Perianal Bronchogenic Cysts: A Rare Case Report

ABSTRACT

To the best of our knowledge, we report a rare case of a multilocular perianal bronchogenic cyst, confirmed by ciliated epithelium and cartilage. Clinicians should consider this diagnosis for atypical perianal masses and ensure complete excision with long‐term follow‐up.

1. Introduction

Bronchogenic cysts (BCs) are congenital foregut‐derived anomalies that typically develop in the mediastinum or along the tracheobronchial tree [1, 2]. They originate during Weeks 3–7 of gestation due to abnormal budding or branching of the primitive foregut's tracheobronchial tree [3, 4], with most cases located in the posterior mediastinum [5, 6]. Rare ectopic occurrences in the retroperitoneum or pelvis [7, 8] may result from premature separation and migration of tracheobronchial remnants prior to pleural fusion [3, 8]. Most cysts ultimately present with symptoms of mass effect, drainage, infection, or evolve into complex cysts [9]. Previous reports indicate that cutaneous manifestations of BCs are rare across all age groups, particularly in adults. When skin manifestations do occur, they often appear above the abdomen [10]. However, occurrences in the perianal region are even rarer; as of 2025, only three cases, including ours, have been reported [11]. In this study, we report a rare case of a multilocular perianal bronchogenic cyst in a 22‐year‐old male. Perianal bronchogenic cysts are a rare developmental anomaly requiring diagnosis through clinical examination combined with imaging and pathological assessments, usually managed via surgical intervention. This report provides significant epidemiological evidence for the rare occurrence of anal bronchogenic cysts. The case report discusses a rare instance of an anal bronchogenic cyst, exploring its clinical manifestations, diagnostic challenges, and management, supplemented by a literature review.

2. Case History

The patient, a 22‐year‐old unmarried male, had a 1.5‐year history of an asymptomatic anal mass. He recently presented with a 2‐day history of a protruding anal mass accompanied by hematochezia and was admitted on June 20, 2024. Preoperative pelvic CT imaging was performed to evaluate the lesion. Axial and sagittal views revealed a well‐defined cystic lesion within the subcutaneous tissue of the perianal region, confined to the local area without extension into the pelvic cavity or involvement of adjacent organs (Figure 1A,B). This finding supported the clinical impression of a localized benign cystic mass and guided the surgical approach. He was afebrile and exhibited no signs of systemic infection. This clinical study was approved by the Ethics Committee of Shanghai Baoshan Luodian Hospital (LDYY‐KY‐2025‐28), and the patient provided written informed consent.

FIGURE 1.

Preoperative pelvic CT imaging. (A) Axial CT showing a cystic lesion (arrow) within the subcutaneous tissue. (B) The sagittal view shows the cyst confined to the perianal region, with no other cystic lesions in the pelvic cavity. The red arrow represents the iconic anatomical organ.

3. Differential Diagnosis, Investigations and Treatment

The differential diagnosis for perianal cystic lesions includes perianal bronchogenic cysts, epidermoid cysts, dermoid cysts, caudal cysts, rectal duplication cysts, anal glandular cysts, and perianal abscesses.

Table 1 summarizes the abnormal laboratory values, along with their corresponding reference ranges and clinical significance. The pattern of liver enzyme elevation (alanine aminotransferase [ALT] and gamma‐glutamyl transferase [GGT]) suggests hepatic involvement, though without clinical symptoms this was deemed non‐urgent.

TABLE 1.

Clinical Summary of the Patient.

Category	Detailed findings
Demographics	22‐year‐old male, no past medical history
Presenting symptoms	Protruding anal mass (1.5 years)Acute hematochezia (2 days)
Physical examination (lithotomy position)	Inspection: 12 o'clock: Soft, movable mass, skin pigmentation (Figure 2A). 5 & 9 o'clock: Thrombosed hemorrhoids (tender+). Rectal palpation and digital examination: Scar‐like fibrotic thickening in the perianal region (clinically assessed by inspection and palpation). 7/11 o'clock: Mucosal congestion (Figure 2A). 6 o'clock: Hard anal papilla (Figure 2A).
Laboratory results	Blood routine: WBC 6.9 × 109/L, N% 68.7%, RBC 5.28 × 1012/L, Hb 163 g/L. Liver function: ALT 74 U/L (↑, normal 9–50). GGT 84 U/L (↑, normal 10–60). Total bilirubin 26.2 μmol/L (↑, normal 3–21). Direct bilirubin 4.7 μmol/L (normal: 0–5 μmol/L). Indirect bilirubin 21.5 μmol/L (normal: 3–17 μmol/L; mild elevation). Total protein 71 g/L (normal: 65–85 g/L). Renal function: UA 515 μmol/L. Coagulation: PT 11.00 s, INR 0.91, APTT 28.8 s, FIB 2.04 g/L, TT 18.70 s, AT‐III 96.7%, FDP 1.0 mg/L
Imaging findings	Ultrasound: Normal abdominal viscera. Pelvic CT: A solitary, well‐circumscribed cystic lesion at the 12‐o'clock position within the subcutaneous tissue. (Figure 1A,B) Mild fatty liver Pulmonary fibrous nodules
Other investigations	ECG: Sinus bradycardia with arrhythmia
Preliminary diagnosis	Mixed hemorrhoids, thrombotic external hemorrhoids, anal papilla hypertrophy
Clinical timeline	Admission: June 20, 2024 | Surgery: June 21, 2024 | Discharge: July 11, 2024 | Latest Follow‐up: April 21, 2026 (No recurrence at 22 months)

Abbreviations: APTT, activated partial thromboplastin time; AT‐III, antithrombin III; ECG, electrocardiogram; FDP, fibrinogen degradation products; FIB, fibrinogen; INR, international normalized ratio; PT, prothrombin time; TT, thrombin time; UA, uric acid.

On June 21, 2024, the patient underwent hemorrhoidectomy combined with thrombotic hemorrhoid excision and anal papilla resection under intravenous anesthesia. With the patient in the lithotomy position, a soft, oval‐shaped mass was identified at the 12 o'clock perianal region, with a smooth surface, no tenderness, and measuring approximately 3 cm × 4 cm × 3 cm (Figure 2A). A subsequent 1‐cm linear incision at the 12 o'clock position drained approximately 10–15 mL of this thick, odorless fluid (Figure 2B) [11]. This discolored fluid suggests two underlying pathological processes: Chronic microhemorrhages from cyst wall vasculature can lead to hemosiderin deposition, producing characteristic chocolate‐colored fluid. Bronchogenic cysts often contain mucinous secretions that oxidize over time, similar to the chocolate‐colored fluid described in thoracic bronchogenic cysts. The cyst was carefully dissected from surrounding adipose tissue using electrocautery and removed en bloc without rupture. The intact specimen was sent for histopathological evaluation. Postoperatively, the wound healed well, with good granulation tissue growth, a firm texture, minimal oozing of blood, and a red coloration (Figure 2C).

FIGURE 2.

Representative images before and after surgery for a perianal bronchogenic cyst. (A) Preoperative appearance of the cyst, smooth, and freely movable mass. Thrombosis at 5 o'clock and 9 o'clock positions, with hard texture and significant tenderness (+). Digital rectal examination: Mucosal congestion and swelling at 3, 7, and 11 o'clock positions with soft texture, no blood on the glove. At 6 o'clock position, the anal papilla was hard, and fecal masses were palpable. (B) During the procedure, a soft, smooth, non‐tender oval mass measuring 3 × 4 × 3 cm was identified at the 12 o'clock position. Following local anesthesia, a 1‐cm incision was made, draining 10–15 mL of thick, chocolate‐colored fluid (white arrow). (C) Postoperative appearance of the wound after hemorrhoidectomy, thrombosed hemorrhoid excision, and anal papilla resection; the wound healed well with good granulation tissue, a relatively firm texture, minimal oozing, and a rosy color.

4. Conclusion and Results

Gross examination of the excised specimen revealed a multilocular cystic structure containing three distinct cavities filled with chocolate‐colored fluid exudate. Histopathological results (H&E staining) showed that the cyst cavities were lined with pseudo‐stratified ciliated columnar epithelium (Figure 3A,C). The wall contained glandular structures and smooth muscle (Figure 3B), leading to a diagnosis of bronchogenic cyst. Additionally, the cyst in this report exhibited areas of squamous metaplasia, which is a standard reactive change of bronchial epithelium. The pathological diagnosis (Pathology No. 2422853) indicated the presence of external hemorrhoids accompanied by the formation of a perianal bronchogenic cyst. We acknowledge that the absence of immunohistochemical staining (e.g., CK7, TTF‐1, CDX2) constitutes a limitation in our study, as the scant tissue from the small core biopsy was entirely utilized for diagnostic H&E staining.

FIGURE 3.

Pathological images of perianal bronchogenic cyst tissue (HE staining). (A) The circular area marked by arrows represents the columnar epithelium, glandular structures, and smooth muscle of a bronchogenic cyst (Diagnostic markers), scale bar = 1 mm. (B) High‐power image from the red box in Figure A, showing a cyst cavity lined by pseudostratified ciliated columnar epithelium (white arrow), with glandular structures and smooth muscle in the wall (black arrow), scale bar = 200 μm. (C) Pathological staining images of other tumor tissues, with the circular area indicated by the white arrows representing the bronchogenic cyst, scale bar = 1 mm.

Postoperatively, the patient had an uneventful recovery and was discharged on July 11, 2024 (20 days post‐surgery). The patient was followed up 1 month after surgery, and the skin manifestation of the cyst had resolved completely, with no tenderness, bleeding, swelling, or other signs of inflammation. To ensure rigorous long‐term surveillance, a subsequent telephone follow‐up was conducted on April 21, 2026 (22 months postoperatively), which confirmed that the patient remained completely asymptomatic with no signs of local recurrence. The timeline of the case is as follows.

4.1. Timeline of the Case

• Past 1.5 years: The patient noted an asymptomatic perianal mass.

• June 18, 2024: Acute protrusion of the mass with hematochezia.

• June 20, 2024: Hospital admission for evaluation.

• June 21, 2024: Surgical excision of the multilocular cyst.

• July 11, 2024: Discharged from the hospital (postoperative Day 20) following satisfactory wound healing.

• July 21, 2024 (1‐month follow‐up): Complete resolution of clinical signs and symptoms.

• April 21, 2026 (22‐month follow‐up): Telephone follow‐up confirmed the patient remains asymptomatic with no evidence of recurrence.

5. Discussion

From an embryological perspective, bronchogenic cysts are believed to originate from abnormal budding of the primitive foregut, essentially arising from lung embryonic tissue during early embryogenesis [2]. Two main hypotheses have been proposed to explain their ectopic occurrence in atypical sites like the perianal region. The first hypothesis suggests that a portion of the developing tracheobronchial tree becomes sequestered and aberrantly migrates caudally along the midline prior to pleural fusion [1, 3]. Alternatively, the in situ development hypothesis posits that local cutaneous perianal tissues undergo abnormal heterotopic differentiation or metaplasia into respiratory epithelium without a migrating bronchial remnant [1, 12]. Despite the paucity of definitive direct evidence [13], these theories offer a plausible theoretical framework for understanding how a bronchogenic cyst could appear in a perianal location, accounting for both the aberrant migration and anomalous differentiation potentially responsible for our case. Microscopically, bronchogenic cysts typically consist of a unilocular cystic structure lined by pseudostratified ciliated columnar epithelium [14]. The cyst wall often contains components characteristic of bronchial tissue, such as bronchial glands, smooth muscle, hyaline cartilage, and seromucous glands [15, 16]. Bronchogenic cysts are most commonly found in the mediastinum of the thoracic cavity [6]. Generally, they are small and asymptomatic, though occasionally they can cause complications such as infection, acute hemorrhage, or compression of adjacent organs [9]. Their reported frequency by location is highest in the intrathoracic region and lowest cutaneously [1, 17, 18]. Cutaneous or subcutaneous bronchogenic cysts are exceedingly rare, mostly noted at birth or in early childhood [12, 19]. Approximately 30% occur at the suprasternal notch, followed by the anterior neck, scapular area, and presternal chest. To date, literature on cutaneous bronchogenic cysts in the perianal region is exceedingly sparse, with very few documented cases [11], underscoring the extreme rarity of our patient's presentation.

Further investigation into embryological development is needed to clarify why bronchogenic cysts virtually never occur in perianal skin. In our case, the cyst's histopathology was consistent with a bronchogenic origin. However, departing from the typically unilocular presentation, our case uniquely presented as a multilocular cystic structure containing three distinct cavities. The definitive diagnosis was established by the classic morphology: the distinct cavities were lined by ciliated pseudostratified columnar epithelium, and the wall contained smooth muscle and glands, in line with previously reported cases. Notably, focal areas of squamous metaplasia were observed in the cyst lining—a common reactive change to chronic irritation or inflammation, which does not detract from the diagnosis. By reviewing other reported bronchogenic cysts in unusual locations and comparing them with this perianal case, we found that our case shares the characteristic histological features despite its atypical location. In conjunction with the related literature, our report underscores the unique multilocular nature of this perianal bronchogenic cyst and contributes to the characterization of this rare entity.

Clinical insights from this case center on two main aspects: diagnostic challenges and patient management. In terms of diagnostic challenges, patients with bronchogenic cysts often remain asymptomatic, making diagnosis in rare locations difficult, which can lead to misdiagnosis as common perianal lesions (such as hemorrhoids or anal fistulas). Existing case reports indicate that perianal bronchogenic cysts are usually located in the subcutaneous tissue around the anus. Previous literature has reported these as solitary [11], while our case uniquely presents as a multilocular cyst. To our knowledge, this is the first report highlighting a multilocular presentation in a perianal bronchogenic cyst, which may reflect complex abnormal budding during its embryological migration. The palpable soft tissue masses can compress surrounding anal tissues, resulting in pain during defecation and hematochezia. Additionally, there is a risk of infection within the cysts, potentially leading to symptoms such as the discharge of chocolate‐colored fluid. Diagnosis is typically made through imaging studies such as ultrasound, CT scans, and MRI, combined with physical examination and medical history. Confirmation of the cyst's origin and type is achieved through biopsy or pathological examination after surgical removal. It is emphasized that when rare tumors are found in the perianal area, bronchogenic cysts should be considered in the differential diagnosis, with imaging and pathological analysis playing crucial roles in confirmation. Clinically, our patient presented with a well‐circumscribed, painless, perianal mass without any signs of inflammation, sinus tract, or external openings—findings which are atypical for pilonidal disease. There was also no evidence of hair, debris, or recurrent infection, which are commonly associated with dermoid or pilonidal cysts. Importantly, no skin adnexal structures such as hair follicles or sebaceous glands (as seen in dermoid cysts) were identified. These combined clinical and histological features support the diagnosis of a perianal bronchogenic cyst and effectively exclude dermoid, epidermoid, and pilonidal cysts. In the context of a broad differential diagnosis, immunohistochemical analysis for molecular diagnosis can provide valuable reference information. Reports of unique molecular features of bronchogenic cysts from other locations indicate that the majority express CK7 while not expressing CK20 [20, 21] or CDX‐2 [21]. TTF‐1 (a transcription factor present in the lung and thyroid) is significant in diagnosing bronchogenic cysts, as its positive expression can aid in confirming the pulmonary characteristics of tumors or cysts through a molecular pathology perspective [22], assisting in distinguishing bronchogenic cysts from other types of cysts or tumors, thereby improving diagnostic accuracy. The combination of CK7 and CK20 helps narrow the differential diagnosis and supports the pulmonary origin of these tumors. Thus, the combination of CK7+, CK20− and TTF‐1+ is of considerable reference value in diagnosing PBCs [21].

As summarized in Table 2, our case appears to be the first documented report highlighting a multilocular (three‐cavity) presentation of a perianal bronchogenic cyst. While the multilocular nature of this cyst remains an unusual finding, it is plausible that it shares a similar underlying embryological mechanism to solitary lesions, though this remains entirely speculative. Complete excision remains the definitive treatment.

TABLE 2.

Comparative summary of reported perianal bronchogenic cyst cases, highlighting its multilocular presentation.

Case	Source (year)	Age/sex	Lesion number	Location & size	Histology (epithelium)	Key IHC findings	Follow‐up
1	Liu et al. [11]	53/M	Solitary	Right perianal, 3.5 × 4.0 × 4.0 cm	Pseudostratified columnar	CK7+, TTF‐1‐, CK20‐, CDX2‐	No complications
2	Liu et al. [11]	59/M	Solitary	Right perianal, 3.0 × 4.0 × 4.5 cm	Ciliated columnar	CK7+, TTF‐1+ (rare), CK20‐, CDX2‐	No complications
3	Present Case	22/M	Single, multilocular (three cavities)	Perianal (12 o'clock), ~3 × 4 × 3 cm	Pseudostratified ciliated columnar	Not performed	Asymptomatic at 1 month; no recurrence at 22 months

In the treatment and management of perianal bronchogenic cysts, preventing the occurrence of complications remains a critical consideration during the treatment process. Potential complications from untreated or improperly treated cases, such as infections and malignancies, are concerning; existing cases show that cysts have exhibited chocolate‐colored purulent fluid, indicating a potential risk for infection or malignancy [23]. Furthermore, cysts may present symptoms related to mass effect or evolve into complex cysts, necessitating the complete removal of the cyst wall during initial surgical procedures. The treatment strategy for perianal bronchogenic cysts is similar to that of bronchogenic cysts in other rare locations, with surgery being the optimal treatment method. According to existing case reports [11], perianal bronchogenic cysts are typically benign lesions, and surgical excision is the most effective approach for achieving a definitive diagnosis, alleviating patient discomfort, and reducing the likelihood of malignant transformation. Although the recurrence rate of cysts is low, regular follow‐up is essential to monitor for recurrence. In our case, initial follow‐up at 1 month post‐surgery revealed that the patient remained asymptomatic. To address the relatively short initial observation period, an extended follow‐up at 22 months post‐surgery was conducted, confirming the durable absence of clinical recurrence.

Author Contributions

Dongqin Wang: investigation, writing – original draft. Zhiqiang Yuan: validation, writing – review and editing. Chunxin Liu: investigation. Yingnan Yang: data curation, writing – review and editing. Ya Lv: data curation, writing – review and editing. Hao Huang: data curation, writing – review and editing. Yu Chen: conceptualization.

Funding

This study was supported by Shanghai Baoshan District Science and Technology Commission Research Project (2024‐E‐49), the Key Medical Specialty and Characteristic Brand Development Project of Baoshan District (BSZK‐2023‐BZ03), Chen Yu Baoshan District Famous Traditional Chinese Medicine Inheritance Studio (BZMZYGZS‐2024‐08), and the Research Project of Shanghai Baoshan Luodian Hospital (23‐B‐1).

Consent

Written informed consent was obtained from the patient.

Conflicts of Interest

The authors declare no conflicts of interest.

Data Availability Statement

The data that support the findings of this study are available on request from the corresponding author. The data are not publicly available due to privacy or ethical restrictions.