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Uterine adenosarcoma — Overview

TL;DR — Uterine adenosarcoma is a rare biphasic Müllerian tumour: benign (or at most atypical) epithelium plus a malignant stromal component, originally described in a 10-case series in 1974 (Clement 1974, PMID 4371193). Recurrence estimates are case-mix dependent: 23/100 in the classic series and, within stage I at one referral centre, 77% with sarcomatous overgrowth versus 22% without (Clement 1990, PMID 2156771; Carroll 2014, PMID 25449308). Sarcomatous overgrowth is the one histological finding with consistent independent support: in a 74-patient single-institution cohort it separated median PFS of 29.4 from 105.9 months (HR 2.58, 95% CI 1.37–4.84) and OS of 55.4 from 112.4 months (HR 2.45, 95% CI 1.26–4.76) (Carroll 2014, PMID 25449308). Outside single centres the evidence is registry-based and lacks central pathology review: 797 SEER patients supported a survival model with c-index 0.774 (Qu 2020, PMID 33680946); a Japanese literature-assembled series of 110 cases found disease-specific death in 34% (Tate 2018, PMID 29441675). Preoperative diagnosis is the safety problem underneath all of this: occult uterine sarcoma was found in 1 of 278 hysterectomies performed for presumed leiomyomas (Raine-Bennett 2016, PMID 26646120).

What it is

Adenosarcoma is a mixed epithelial–mesenchymal neoplasm in which the epithelium is benign (or at most atypical) and the stroma is sarcomatous (Clement 1974, PMID 4371193; Pinto 2016, PMID 26927725). The original 1974 description distinguished it from carcinosarcoma (then “malignant mixed Müllerian tumour”) by the absence of a malignant epithelial component (Clement 1974, PMID 4371193). WHO 2014 places it among mixed epithelial and mesenchymal tumours of the uterus, alongside carcinosarcoma, adenofibroma, adenomyoma and atypical polypoid adenomyoma (McCluggage 2016, PMID 26715175).

The typical gross picture is a polypoid endometrial mass, often filling the cavity and sometimes protruding through the cervix; spongy cut surfaces with cystic spaces are common (Clement 1990, PMID 2156771). Histology shows leaf-like (phyllodiform) architecture, periglandular stromal cuffing, and a stromal mitotic rate that in the 100-case Clement series ranged from 1 to 40 mitoses per 10 high-power fields (mean 9) (Clement 1990, PMID 2156771). Diagnostic criteria versus adenofibroma have never been fully settled; Gallardo and Prat argued that some tumours labelled adenofibroma on mitotic-count grounds are well-differentiated adenosarcomas (Gallardo 2009, PMID 18941402). Detail lives in pathology and diagnosis.

Uterine adenosarcomas account for approximately 5% of uterine sarcomas in reviews that compile the published series (Nathenson 2016, PMID 27718181; Friedlander 2014, PMID 25341585). In the National Cancer Data Base they represented 0.43% of uterine, 0.16% of cervical and 0.04% of ovarian cancers (Seagle 2016, PMID 27771166). Most patients present with stage I disease (Arend 2010, PMID 20688363). See epidemiology and burden.

Why “low-grade” misleads

A 2018 narrative review states that “at least 50%” develop recurrence (Nathenson 2018, PMID 30169984), but that is a synthesis of case reports and retrospective series, not a cohort estimate. Primary-series estimates vary with stage and sarcomatous overgrowth: Clement reported 23/100 overall, while Carroll reported stage I recurrence of 77% with overgrowth versus 22% without (Clement 1990, PMID 2156771; Carroll 2014, PMID 25449308). Without overgrowth, stage I disease can have 5-year overall survival approaching 80% (Karabajakian 2023, PMID 37202293; Ulrich 2018, PMID 30326467). With overgrowth, the French guideline quotes 5-year OS of 50–60% and the 2016 review compiles recurrence of 77% versus 23% (Karabajakian 2023, PMID 37202293; Nathenson 2016, PMID 27718181). In Tanner’s 31-patient Memorial Sloan Kettering series, 2-year PFS and OS were both 20% with sarcomatous overgrowth versus 100% without (Tanner 2013, PMID 23283300). Only five up-front-treated patients had overgrowth, so these percentages are unstable; the direction matches Carroll’s larger retrospective analysis (Carroll 2014, PMID 25449308).

The practical consequence is that a polypoid endometrial mass labelled “adenosarcoma, low-grade” is not a licence to treat it as a benign polyp. Five of Clement’s 100 patients had presented on multiple occasions with “recurrent polyps” that were adenosarcomas in retrospect (Clement 1990, PMID 2156771). Polyps that overlap morphologically with adenosarcoma but fall short of the diagnosis have a benign course even with conservative management (Howitt 2015, PMID 25118811; Chapel 2022, PMID 34675347) — the diagnostic line is the clinical problem, not a semantic one. See sarcomatous overgrowth and red flags and safety concerns.

What actually predicts outcome

No adenosarcoma-only randomised trial or adenosarcoma-specific randomised outcome has been reported. A mixed-histology phase 3 adjuvant chemoradiotherapy study registered adenosarcoma as eligible in 2005, but its ClinicalTrials.gov status is unknown, its enrolment remains estimated, and no results are posted (NCT00162721; registry rechecked 2026-09-01). Every prognostic claim below is from retrospective series, registry extracts, or reviews of those series.

Factor What the largest analyses show Grade of evidence
Sarcomatous overgrowth Independent predictor of PFS and OS in Carroll n=74 (PFS HR 2.58, 1.37–4.84; OS HR 2.45, 1.26–4.76); “the only established histological variable associated with higher stage and shorter survival” in Howitt’s genomic series Single-institution cohort with multivariable analysis (Carroll 2014, PMID 25449308; Howitt 2015, PMID 25231023)
Lymphovascular invasion Median OS 1.0 vs 8.9 years in Nathenson n=165; retained on Cox analysis with SO, myometrial invasion, age, resection status and FIGO stage Single-institution series, sarcoma-pathologist review (Nathenson 2018, PMID 30044322)
Myometrial invasion The only feature associated with recurrence in Clement’s 100 cases; deep invasion in Zaloudek’s 25 adenosarcomas correlated with aggressive behaviour Classic clinicopathologic series (Clement 1990, PMID 2156771; Zaloudek 1981, PMID 6263458)
Lymph node metastasis Incidence 2.9% in SEER (n=994); independently associated with cause-specific survival (aHR 2.34), comparable in magnitude to ESS and LMS Registry, no central pathology review (Machida 2017, PMID 28109626)
Age Named as a prognostic factor in the Nathenson review; independently associated with OS in NCDB Review + registry (Nathenson 2018, PMID 30169984; Seagle 2016, PMID 27771166)
FIGO stage Stage I 5-year survival 79% (95% CI 75–84%) vs stage III 48% (29–65%) in SEER adenosarcoma Registry (Arend 2010, PMID 20688363)

The SEER deep-learning model of 797 patients reached a c-index of 0.774, better than a Cox model at 0.726, but registries do not capture sarcomatous overgrowth, LVSI, or central pathology review (Qu 2020, PMID 33680946). How much that omission distorts estimates is an open question — see staging and prognostic factors.

What is done, and how little is known about doing it

Standard treatment is hysterectomy, usually with bilateral salpingo-oophorectomy (Nathenson 2016, PMID 27718181; Friedlander 2014, PMID 25341585). Lymphadenectomy is not supported as routine: nodal metastasis is uncommon (2.9–3.1% in SEER/NCDB) and no trial has shown a survival benefit from the dissection (Machida 2017, PMID 28109626; Seagle 2016, PMID 27771166). Ovarian preservation in premenopausal stage I disease is practised; a 31-patient institutional series found no recurrences among 6 patients whose ovaries were kept, and a SEER analysis of stage I uterine sarcoma (162 adenosarcomas nested in 1,482 sarcomas) found ovarian preservation not associated with worse OS or CSS — but the adenosarcoma subset was too small for a histology-specific conclusion (Li 2022, PMID 35005157; Nasioudis 2017, PMID 28541635). Fertility-sparing management exists as case-level evidence, including a 20-year follow-up of one conservatively managed patient who later had live births and a completion hysterectomy without recurrence (L’Heveder 2019, PMID 31584132). That is a case report, not a strategy. See surgical management.

Adjuvant chemotherapy and radiotherapy have no defined role. Carroll’s stage I patients with sarcomatous overgrowth had numerically longer PFS and OS with adjuvant therapy (46.7 vs 29.4 months PFS; 97.3 vs 55.4 months OS) that did not reach statistical significance (p=0.28 and 0.18) (Carroll 2014, PMID 25449308). Nathenson found no OS or local-recurrence-free survival difference for adjuvant radiation (Nathenson 2018, PMID 30044322). ESGO/EURACAN/GCIG 2024 and the 2023 French GSF/TMRG guideline both state that adjuvant therapy is not established for stage I disease without overgrowth (Ray-Coquard 2024, PMID 39322612; Karabajakian 2023, PMID 37202293). For recurrent or metastatic disease, a 78-patient MD Anderson series reported RECIST response of 31.2% for doxorubicin-based regimens and 14.3% for gemcitabine/docetaxel, with median PFS 15.4 months for doxorubicin/ifosfamide versus 5.0 months for gemcitabine/docetaxel — a retrospective, non-randomised comparison (Nathenson 2017, PMID 29445312). See adjuvant and systemic therapy.

Map of this wiki

Pathology, the adenofibroma/carcinosarcoma differential, and the polyps that mimic adenosarcoma are in pathology and diagnosis. Sarcomatous overgrowth has its own page because it is the single most decision-relevant fact about the disease. Copy-number and mutational findings — MDM2/CDK4, TERT, DICER1, BAP1, TP53 in high-grade tumours — and what is not yet a diagnostic test are in molecular and genomic features. Incidence, age, and why case-mix differs between series are in epidemiology and burden. Bleeding, polypoid mass, MRI features and the fibroid/polyp differential are in clinical presentation and imaging. FIGO staging unique to adenosarcoma (IA = no myometrial invasion) and the prognostic-factor table are in staging and prognostic factors. Surgery, adjuvant/systemic therapy, recurrence patterns and surveillance, society guidance, the (almost empty) trial landscape, preoperative misdiagnosis and morcellation, and the lived-experience layer follow in that order.

Open questions

  • Is anything other than sarcomatous overgrowth independently prognostic once series are restricted to multivariable models with sarcoma-pathologist review? LVSI is the leading candidate (Nathenson 2018, PMID 30044322), but the analyses remain single-institution.
  • Does adjuvant therapy change outcome in any subgroup? Carroll’s non-significant numerical benefit in stage I with overgrowth is the strongest available signal and is still compatible with no effect (Carroll 2014, PMID 25449308).
  • Can preoperative diagnosis be made reliably enough to avoid morcellation? MRI features have been catalogued (Morikawa 2025, PMID 39729099) but not prospectively tested against the fibroid/polyp differential.

References

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