routine Normal Case (Oncology)
- Diagnosis: Normal (46,XX) in a leukemia workup
- Requirement: Typically 2 Karyograms
- Note: Even though oncology requires counting/analyzing 20 cells, capturing 2 representative images is sufficient to document the “Normal” status
Clonal Abnormality (Single Clone)
- Diagnosis: Single abnormal clone (e.g., Trisomy 21 or t(8;21))
- Requirement: 2 Abnormal Karyograms
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Rationale
- Visual proof of Clonality. Showing two separate cells with the same defect visually satisfies the ISCN definition of a clone (2 cells for structural/gains)
- If the defect is subtle (e.g., a deletion), having two images allows the reviewer to compare the breakpoints and confirm consistency
Mosaicism (Two Cell Lines)
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Diagnosis: Mosaic (e.g.,
45,X[12]/46,XX[8]) -
Requirement: At least 1 of EACH cell line
- One Karyogram of the 45,X line
- One Karyogram of the 46,XX line
- Total: Minimum 2 images. (Some labs prefer 2 of the abnormal + 1 normal)
- Rationale: The report must visually prove the existence of both populations. Showing only the abnormal cells hides the fact that normal cells were also present
Clonal Evolution (Multiple Sub-Clones)
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Diagnosis: Complex evolution (e.g.,
46,XY,t(9;22)[10]/47,XY,t(9;22),+8[10]) -
Requirement: At least 1 of EACH clone
- One Karyogram of the Stemline (t(9;22) only)
- One Karyogram of the Sideline (t(9;22) +8)
- Total: Minimum 2 images
- Rationale: This documents the “Evolutionary Tree” of the cancer. The physician needs to see the progression
Composite Karyotype (CP)
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Diagnosis: Highly complex cancer with random losses (e.g.,
43~48,XX,del(5q),-7,+8,...[cp20]) - Requirement: 2 Representative Abnormal Karyograms
- Selection: The laboratory scientist selects two cells that show the most common or most critical abnormalities (e.g., cells that definitely show the del(5q) and -7), even if the random losses vary between the two images
- Note: It is impossible to capture a “perfect” representative cell in composite cases because every cell is slightly different. The goal is to capture the “average” complexity