Case 3: 13-year-old with an abdominal cystic lesion

Pediatric pathology

Author(s)
Kendall Wilson, MD
Erin Rudzinski, MD

Summary of clinical history
The patient is a 13-year-old female who presented with new acute right upper quadrant pain and nausea. CT imaging revealed a cystic fluid collection measuring up to 4.5 cm in the anterior abdomen, abutting the urinary bladder and ascending toward the umbilicus. Visualization intraoperatively revealed a cystic structure attached to the terminal ileum, which was completely resected.

Gross findings
The ileocecectomy specimen included an intact bulging mass measuring 5.5 x 4.5 x 4.1 cm at the stapled ileal resection margin. Further examination revealed a unilocular cystic cavity filled with white mucoid material with a wall thickness averaging 0.1 cm. The mass was grossly adherent to the terminal ileum.

Microscopic findings
Cystic structure with a discrete muscular lining and an epithelial surface variably composed of nonkeratinizing squamous epithelium and ciliated, pseudostratified columnar epithelium with subepithelial seromucinous glands. 

Click any image for larger version

Figure 1. Histology demonstrates the cyst (bottom) directly attached to the intestinal wall (4x).

Figure 2. Closer view of the cyst shows ciliated pseudostratified columnar epithelium with muscularis mucosa and submucosal mucinous glands (10x). Hyaline cartilage is notably absent. The inset at the top right provides a closer view of the cilia (40x).

Figure 3. A different area of the cyst lining shows non-keratinizing stratified squamous mucosa with a thinned, but distinct underlying muscularis propria(20x).

Figure 4. This area of the cyst lining shows a clear transition between the ciliated pseudostratified columnar epithelium and the stratified squamous mucosa (40x).

Immunohistochemical findings
N/A

Duplication cysts can occur anywhere from the mouth to the anus; however, the most common sites include the ileum, esophagus, and colon. Foregut duplication cysts are thought to occur from abnormal closure or embryologic luminal recanalization/obliteration of the primitive foregut buds. The foregut gives rise to the distal respiratory tract including bronchial and lung tissues, luminal gastrointestinal tissues including esophagus, stomach, duodenum, gallbladder and bile ducts, as well as the pancreas and liver. The most common foregut duplication cysts include bronchogenic and esophageal duplication cysts. Location and type of these cysts depends on embryological stage during which the anomaly occurs.

Bronchogenic cysts develop from an anterior defect in tracheoesophageal separation and aberrant bronchial budding. They demonstrate a ciliated pseudostratified columnar (respiratory) epithelial lining overlying a muscular wall, but also includes intramural cartilage and seromucinous glands indicative of bronchial origin.
Esophageal duplication cysts are typically located in the posterior mediastinum and most commonly present in the 1st year of life due to mass effect/esophageal wall compression. Microscopically, they can be lined by any non-keratinizing squamous (esophageal) or other GI tract-type epithelium. They may also resemble bronchogenic cysts including a ciliated, pseudostratified, columnar epithelial lining and muscular wall; however, they lack cartilage or seromucinous glands.

In this particular case, there is a muscular wall lined by a combination of respiratory mucosa with underlying seromucinous glands as well nonkeratinizing squamous mucosa. Cartilage is not identified. These microscopic findings show histologic overlap with several foregut derived structures, and therefore the most appropriate designation is that of foregut duplication cyst.

Key differential diagnosis

Colonic duplication cyst
These cysts are theorized to form from a similar process as foregut duplication cysts and must be located within or attached to the colon. As opposed to a diverticulum, they do not connect to the bowel lumen. Instead, duplication cysts form a localized mass within the bowel wall or serosa, typically present on the mesenteric aspect of the bowel. They must include intestinal epithelium as well as underlying muscularis propria, including myenteric plexus.

Small intestine duplication cyst
These cysts also likely form from abnormal luminal recanalization and are lined by enteric mucosa, sometimes with gastric or pancreatic epithelium. Like colonic duplication cysts, they duplicate normal bowel histomorphology including a well-defined muscular wall with ganglion cells in the myenteric plexus.

Meckel diverticulum
This entity is the most common congenital GI tract malformation. In contrast to duplication cysts, it arises on the antimesenteric aspect of the bowel. While all three layers of the small bowel wall are present, making it a true diverticulum, the epithelial surface is in continuity with the lumen of the small bowel. Meckel diverticulum is formed by incomplete obliteration and persistence of the vitelline duct. These are usually asymptomatic but may present with intusseception, volvulus, or painless rectal bleeding due to the presence of gastric or pancreatic mucosa. Children diagnosed with a Meckel diverticulum are usually < 2 years old, and it is typically identified within 2 feet proximal to the ileocecal valve.

Urachal cyst
Urachal cysts develop from persistence of the allantois, an embryonic remnant between the umbilicus and the cloaca. When both the umbilical and bladder ends close without complete involution of this tract, it can form a true cyst. Microscopic findings include a lining of benign cuboidal, urothelial, or flattened epithelial cells, sometimes with Intestinal metaplasia.

Mesenteric cyst
This unilocular or multilocular cyst is located on the mesentery and considered a benign proliferation of ectopic lymphatics that do not communicate with the normal lymphatic system.

Enterogenous cyst
These cysts are associated with vertebral anomalies and can be located in the wall of the small bowel, mesentery, posterior mediastinum or rectorectal space. The cyst wall can be lined by respiratory, small intestinal, or gastric epithelium and characteristically exhibits disorganized, irregularly oriented smooth muscle with no nerves or ganglion cells.

References

1. Balakrishnan K, Fonacier F, Sood S, Bamji N, Bostwick H, Stringel G. Foregut Duplication Cysts in Children. JSLS. 2017 Apr-Jun;21(2):e2017.00017. doi: 10.4293/JSLS.2017.00017. PMID: 28642639; PMCID: PMC5464960.

2. Husain Aliya N, Stocker J Thomas, Dehner Louis P. Pediatric Pathology. [Fifth Edition.] Philadelphia, PA: Wolters Kluwer; 2021. [English]

3. Putnam Angelica R, Thompson Karen S. Diagnostic Pathology: Nonneoplastic Pediatrics. [First Edition.] Manitoba, Canada: Amirsys Publishing; 2014. [English]

4. Zoshchuk B, Morisetti M, Beeter MC, Yeh YA. Urachus. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/bladderurachus.html. Accessed July 15th, 2025.