OPEN ACCESS

CASE REPORT

Synchronous Retrorectal Tumor and Low Rectal Cancer:

Surgical Management and Literature Review

Valentina Molina, MD¹; Alfonso Nuñez, MD²; María I. Ortiz S., MD²; Oscar E. Molina, MD³

¹General Surgeon

²General Practitioner

³Colorectal Surgeon

Service of General Surgery, Coloproctology Unit, Viña del Mar–Quillota Health Service, Biprovincial Quillota-Petorca Hospital, Quillota,

Valparaíso, Chile

ABSTRACT

To cite:

The management of early rectal cancer has progressively evolved toward organ-preserving strategies in selected patients.

However, outcomes following local excision after neoadjuvant therapy remain heterogeneous, particularly in patients with residual

ypT2 disease. Retrorectal tumors are rare lesions, most of which are benign, although surgical excision remains the standard

treatment. The synchronous occurrence of both conditions is exceptionally uncommon.

A 41-year-old woman was diagnosed with cT2N0M0 low rectal adenocarcinoma. Total neoadjuvant therapy was initially

administered with an organ-preservation intent. Restaging demonstrated a partial response (yT1N0), and transanal local excision

was subsequently performed. Final pathology revealed ypT2 disease with an extremely close deep margin. Given these high-risk

features, laparoscopic abdominoperineal resection with en bloc excision of a synchronous retrorectal lesion was undertaken.

Histopathological examination confirmed an epidermoid cyst. The postoperative course was uneventful, and the patient remains

free of local or distant recurrence at 6 months of follow-up.

Molina V, Nuñez A, Ortiz SMI, Molina OE.

Synchronous Retrorectal Tumor and Low

Rectal Cancer: Surgical Management and

Literature Review. Rev Argent Coloproctol.

2026; 37(2):15-20. doi:10.46768/7ym87846

Additional supplemental material, when

applicable, is published online only. To view,

please visit the journal online:

https://doi.org/10.46768/7ym87846

This case highlights the challenges associated with organ-preserving strategies in early rectal cancer and the management of

synchronous retrorectal lesions. Although local excision following neoadjuvant therapy may be appropriate in highly selected

patients, ypT2 tumors continue to carry a substantial risk of recurrence. In selected asymptomatic patients with benign-appearing

retrorectal cystic lesions, surveillance may be considered; however, surgical excision remains the standard approach.

Received: August 18, 2025

Accepted: April 21, 2026

Keywords: early rectal cancer; local excision; total mesorectal excision; neoadjuvant chemoradiotherapy; organ preservation;

retrorectal tumor; epidermoid cyst

high local recurrence rates in T2N0 tumors. Several

studies have suggested that neoadjuvant therapy

followed by LE may reduce this risk in carefully

selected patients.^1,2

Retrorectal (presacral) tumors are rare lesions

derived from embryologic remnants. Although most

are benign, malignant subtypes have been described

(Table 1).⁴ Their incidence is estimated at

INTRODUCTION

Total mesorectal excision (TME) remains the

standard treatment for mid and low rectal cancer,

particularly for T2–T4 tumors.^1,2Neoadjuvant

therapy plays a pivotal role in locally advanced

disease by reducing local recurrence rates and

improving

disease-free

survival.³

Despite

approximately

per 40,000–60,000 hospital

substantial advances in rectal cancer management,

many patients experience significant long-term

impairment in quality of life following TME,

prompting the development of organ-preserving

strategies aimed at maintaining anorectal function

without compromising oncologic outcomes.

Local excision (LE) is an accepted treatment for

selected early-stage rectal neoplasms (T1N0) with

favorable histologic features, size, and location.

However, LE alone is associated with unacceptably

admissions annually in tertiary referral centers.⁵

These lesions are frequently asymptomatic and are

traditionally managed by surgical resection.

We report the case of a young woman with low

rectal adenocarcinoma and a synchronous retrorectal

tumor, illustrating the complexity of decision-

making when two conditions with potentially

conflicting management strategies coexist.

2026 The authors. Published by Revista

Argentina de Coloproctología. This article is

distributed under the Creative Commons

Attribution–NonCommercial–NoDerivatives

4.0 International License (CC BY-NC-ND

4.0)

Table 1. Classification of the most common retrorectal tumors

Tumor category

Congenital

Benign

Malignant

Epidermoid/dermoid cyst

Enteric cyst

Tailgut cyst (cystic hamartoma)

Malignant transformation of a cystic

hamartoma* Teratocarcinoma (solid)

https://creativecommons.org/licenses/by

nc-nd/4.0/

Teratoma (solid)

Schwannoma

Neurofibroma

Aneurysmal bone cyst

Osteoma

Simple bone cyst

Schwannoma

Neurofibrosarcoma

Chordoma

Chondrosarcoma

Neurogenic

Osseous

Gastrointestinal stromal tumor (GIST)

Hemangiopericytoma

Desmoid tumor angiomyxoma

Metastatic carcinoma

Angiosarcoma

Carcinosarcoma

Miscellaneous

Fibrosarcoma

Correspondence to

Oscar Eduardo Molina Saez

omolinasaez@gmail.com

* Low risk of malignant transformation.

located 2 cm from the anal verge without fixation to

adjacent structures.

CASE PRESENTATION

Colonoscopy confirmed the presence of the lesion,

and biopsy demonstrated moderately differentiated

rectal adenocarcinoma with proficient mismatch

repair status (pMMR).

A 41-year-old woman presented with a 3-month

history of hematochezia, tenesmus, and a 5-kg

weight loss. Digital rectal examination revealed an

irregular, ulcerated, friable, partially mobile mass

REV ARGENT COLOPROCTOL | 2026 | VOL 37, No. 2

CASE REPORT

Pelvic magnetic resonance imaging (MRI) showed

circumferential thickening of the distal rectal wall located 1.1 cm

above the dentate line, measuring 5.2 cm longitudinally and 4.4

cm transversely, with invasion limited to the muscularis propria.

There was no evidence of sphincter complex involvement,

mesorectal lymphadenopathy, threatened circumferential

resection margin, or extramural vascular invasion. Clinical

staging was cT2N0Mx (Fig. 1).

a strong preference for organ preservation and surveillance of the

asymptomatic retrorectal lesion.

Total neoadjuvant therapy (TNT) was administered using a

consolidation approach consisting of short-course radiotherapy

followed by six cycles of FOLFOX chemotherapy.

Eight weeks after completion of TNT, digital rectal examination

and rigid proctoscopy demonstrated a residual flat elevated lesion

measuring 2.9

2.2 cm. Restaging MRI showed tumor

Computed tomography (CT) of the chest, abdomen, and pelvis

revealed no distant metastases or suspicious lymph nodes.

Both MRI and CT incidentally identified a 5.2 × 4.5 cm

retrorectal lesion characterized by smooth, well-defined margins

and mixed cystic-solid contents suggestive of a developmental

cyst or hamartoma. Following multidisciplinary discussion,

treatment options were reviewed with the patient, who expressed

involvement confined to the submucosa with contact but no

invasion of the muscularis propria, no sphincter involvement, and

no nodal disease, corresponding to yT1N0Mx with MRI tumor

regression grade 3 (Fig. 2).

Figure 1. Colonoscopy. A. Endoscopic view of rectal adenocarcinoma before neoadjuvant chemoradiotherapy. B. Endoscopic view demonstrating tumor

regression after neoadjuvant therapy.

Figure 2. MRI in the sagittal plane with T2-weighted sequences. A. Pre-neoadjuvant image. B. Post-neoadjuvant image. Images demonstrate irregular hypointense

thickening of the distal rectal wall, consistent with low rectal adenocarcinoma (A), and a well-defined, homogeneously hyperintense retrorectal cystic lesion,

consistent with a retrorectal cyst (B).

Given the possibility of achieving complete excision of a residual

T1 lesion while preserving sphincter function, conventional

transanal local excision was performed. Pathological examination

revealed a 2.5 × 2.8 cm residual adenocarcinoma staged as

ypT2NxMx. There was no lymphovascular invasion, perineural

invasion, or high-grade tumor budding. The lateral margin was

negative (10 mm), whereas the deep margin measured only 0.2

mm.

completion laparoscopic abdominoperineal resection was

recommended and performed together with en bloc excision of

the retrorectal lesion (Fig. 3).

Final pathology demonstrated moderately differentiated tubular

adenocarcinoma with focal mucin production in the local excision

scar. All mesorectal lymph nodes were negative (0/14), and

resection margins were clear. The retrorectal lesion was

confirmed as an epidermoid cyst.

Because of the high risk of local recurrence associated with

residual ypT2 disease, residual tumor size greater than 2 cm after

neoadjuvant therapy, and an extremely close deep margin,

At 6 months of follow-up, the patient remains free of local or

distant recurrence (Fig. 4).

SYNCHRONOUS RETRORECTAL TUMOR AND LOW RECTAL CANCER

Molina V, et al.

REV ARGENT COLOPROCTOL | 2026 | VOL 37, No. 2

CASE REPORT

Figure 3. Local excision of rectal adenocarcinoma. A. Posterior rectal wall defect following local excision. B. Resected specimen

4,674 patients reported local recurrence rates of 28.9%, 4.0%, and

14.7% for observation, completion TME, and adjuvant

radiotherapy/chemoradiotherapy, respectively, following LE of

pT2 tumors.¹³

DISCUSSION

Retrorectal tumors are rare lesions whose true incidence is

difficult to determine because most remain asymptomatic and are

detected incidentally during imaging studies. No established

association exists between retrorectal lesions and rectal

adenocarcinoma, making their coexistence exceedingly

uncommon. To our knowledge, only four similar cases have been

reported worldwide, with no previous reports from Latin

America.^6,7

The therapeutic strategy in this patient was particularly

challenging. Radical surgery with TME remains the standard

treatment for low rectal cancer. However, given the tumor

location and inability to guarantee adequate distal margins,

ultralow anterior resection was not feasible. Although

intersphincteric resection could potentially have achieved

adequate oncologic margins through partial internal sphincter

excision, the authors' prior experience with this approach has

demonstrated suboptimal functional outcomes. Considering the

patient's young age and desire for organ preservation,

conservative strategy was initially pursued.

TNT has been associated with increased rates of complete clinical

response and should be considered in patients seeking rectal

preservation.⁸ In patients with an incomplete but favorable

response, LE after neoadjuvant therapy is supported by several

studies (Table 2).^1,3,8-13

The ACOSOG Z6041 trial reported a pathological complete

response rate of 44% and downstaging to ypT0–1 in 64% of

patients treated with neoadjuvant chemoradiotherapy followed by

LE. However, the absence of a comparison group receiving

standard TME limits interpretation, and the authors

recommended this approach only in selected patients or those

unsuitable for radical surgery.⁹

Similarly, the GRECCAR 2 randomized trial evaluated patients

with T2–T3 low rectal adenocarcinoma and residual tumors ≤2

cm following chemoradiotherapy. Patients were randomized to

LE or TME, with completion TME mandated for ypT2–3 disease

or positive margins. Local recurrence rates at 5 years were low

and comparable between groups (5% vs 7%), with no differences

in survival outcomes. Nevertheless, a substantial proportion of

patients undergoing LE required completion TME, thereby

diminishing the potential benefits of organ preservation.¹⁰

The TAU-TEM study further demonstrated that neoadjuvant

chemoradiotherapy followed by LE was noninferior to TME in

carefully selected patients with early rectal cancer, offering a less

invasive alternative with comparable oncologic outcomes.¹¹

In a systematic review, Hallam et al. concluded that LE after

neoadjuvant therapy should be considered curative only when a

pathological complete response is achieved, given the high

recurrence rates observed among incomplete responders,

particularly those with ypT2 disease (23.6%).¹² Likewise, a

systematic review and meta-analysis including 73 studies and

Figure 4. Abdominoperineal resection specimen showing en bloc excision

of a retrorectal cyst (A).

Collectively, current evidence suggests that organ-preserving

approaches combining neoadjuvant therapy and LE may provide

oncologic outcomes comparable to TME in carefully selected

patients with cT1–T2N0 tumors or excellent treatment

responses.^1,9-11However, limitations including small sample

sizes, selection bias, heterogeneous inclusion criteria, and the

frequent need for completion TME continue to restrict broader

adoption. The most favorable outcomes are observed in patients

with complete clinical response or ypT0–1 disease, whereas ypT2

tumors remain associated with substantially higher recurrence

rates.^8,12,13

SYNCHRONOUS RETRORECTAL TUMOR AND LOW RECTAL CANCER

Molina V, et al.

REV ARGENT COLOPROCTOL | 2026 | VOL 37, No. 2

CASE REPORT

An additional consideration is the phenomenon of residual tumor

fragmentation ("tumor scatter"), whereby microscopic foci of

viable tumor may persist within fibrotic tissue after neoadjuvant

treatment. Consequently, LE may remove the visible residual

lesion while leaving occult tumor deposits within the original

tumor bed, potentially explaining residual disease identified in

subsequent TME specimens.¹⁴

preoperative imaging in predicting malignancy. MRI was

considered essential for initial evaluation, whereas preoperative

biopsy provided limited diagnostic benefit because of its high

false-negative rate. The authors recommended surgical resection

for symptomatic, solid, or large lesions, while small, thin-walled

cystic lesions and asymptomatic recurrences of benign tumors

may be considered for surveillance.

Regarding nonoperative management of retrorectal tumors,

Hopper et al. evaluated 69 patients and demonstrated that MRI

was significantly more accurate than CT in differentiating benign

from malignant lesions (94% vs 64%; p = 0.03). Based on the

high specificity of MRI for benign cystic lesions, the authors

suggested that selected asymptomatic patients could be managed

with serial imaging surveillance.¹⁵

In the present case, had a complete clinical response or an R0

resection of

management of the low-risk retrorectal lesion might have

represented reasonable alternative. However, because

ypT1 lesion been achieved, nonoperative

completion of radical surgery was indicated for oncologic

reasons, simultaneous resection of the retrorectal lesion was

performed.

Subsequently, Carpelan-Holmström et al.¹⁶ analyzed 52 patients

and reported low sensitivity (25%) but high specificity (98%) for

Table 2. Oncologic outcomes of local excision after neoadjuvant therapy in rectal cancer

Study design

Population / Stage of rectal

adenocarcinoma

Assessment

Outcomes

Author / Year

Park et al.¹

2024

Retrospective

comparative

119 patients, cT2N0, within 8

cm of the anal verge

nCRT + LE vs TME

3-year LRFS:

87.9% vs 96.2%; p = 0.129

3-year DFS: 79.6% vs 84.9%; p = 0.429

Peltrini et al.⁸

2022

Systematic review

(9 studies)

cT2N0

nCRT + LE

5-year DFS: 91.3%

5-year OS: 72.6%

LR: 4%

Garcia Aguilar et al.⁹

ACOSOG Z6041

2015

79 patients

cT2N0, within 8 cm of the

anal verge

nCRT + LE

cCR: 44%

Multicenter non-

randomized

Downstaging (ypT0–1): 64%

3-year DFS: OR 88.2% (95% CI 81.3–95.8)

LR: 8%

Rullier, et al.¹⁰

GRECCAR 2

2017

186 patients, cT2–T3N0,

within 8 cm of the anal verge,

good responders to CRT

(residual tumor <2 cm)

nCRT + LE vs TME

cCR: 40%

LR: 5% (nCRT + LE) vs 7% (TME)

Multicenter

prospective

randomized

Serra, et al.¹¹

TAUTEM

2025

Multicenter

prospective non-

inferiority

173 patients, cT2–

T3a/bN0M0, within 10 cm of

the anal verge, tumor ≤4 cm

LR: 7.4% vs 6.2%

DR: 12.3% vs 17.3%

3-year DFS: 82.7% vs 85.2%

randomized trial

Systematic review

(20 studies)

Hallam et al.¹²

2016

1.068 patients

nCRT + LE

Recurrence in ypT2: 23.6%

Combined DFS: 68%

Van Oostendorp et

al.¹³

2020

4.674 patients

pT1–T2

LE without nCRT vs

nCRT + LE vs TME

LR: 28.9% (LE without nCRT) vs 14.7%

(nCRT + LE) vs 4% (TME)

Meta-analysis

(73 studies)

Oliva et al.,³

2016

Prospective

53 patients, rectal

adenocarcinoma within 7 cm

of the anal verge

nCRT + LE with

follow-up vs. salvage

TME

ypT2: 68% (adverse features:

LVI/PNI/positive margins)

LR: 22%

CRM+: 87% (TME)

nCRT = neoadjuvant chemoradiotherapy. LE = local excision. TME = total mesorectal excision. LRFS = local recurrence–free survival. DFS = disease-free survival.

OS = overall survival. LR = local recurrence. cCR = clinical complete response. 95% CI = 95% confidence interval. DR: distant recurrence. LVI = lymphovascular

invasion. PNI = perineural invasion. CRM = circumferential resection margin.

This case underscores the importance of individualized decision-

making in early rectal cancer, prioritizing oncologic safety over

organ preservation when adverse pathological features are

present and evidence remains limited.

CONCLUSIONS

The coexistence of retrorectal tumors and low rectal

adenocarcinoma is exceptionally rare. Although local excision

following neoadjuvant therapy has been proposed as an organ-

preserving strategy for selected T2N0 rectal cancers, recurrence

rates remain substantial, particularly in patients with residual

tumors larger than 2 cm or ypT2 disease. Moreover, salvage

surgery after local recurrence may be associated with higher rates

of incomplete resection.

For benign-appearing retrorectal lesions, nonoperative

management may be considered in carefully selected

asymptomatic patients, despite surgical excision remaining the

conventional standard of care.

Author Contributions

VM: Conceptualization, Research, Writing – original draft. AN: Research, Data

curation, Writing – revision and editing. MO: Research, Writing – revision and

editing. OM: Project management, Research, Supervision, Writing – revision

and editing.

Conflict of interest statement: None.

Funding: None.

Data availability statement: The data are publicly available.

ORCIDS

Valentina Molina: 0009-0002-1889-8712

Alfonso Nuñez: 0009-0002-9610-405x

María Ortiz: 0009-0002-3923-4026

Oscar E. Molina Sáez: 0000-0002-8252-7548

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2022;37(5):1426–34.

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