Which cytogenetic abnormality in chronic lymphocytic leukemia is associated with the most favorable prognosis and is detected by fluorescence in situ hybridization (FISH)?

Question

Accepted Answer

C. Deletion 13q (del 13q). ## Cytogenetics and Prognosis in CLL

**Key Point:** Deletion 13q is the most common and most favorable cytogenetic abnormality in CLL, associated with longer overall survival and delayed need for treatment.

### CLL Cytogenetic Prognostic Hierarchy

| Abnormality | Frequency | Median OS | Prognosis |
|-------------|-----------|-----------|----------|
| del 13q (sole) | 55% | >10 years | Favorable |
| Trisomy 12 | 15% | 5–8 years | Intermediate |
| Normal karyotype | 25% | 5–8 years | Intermediate |
| del 11q | 10% | 5–7 years | Unfavorable |
| del 17p | 5% | 2–3 years | Very unfavorable |

### Mechanism and Clinical Implications
- **del 13q:** Involves loss of RB1 and other tumor suppressors; paradoxically associated with better outcomes
- **del 17p:** Loss of TP53 (p53 tumor suppressor); highly aggressive, resistant to conventional therapy, requires novel agents (venetoclax, BTK inhibitors)
- **del 11q:** ATM gene loss; intermediate-to-poor prognosis

**High-Yield:** FISH panel for del 13q, del 11q, del 17p, and trisomy 12 is standard prognostic workup in newly diagnosed CLL and guides treatment decisions.

**Clinical Pearl:** Patients with del 13q as sole abnormality may not require immediate treatment ("watch and wait"), whereas del 17p mandates early intervention with targeted agents.

**Warning:** ~~Trisomy 12 is favorable~~ — it is actually intermediate prognosis. Do not confuse with del 13q.

Answer

A. Deletion 11q (del 11q)

Answer

B. Trisomy 12

Answer

D. Deletion 17p (del 17p)

Which cytogenetic abnormality in chronic lymphocytic leukemia is associated with the most favorable prognosis and is detected by fluorescence in situ hybridization (FISH)?

Explanation

Cytogenetics and Prognosis in CLL

CLL Cytogenetic Prognostic Hierarchy

Mechanism and Clinical Implications

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Abnormality	Frequency	Median OS	Prognosis
del 13q (sole)	55%	>10 years	Favorable
Trisomy 12	15%	5–8 years	Intermediate
Normal karyotype	25%	5–8 years	Intermediate
del 11q	10%	5–7 years	Unfavorable
del 17p	5%	2–3 years	Very unfavorable