# SF3B1 mutation

Source: https://onco.cc/terms/sf3b1-mutation/  
OnCo record `sf3b1-mutation` (Term). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

SF3B1 is a splicing gene whose mutation makes the marrow produce red cells with iron-stuffed mitochondria (ring sideroblasts); in myelodysplastic syndrome it defines a low-risk subtype with anaemia that responds to luspatercept, whereas in CLL and uveal melanoma the same mutation has different, mostly adverse or delayed-relapse, meaning.

## Summary

What is measured: a hotspot mutation in the splicing factor SF3B1 (K700E most often, also K666, R625, H662, E622) and its marrow correlate, ring sideroblasts. How: a myeloid sequencing panel on marrow or blood, and an iron (Perls) stain counting ring sideroblasts, which WHO 2016 required at 15 percent (or 5 percent with the mutation) and WHO 2022 no longer requires, defining MDS with low blasts and SF3B1 mutation directly. Frequencies: 25 to 30 percent of MDS (some 80 percent of those with ring sideroblasts), RARS-T with JAK2, about 10 percent of CLL (adverse, often with ATM loss), about 20 percent of uveal melanoma (R625, associated with late metastases), mucosal melanoma, and rarely breast and pancreatic cancers. What a result changes: in MDS the IPSS-M treats an isolated SF3B1 mutation as favourable but not when it comes with del(5q) or other adverse mutations; the anaemia is managed with erythropoiesis-stimulating agents and then luspatercept (transfusion independence in 38 percent against 13 percent on placebo in MEDALIST, and superiority over epoetin first line in COMMANDS) or imetelstat, with iron chelation for overload; splicing modulators such as H3B-8800 failed in the clinic; in CLL it feeds prognostic models without a matched drug; in uveal melanoma it flags a class 1B tumour that needs longer surveillance. Where it matters: lower-risk MDS, CLL, uveal and mucosal melanoma, secondary AML and CMML.

## Fields

- Kind: Term
- Last checked: 2026-09-17
- Also known as: SF3B1; SF3B1-mutated; SF3B1-mutant; SF3B1 K700E; splicing factor 3b subunit 1; MDS-SF3B1; MDS with ring sideroblasts; MDS-RS; ring sideroblasts; refractory anaemia with ring sideroblasts; RARS; RARS-T; MDS/MPN with ring sideroblasts and thrombocytosis

## Sources

- Wikipedia: https://en.wikipedia.org/wiki/SF3B1
- Wikipedia: https://en.wikipedia.org/wiki/SF3B1

## Connected records

- terms: [AML with myelodysplasia-related gene mutations (AML-MR)](https://onco.cc/terms/aml-myelodysplasia-related/), [CLL-IPI (chronic lymphocytic leukaemia prognostic index)](https://onco.cc/terms/cll-ipi/), [IPSS-R and IPSS-M (myelodysplastic syndrome risk scores)](https://onco.cc/terms/ipss-m-ipss-r/), [Next-generation sequencing (NGS)](https://onco.cc/terms/ngs/), [Uveal melanoma prognostic markers (GNAQ/GNA11, monosomy 3, gene-expression class)](https://onco.cc/terms/uveal-melanoma-prognostic-markers/)
- drugs: [Imetelstat](https://onco.cc/drugs/imetelstat/), [Luspatercept](https://onco.cc/drugs/luspatercept/)
- cancers: [Acral melanoma](https://onco.cc/cancers/acral-melanoma/), [Chronic lymphocytic leukaemia](https://onco.cc/cancers/cll/), [Chronic myelomonocytic leukaemia and MDS/MPN overlap neoplasms](https://onco.cc/cancers/cmml/), [Lower-risk myelodysplastic syndromes](https://onco.cc/cancers/mds-lower-risk/), [Mucosal melanoma](https://onco.cc/cancers/mucosal-melanoma/), [Secondary and therapy-related acute myeloid leukaemia](https://onco.cc/cancers/aml-secondary/), [Uveal melanoma](https://onco.cc/cancers/uveal-melanoma/)

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