Unusually rapid growth of a duodenal muco-submucosal elongated polyp: A case report

Abstract

BACKGROUND

Muco-submucosal elongated polyps (MSEPs) are rare benign gastrointestinal lesions, typically reported in the colon and seldom observed in the small intestine. These polyps are generally slow-growing and asymptomatic, making diagnosis and management challenging. Rapid enlargement of MSEPs in the duodenum is particularly rare and may raise suspicion for neoplastic potential.

CASE SUMMARY

We report the case of a 64-year-old female who presented with nausea and abdominal pain. Abdominal computed tomography revealed a soft tissue density in the descending duodenum. Upper endoscopy performed 15 months earlier had identified a 1.5-cm mucosal elevation in the second portion of the duodenum. On follow-up endoscopy, the lesion had enlarged significantly into a 10-cm elongated, pedunculated polyp. Endoscopic submucosal dissection was performed for complete en bloc resection. Histopathology confirmed the diagnosis of a MSEP, with no evidence of malignancy. Surveillance endoscopy performed one year after resection showed no recurrence.

CONCLUSION

Although MSEPs are typically benign, our case demonstrates that rapid growth may occur. This highlights the importance of continued endoscopic surveillance and early intervention, even in asymptomatic patients, to prevent potential complications and ensure timely diagnosis.

Key Words: Muco-submucosal elongated polyp; Duodenal lesion; Histopathology; Endoscopy; Case report

Core Tip: Muco-submucosal elongated polyps (MSEPs) are rare benign gastrointestinal lesions, typically found in the colon and infrequently in the small intestine. We report a case of a rapidly enlarging MSEP in the duodenum, which expanded from a 1.5-cm mucosal elevation to a 10-cm pedunculated lesion within 15 months. Complete en bloc resection was achieved by endoscopic submucosal dissection, and histology confirmed the diagnosis. This case highlights the potential for rapid growth of duodenal MSEPs and emphasizes the importance of regular endoscopic surveillance, even in patients without symptoms.

INTRODUCTION

Muco-submucosal elongated polyps (MSEPs) are rare, benign gastrointestinal lesions[1], most commonly found in the colon and rarely in the small intestine[2,3]. Endoscopically, these polyps appear as long, slender, worm-like appearance, pedunculated structures, and histologically consist of hyperplastic mucosa and submucosal connective tissue with dilated lymphovascular spaces[4]. Though typically asymptomatic and non-neoplastic, they may occasionally cause intussusception[5], diverticulitis[6], and non-polypoid neoplasia[7,8]. We report a rare case of a duodenal MSEP with unusually rapid growth over 15 months, highlighting the importance of endoscopic surveillance and timely intervention.

CASE PRESENTATION

Chief complaints

A 64-year-old female was admitted with complaints of nausea and upper abdominal pain lasting for 2 weeks.

History of present illness

The patient reported intermittent nausea and upper abdominal discomfort for several days prior to admission. She denied vomiting, melena, hematemesis, and significant weight loss. There was no history of recent changes in appetite or bowel habits.

History of past illness

The patient had a 1-year history of hypertension and a 3-year history of coronary artery atherosclerotic heart disease. She underwent percutaneous coronary intervention with coronary stent implantation 3 years earlier and had been on regular follow-up since then. Chronic medications included clopidogrel, atorvastatin calcium, and olmesartan medoxomil.

Personal and family history

No special personal history, and family history.

Physical examination

On admission, the patient was afebrile with stable vital signs. Abdominal examination revealed no tenderness, rebound pain, or palpable mass in the upper abdomen.

Laboratory examinations

Laboratory tests revealed normal results for routine blood, urine, and stool analyses, as well as liver and kidney function. Tumor markers, including carcinoembryonic antigen, alpha-fetoprotein, and carbohydrate antigen 19-9, were also within normal limits.

Imaging examinations

Abdominal computed tomography revealed a strip-like soft tissue density lesion in the descending portion of the duodenum, measuring approximately 10 cm in length. The lesion exhibited mild to moderate enhancement on contrast-enhanced imaging, suggesting a subepithelial origin (Figure 1). Fifteen months earlier, upper endoscopy had identified a mucosal elevation measuring approximately 1.5 cm in diameter in the second portion of the duodenum (Figure 2A). On repeat endoscopy, the lesion had significantly enlarged, appearing as a 10-cm slender, elongated, pedunculated mass with a smooth surface, arising from the duodenal mucosa (Figure 2B and C). Narrow band imaging did not reveal any adenomatous or suspicious features (Figure 2D). This indicated rapid growth over a relatively short period of 15 months, raising clinical concern despite the typically benign nature of such lesions.

Figure 1  Computed tomography revealed a strip-like soft tissue density lesion in the descending duodenum (arrows).

Figure 2 Endoscopic views of the polyps. A: Gastroduodenoscopy performed 15 months earlier showing a 1.5-cm mucosal elevation in the second portion of the duodenum; B and C: Gastroduodenoscopy revealed a 10-cm slender, elongated, pedunculated, “worm-like mass with a smooth surface in D2; D: Endoscopic view under narrow band imaging.

FINAL DIAGNOSIS

The resected specimen measured 90 mm × 17 mm and was submitted for histopathological examination. Histopathological examination confirmed a diagnosis of MSEP, showing hyperplastic duodenal mucosa with submucosal expansion composed of fibroconnective tissue and prominent dilated lymphovascular channels, without evidence of inflammation or neoplastic changes (Figure 3). Histopathological examination confirmed a diagnosis of MSEP of the duodenum.

Figure 3 Histological section (hematoxylin and eosin staining). A: Low-power view demonstrating the overall architecture of the polyp; B: Higher magnification highlighting architecturally normal small intestinal mucosa (black arrows) overlying a core of submucosa containing abundant adipose tissue (blue arrows) with submucosal vessels (green arrows). No significant inflammation is seen.

TREATMENT

Given the lesion’s significant enlargement to approximately 10 cm over 15 months and the absence of adenomatous or suspicious features on endoscopic imaging, endoscopic submucosal dissection was selected as the treatment approach to achieve complete en bloc resection. The procedure was performed successfully without immediate complications.

OUTCOME AND FOLLOW-UP

The patient recovered uneventfully after the procedure. No complications such as bleeding or perforation occurred. Surveillance gastroscopy performed one year after resection revealed no evidence of residual or recurrent polyps.

DISCUSSION

We herein reported a rare case of unusually rapid growth of a duodenal muco-submucosal elongated polyp. While MSEPs are increasingly recognized in the colon, including the rectum, with reported sizes ranging from 7 mm to 150 mm (mean 28 mm), their occurrence in the small intestine, particularly the duodenum, remains uncommon and sparsely documented in the literature[2,3]. To date, there are 11 published articles in the PubMed database reporting this type of lesion, the majority of which originate from Asia, particularly Japan, and are summarized together with the present case in Table 1[2,3,9-16]. The median age among reported cases was 63 years (range 20-78), with 9 of 11 patients being female. Eight polyps were located in the duodenum and six in the jejunum. The median major-axis length of EMSEPs was 45 mm (range 17-125 mm). The primary clinical manifestations of MSEPs in the small intestine include hemorrhage, anemia and intussusception. All cases that underwent surgical management had lesions situated in the jejunum. Notably, our case was distinguished by exceptionally rapid enlargement in only 15 months, a feature rarely described in the literature.

Table 1 Reported muco-submucosal elongated polyps occurring in the small intestine.

Ref.	Country	Age (year)	Sex	Location	Size (mm)	Symptoms	Therapy
Ezoe et al[9]	Japan	72	F	Duodenum	48	None	Endoscopic treatment
Ezoe et al[9]	Japan	56	F	Duodenum	17	None	Endoscopic treatment
Ezoe et al[9]	Japan	70	F	Duodenum	17	None	Endoscopic treatment
Sugimori et al[10]	Japan	53	M	Proximal jejunum	118	Melena	Endoscopic treatment
Kim et al[11]	Korea	58	F	Duodenum	50	Postprandial discomfort	Endoscopic treatment
Nishimura et al[12]	Japan	70	F	Duodenum	70	Melena	Endoscopic treatment
Tan et al[3]	Singapore	55	F	Duodenum	40	Postprandial discomfort	Endoscopic treatment
Tan et al[3]	Singapore	70	M	Duodenum	22	Reflux symptom	Endoscopic treatment
Shimamura et al[13]	Japan	67	M	Proximal jejunum	32	Melena	Endoscopic treatment
Shimamura et al[13]	Japan	64	M	Proximal jejunum	20	Melena	Endoscopic treatment
Okamura et al[2]	Japan	78	F	Proximal jejunum	125	Melena	Surgical resection
Kikuchi et al[14]	Japan	46	F	Proximal jejunum	60	Abdominal pain	Surgical resection
O'Morain et al[15]	Ireland	62	M	Duodenum	42	Abdominal pain	Endoscopic treatment
Taniguchi et al[16]	Japan	20	F	Upper jejunum	55	Abdominal pain	Surgical resection
Our case	China	64	F	Duodenum	90	Postprandial discomfort	Endoscopic treatment

F: Female; M: Male.

The exact pathogenesis of these polyps remains unclear. It is hypothesized that the edematous, loose connective tissue within the submucosal layer forms protrusions that gradually elongate under the influence of persistent intestinal peristalsis. This theory is partly supported by the observation that such polyps, including-colonic muco-submucosal elongated polyps (CMSEPs), tend to arise in bowel segments with relatively active peristaltic movement.

The differential diagnosis of MSEPs includes other enteric lesions with similar endoscopic appearances, most notably prolapsing mucosal folds related to prolapse-induced polyps and filiform polyps found in inflammatory bowel disease (IBD). Prolapse-induced polyps are commonly associated with conditions like diverticular disease and are believed to develop from a combination of venous congestion and mucosal redundancy caused by intestinal contractions. They are known by various names, such as inflammatory cloacogenic polyps and inflammatory “cap” polyps, but all share similar histopathological features[17]. Endoscopically, these prolapse-induced polyps are usually broad-based and lack the slender worm-like form seen in CMSEPs[18]. Histologically, these lesions are characterized by marked inflammatory changes, mucosal erosions (sometimes with a fibrin cap), fibromuscular obliteration of the lamina propria, and crypt architectural distortion with serration.

Filiform polyps are thin, finger-like projections believed to arise as a reparative response to repeated cycles of ulceration and healing, typically associated with IBD. Unlike CMSEPs, filiform polyps are typically multiple, often forming clusters, and can develop into large tumor-like masses known as giant filiform polyposis[19].

The presence of normal mucosa in CMSEPs can lead to diagnostic confusion with hamartomatous polyps. Like CMSEPs, they are composed histologically of normal mucosal and submucosal components. However, hamartomatous polyps typically exhibit a distorted architectural pattern and a more spherical shape. Solitary Peutz–Jeghers-like hamartomatous polyps are distinguished by their characteristic multilobulated gross appearance and histological features, including arborizing smooth muscle bundles and hyperplastic epithelial elements[20].

Endoscopic ultrasound enables visualization of the mucosal and submucosal architecture of the polyp, with characteristic microcystic features aiding diagnosis and distinguishing MSEPs from other submucosal lesions[21].

Although intervention is generally reserved for symptomatic patients, the potential for complications such as intussusception[5], diverticulitis[6], and non-polypoid neoplasia[7,8]-as suggested in case reports-warrants consideration of endoscopic resection even in those without symptoms.

Notably, compared to previously reported cases, our case demonstrated an unusually rapid increase in polyp size-from approximately 1.5 cm to 10 cm-within just 15 months. Such accelerated growth has not been clearly documented in the existing literature and represents a rare clinical behavior for MSEPs, which are typically considered slow-growing and indolent. This observation underscores the need for regular surveillance even in lesions initially thought to be benign, as dynamic morphological changes may alter clinical decision-making and warrant timely intervention.

CONCLUSION

In conclusion, this case enriches the current understanding of duodenal MSEPs by illustrating their potential for unexpected behavior. Clinicians should remain vigilant when monitoring such lesions, as changes in size or morphology-even in the absence of symptoms-may necessitate re-evaluation of management strategies.

ACKNOWLEDGEMENTS

The authors express their sincere gratitude to the participants for their assistance and willingness to be part of this study.