# Sinonasal undifferentiated carcinoma (SNUC) and SWI/SNF-deficient sinonasal carcinoma

Source: https://onco.cc/cancers/sinonasal-undifferentiated-carcinoma/  
OnCo record `sinonasal-undifferentiated-carcinoma` (Cancer). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

Sinonasal undifferentiated carcinoma is a rare, fast-growing cancer of the nasal cavity and sinuses made of primitive cells with no clear line of differentiation, most carrying an IDH2 mutation. It presents as a large mass pressing on the eye or brain and is treated with chemotherapy first, then surgery or chemoradiotherapy depending on response; SMARCB1- or SMARCA4-deficient tumours are separate.

## Summary

Sinonasal undifferentiated carcinoma was defined in 1986 as a high-grade carcinoma of the sinonasal tract without squamous or glandular differentiation, negative for EBV and for the neuroendocrine and NUT markers that define its mimics. Genomic studies from 2017 found IDH2 R172 mutations in most cases, giving the tumour a molecular identity and a possible drug target; the 2022 WHO classification also carved out SMARCB1 (INI1)-deficient and SMARCA4-deficient sinonasal carcinomas, which look similar but are driven by loss of SWI/SNF chromatin remodelling proteins, and NUT carcinoma, which has its own page. All present late with a bulky mass causing nasal obstruction, proptosis, diplopia or headache, invading the orbit, skull base and dura, and about a fifth have neck node metastases at diagnosis.

Historically, surgery followed by radiotherapy cured few patients because of the extent of disease, and the MD Anderson group changed the paradigm by giving chemotherapy first. In their series of 95 patients (Journal of Clinical Oncology 2019), those whose tumour responded to induction platinum-etoposide did better with definitive chemoradiotherapy than with surgery, while those who did not respond did better with surgery followed by radiotherapy or chemoradiotherapy, so the response to induction now decides the local treatment. Intensity-modulated or proton radiotherapy is used to spare the optic pathways and brain, and elective neck treatment is standard because nodal relapse is common. Metastatic disease is treated with platinum-etoposide as for neuroendocrine carcinoma, and PD-1 antibodies have produced responses in case series of SMARCB1-deficient and other sinonasal carcinomas. The IDH2 inhibitor enasidenib, approved for IDH2-mutant leukaemia, is being tested in IDH2-mutant sinonasal carcinoma, and EZH2 inhibitors, active in other SMARCB1-deficient tumours, are being explored for the SWI/SNF-deficient group. Five-year survival remains low overall, and referral to a skull base centre with molecular pathology is recommended for every patient.

## Fields

- Kind: Cancer
- Last checked: 2026-09-18
- Also known as: SNUC; IDH2-mutant sinonasal carcinoma; SMARCB1-deficient sinonasal carcinoma; SMARCA4-deficient sinonasal carcinoma; Undifferentiated carcinoma of the paranasal sinuses
- Tags: subtype-page; head-and-neck
- Group: head and neck
- Burden: A rare and aggressive sinonasal cancer of middle-aged adults, usually presenting as a large mass invading the orbit or skull base; historically most patients died within a few years, and induction chemotherapy has improved that.
- Subtypes: IDH2-mutant sinonasal undifferentiated carcinoma (the majority; enasidenib in trials); IDH2 wild-type sinonasal undifferentiated carcinoma; SMARCB1 (INI1)-deficient sinonasal carcinoma (SWI/SNF-deficient; separate WHO entity); SMARCA4-deficient sinonasal carcinoma (SWI/SNF-deficient; separate WHO entity); Induction-responsive sinonasal undifferentiated carcinoma (definitive chemoradiotherapy); Induction-refractory sinonasal undifferentiated carcinoma (surgery then radiotherapy)
- Biomarkers: IDH2 R172 mutation (diagnosis; enasidenib eligibility); SMARCB1 (INI1) and SMARCA4 immunohistochemistry (SWI/SNF-deficient carcinomas); NUT immunohistochemistry (exclude NUT carcinoma) and EBV (exclude nasopharyngeal-type carcinoma); Response to induction chemotherapy on imaging (decides surgery versus chemoradiotherapy); Neck node status; PD-L1 (investigational)

## Sections of this record

The page is a hub with ten sections in reading order; large sections have their own page. The same plan as JSON: https://onco.cc/api/v1/cancers/sinonasal-undifferentiated-carcinoma/sections.json

- Overview (on the hub): The TL;DR, the family this cancer belongs to, the organ, who gets it and what the state of the art is. https://onco.cc/cancers/sinonasal-undifferentiated-carcinoma/#overview [3 state-of-the-art points]
- Types and stages (on the hub): Anatomy, the subtypes and how they differ, how it is staged, and where advanced disease spreads. https://onco.cc/cancers/sinonasal-undifferentiated-carcinoma/#what-it-is [6 subtypes]
- Symptoms and diagnosis (on the hub): How this cancer shows itself, how the diagnosis is confirmed, and the biomarkers clinicians test for. https://onco.cc/cancers/sinonasal-undifferentiated-carcinoma/#finding-it [6 biomarkers]
- Treatment (on the hub): The standard of care by setting, the medicines, surgery and radiotherapy named in it, and the regimens behind them. https://onco.cc/cancers/sinonasal-undifferentiated-carcinoma/#treating-it [5 settings, 5 decisions with options]
- Trials and papers (on the hub): Trials recruiting now, the landmark trials, the trials held by this cancer's subtypes, the key papers and what they mean, the latest literature, and the milestones year by year. https://onco.cc/cancers/sinonasal-undifferentiated-carcinoma/#evidence [2 key papers, 5 milestones]
- Biology and targets (on the hub): The molecular landscape: the targets and how often each appears, the pathways, the mechanics stages and the preclinical models. https://onco.cc/cancers/sinonasal-undifferentiated-carcinoma/#science [3 targets]
- Countries and centres (own page): Cases by country, the UK and NHS pathway and other country lenses, the expert centres with trials on record, and the centres named on this cancer's subtypes. https://onco.cc/cancers/sinonasal-undifferentiated-carcinoma/where-you-are/
- Decisions and support (on the hub): The decisions you may face, the aids that walk through them, the warnings on record, the first sixty days and the questions to ask. https://onco.cc/cancers/sinonasal-undifferentiated-carcinoma/#living-with-it [17 questions, 6 red cards]
- Pipeline and open problems (own page): Everything in development, the medicines held by this cancer's subtypes, the open problems and what is being done about them, the roadmaps, and what changed on this record. https://onco.cc/cancers/sinonasal-undifferentiated-carcinoma/coming/ [6 medicines, 4 open problems]
- Data (own page): Every connected record, the notes, the JSON, Markdown and RDF twins, and where the record came from and when it was checked. https://onco.cc/cancers/sinonasal-undifferentiated-carcinoma/data/ [30 connected records]

## Standard of care

- Diagnosis: Biopsy with immunohistochemistry (cytokeratins, NUT, INI1, SMARCA4, neuroendocrine markers, EBER) and IDH2 testing; MRI and CT of the sinuses, skull base and neck; PET-CT. ([Histopathology & immunohistochemistry](https://onco.cc/technologies/histopathology-ihc/), [MRI](https://onco.cc/technologies/mri/), [CT (computed tomography)](https://onco.cc/technologies/ct/), [PET/CT](https://onco.cc/technologies/pet-ct/))
- Locally advanced disease, first step: Induction chemotherapy with cisplatin and etoposide (or docetaxel-platinum) for two to three cycles. ([Cisplatin](https://onco.cc/drugs/cisplatin/), [Etoposide](https://onco.cc/drugs/etoposide/), [Platinum + etoposide (EP / CE)](https://onco.cc/drugs/platinum-etoposide/), [Cytotoxic chemotherapy](https://onco.cc/technologies/cytotoxic-chemotherapy/))
- Responders to induction: Definitive chemoradiotherapy with concurrent cisplatin (intensity-modulated or proton), including elective neck irradiation. ([Cisplatin](https://onco.cc/drugs/cisplatin/), [IMRT / IGRT (modern external beam)](https://onco.cc/technologies/imrt-igrt/), [Proton therapy](https://onco.cc/technologies/proton-therapy/), [Chemoradiation (chemoradiotherapy, CRT)](https://onco.cc/terms/chemoradiation/))
- Non-responders to induction: Surgical resection where feasible followed by radiotherapy or chemoradiotherapy. ([Robotic & minimally invasive surgery](https://onco.cc/technologies/robotic-surgery/), [IMRT / IGRT (modern external beam)](https://onco.cc/technologies/imrt-igrt/), [Chemoradiation (chemoradiotherapy, CRT)](https://onco.cc/terms/chemoradiation/))
- Metastatic or recurrent disease: Platinum-etoposide; PD-1 antibodies (pembrolizumab, nivolumab) on case series evidence; enasidenib for IDH2-mutant tumours in trials; EZH2 inhibitors for SWI/SNF-deficient carcinoma in trials. ([Platinum + etoposide (EP / CE)](https://onco.cc/drugs/platinum-etoposide/), [Pembrolizumab](https://onco.cc/drugs/pembrolizumab/), [Nivolumab](https://onco.cc/drugs/nivolumab/), [Enasidenib](https://onco.cc/drugs/enasidenib/), [Immune checkpoint inhibitors](https://onco.cc/technologies/checkpoint-inhibitor/))

## State of the art

- Response to induction chemotherapy now decides between surgery and chemoradiotherapy.
- IDH2 mutations give the tumour an identity and a drug target.
- SWI/SNF-deficient carcinomas have been separated as distinct diseases with their own emerging therapies.

## Open problems

- No randomised trial exists and the induction-response strategy rests on one centre's series.
- Enasidenib's activity in IDH2-mutant sinonasal carcinoma is unproven.
- Most patients still die of the disease within a few years.
- Orbital and skull base surgery and radiotherapy carry heavy functional costs.

## Sources

- Wikipedia: https://en.wikipedia.org/wiki/Sinonasal_undifferentiated_carcinoma
- Induction chemotherapy in SNUC (JCO 2019): https://doi.org/10.1200/JCO.18.00353
- NCCN Head and Neck Cancers (ethmoid and maxillary sinus): https://www.nccn.org/guidelines/guidelines-detail?category=1&id=1437
- Wikipedia: https://en.wikipedia.org/wiki/Sinonasal_undifferentiated_carcinoma

## Connected records

- cancers: [Esthesioneuroblastoma (olfactory neuroblastoma)](https://onco.cc/cancers/esthesioneuroblastoma/), [Extrapulmonary neuroendocrine carcinoma](https://onco.cc/cancers/extrapulmonary-nec/), [Nasal cavity and paranasal sinus cancers (including esthesioneuroblastoma)](https://onco.cc/cancers/sinonasal/), [NUT carcinoma (midline carcinoma with NUTM1 rearrangement)](https://onco.cc/cancers/nut-carcinoma/)
- technologies: [CT (computed tomography)](https://onco.cc/technologies/ct/), [Cytotoxic chemotherapy](https://onco.cc/technologies/cytotoxic-chemotherapy/), [Histopathology & immunohistochemistry](https://onco.cc/technologies/histopathology-ihc/), [Immune checkpoint inhibitors](https://onco.cc/technologies/checkpoint-inhibitor/), [IMRT / IGRT (modern external beam)](https://onco.cc/technologies/imrt-igrt/), [MRI](https://onco.cc/technologies/mri/), [PET/CT](https://onco.cc/technologies/pet-ct/), [Proton therapy](https://onco.cc/technologies/proton-therapy/), [Robotic & minimally invasive surgery](https://onco.cc/technologies/robotic-surgery/)
- targets: [IDH1 / IDH2](https://onco.cc/targets/idh/), [PD-1](https://onco.cc/targets/pd1/)
- drugs: [Cisplatin](https://onco.cc/drugs/cisplatin/), [Enasidenib](https://onco.cc/drugs/enasidenib/), [Etoposide](https://onco.cc/drugs/etoposide/), [Nivolumab](https://onco.cc/drugs/nivolumab/), [Pembrolizumab](https://onco.cc/drugs/pembrolizumab/), [Platinum + etoposide (EP / CE)](https://onco.cc/drugs/platinum-etoposide/)
- terms: [Chemoradiation (chemoradiotherapy, CRT)](https://onco.cc/terms/chemoradiation/), [Head and neck subsites (oral cavity, oropharynx, larynx)](https://onco.cc/terms/head-neck-subsites/), [Rare cancers](https://onco.cc/terms/rare-cancers/)
- key papers: [Induction chemotherapy response as a guide to treatment optimisation in sinonasal undifferentiated carcinoma](https://onco.cc/key-papers/paper-amit-induction-chemotherapy-response-snuc-jco-2019/), [Recurrent IDH2 R172X mutations in sinonasal undifferentiated carcinoma](https://onco.cc/key-papers/paper-jo-idh2-r172-mutations-snuc-mod-pathol-2017/)

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JSON: https://onco.cc/api/v1/entities/sinonasal-undifferentiated-carcinoma.json