Perforated ascending colonic mucinous adenocarcinoma with a subserosal mucin pool presenting as a giant cystic lesion: a case report

Abstract

Introduction and importance:

Mucinous adenocarcinoma (MAC) represents 10–20% of colorectal cancers and is characterized by abundant extracellular mucin pools. We report an unusual case of ascending colonic MAC with a giant subserosal mucin pool presenting as a cystic lesion, complicated by perforation during bowel preparation.

Case presentation:

An 83-year-old woman presented with a 14-cm cystic mass in the ascending colon on computed tomography (CT). Approximately 2 hours after starting polyethylene glycol ingestion for colonoscopy, she developed acute abdominal pain. CT revealed pneumoperitoneum, prompting emergency laparotomy. Intraoperatively, an ascending colonic tumor with an attached 150 × 140 mm cystic lesion containing approximately 1 L of mucin was identified, with a 2-mm perforation in the non-tumorous bowel wall proximal to the tumor. Ileocecal resection with oncologic lymph node dissection and end ileostomy was performed. Histopathology revealed a well-differentiated adenocarcinoma with mucinous components (pT4aN1bM0, Stage IIIC). After completing adjuvant chemotherapy, the patient remains disease-free 2 years after surgery.

Clinical discussion:

The perforation was likely caused by an acute increase in intraluminal pressure due to bowel preparation, combined with functional luminal narrowing resulting from extrinsic compression by the giant cystic lesion. Because the perforation occurred proximal to the tumor rather than through the tumor itself, intraperitoneal tumor-cell or mucin spillage may have been minimal.

Conclusion:

MAC with a giant cystic lesion is rare and may predispose patients to perforation during bowel preparation. Careful bowel preparation, close symptom monitoring, and prompt evaluation with timely surgical management are important to avoid life-threatening complications.

Introduction

Colorectal mucinous adenocarcinoma (MAC) is characterized by abundant extracellular mucin pools comprising more than 50% of the tumor volume^[1,2^]. MAC often presents at an advanced stage and is associated with large tumor size, lymph node metastasis, and peritoneal dissemination^[3^]. Perforation is a serious complication of colorectal cancer and is associated with increased morbidity, mortality, and oncologic disadvantage, particularly when tumor cells or mucin are spilled into the peritoneal cavity. Consequently, perforated MAC is associated with higher peritoneal recurrence and poorer prognosis compared to non-mucinous subtypes^[4^].

Here, we report a rare case of ascending colonic MAC with a giant subserosal mucin pool presenting as a cystic lesion, complicated by perforation during bowel preparation. This case is reported in accordance with the Surgical CAse REport (SCARE) guidelines^[5^].

HIGHLIGHTS

• Ascending colonic mucinous adenocarcinoma presents with a giant cystic lesion.

• Perforation occurred during bowel preparation for a colonoscopy.

• The perforation arose in the non-tumorous bowel proximal to the tumor.

• The cystic lesion represented an expanded subserosal mucin pool.

• Careful bowel preparation and prompt evaluation are important in such cases.

Case presentation

An 83-year-old woman presented with a 2-month history of lower abdominal discomfort and 1 week of constipation. She had hypertension, congestive heart failure, cerebral infarction, dyslipidemia, and diabetes mellitus, with no history of abdominal surgery. Her medications included ticlopidine, amlodipine, azosemide, famotidine, and atorvastatin. Physical examination by a local physician revealed a palpable 15-cm abdominal mass. Her height was 149.8 cm, weight was 63.2 kg, and body mass index was 28.1 kg/m². Contrast-enhanced computed tomography (CT) revealed wall thickening of the ascending colon with an adjacent 14-cm cystic low-density mass, without bowel obstruction (Fig. 1A and 1B). Colonoscopy was scheduled as an outpatient procedure.

Figure 1.

Preoperative and emergency CT findings. (A) Initial contrast-enhanced computed tomography (CT) shows a 14-cm thin-walled cystic lesion adjacent to the ascending colon, with homogeneous low-attenuation content and continuity with the colonic wall. The red arrow indicates the junction between the tumor and the cystic lesion. (B) Initial contrast-enhanced CT shows marked thickening of the ascending colonic wall and enlarged regional lymph nodes. The red arrow indicates the continuity between the tumor and the cystic lesion, the yellow circle indicates the tumor location, and the yellow arrow indicates the enlarged regional lymph nodes. (C) Contrast-enhanced CT obtained during the emergency visit shows increased peritumoral fat attenuation, intraperitoneal free air, and ascites, suggesting intestinal perforation. The yellow arrows indicate intraperitoneal free air, and the blue arrow indicates ascites.

Approximately 2 hours after starting oral ingestion of 2L of a polyethylene glycol-based electrolyte lavage solution as a single dose for bowel preparation, containing macrogol, potassium chloride, sodium bicarbonate, sodium chloride, and sodium sulfate, the patient developed severe right lower abdominal pain and was transported to the emergency department. On arrival, her blood pressure was 94/57 mmHg, heart rate was 86/min, body temperature was 36.1°C, and oxygen saturation was 96% on room air. Physical examination revealed rebound tenderness and muscle guarding. Laboratory data showed leukopenia (white blood cell count, 2.7 × 10³/µL), elevated inflammatory markers (C-reactive protein, 2.81 mg/dL; procalcitonin, 90 ng/mL), hypoalbuminemia (2.4 g/dL), and metabolic acidosis (pH, 7.31; HCO₃⁻, 18.6 mmol/L). Serum tumor markers were within normal limits (carcinoembryonic antigen [CEA], 3.4 ng/mL; carbohydrate antigen 19-9 [CA19-9], 15.3 U/mL). CT revealed newly developed diffuse free air and ascites, suggesting bowel perforation (Fig. 1C), prompting emergency laparotomy.

Intraoperatively, an ascending colonic tumor with an attached 15-cm cystic lesion was identified (Fig. 2A). A 2-mm perforation was observed in the non-tumorous bowel proximal to the tumor. Purulent ascites were present without fecal contamination or gross peritoneal nodules. Ascitic fluid cytology was not performed because of the emergency setting and unstable hemodynamics. Given the patient’s unstable hemodynamics, ileocecal resection with D2 lymph node dissection and an end ileostomy was performed (Fig. 2B). The operative time was 148 minutes, with blood loss of 182 mL.

Figure 2.

Intraoperative findings. (A) Laparotomy reveals a giant cystic lesion measuring approximately 14 cm, attached to the medial aspect of the ascending colonic tumor. The cystic lesion is thin-walled and unilocular, and it is directly continuous with the serosal surface of the ascending colon overlying the primary tumor. (B) A 2-mm perforation is identified in the non-tumorous colonic wall proximal to the tumor. Ileocecal resection with D2 lymph node dissection was performed without primary anastomosis because of unstable hemodynamics. The bowel was divided proximally as an end ileostomy and distally as a closed stump. The arrow indicates the resection line.

Postoperatively, the patient was admitted to the intensive care unit (ICU) and managed with mechanical ventilation. Because of septic shock, circulatory support with noradrenaline, vasopressin, and hydrocortisone was required. The Sequential Organ Failure Assessment (SOFA) score peaked at 5 on postoperative day (POD) 1, and the serum lactate level peaked at 1.7 mmol/L on POD 1. Vasopressor requirements peaked at 0.2 μg/kg/min of noradrenaline and 1.8 units/h of vasopressin, and all vasopressors were discontinued by POD 5. Blood cultures obtained on admission and during the postoperative course were negative. Broad-spectrum antimicrobial therapy was administered and adjusted according to the clinical course. The patient was extubated on POD 6, oral intake was resumed on POD 8, and she was transferred from the ICU to the general ward on POD 10. No major complications occurred, and the patient was transferred to a rehabilitation hospital on POD 42.

Gross pathological findings revealed a 70 × 50 mm circumferential ulcerated tumor in the ascending colon and a 150 × 140 mm giant cystic lesion attached to the serosal side (Fig. 3A). The cystic lesion was continuous with the area of serosal invasion and contained approximately 1 L of mucoid fluid, without feces or pus (Fig. 3B). Histologically, the tumor was a well-differentiated adenocarcinoma with mucinous components characterized by abundant extracellular mucin pools containing tumor cells (Fig. 3C and 3D). The cyst wall comprised mainly serosal mesothelial cells and was continuous with the serosal invasion site, suggesting that the subserosal mucin pool formed the cystic lesion (Fig. 3E). The final pathological diagnosis was pT4a, pN1b, cM0, R0, Stage IIIC, with negative lymphovascular invasion, positive perineural invasion, and negative resection margins.

Figure 3.

Pathological findings. (A) Gross examination of the resected specimen shows a circumferential ulcerated tumor measuring 70 × 50 mm in the ascending colon and a giant cystic lesion measuring 150 × 140 mm on the serosal side. (B) The cystic lesion contains approximately 1 L of mucinous fluid. The cyst wall is continuous with the serosal invasion site of the tumor and is covered by serosal mesothelium. (C) Histopathology shows a well-differentiated adenocarcinoma with focal mucinous adenocarcinoma components. Hematoxylin and eosin staining, ×4 magnification. (D) Histopathology shows mucinous adenocarcinoma components with abundant extracellular mucin pools containing tumor cells. Hematoxylin and eosin staining, ×20 magnification. (E) The cyst wall consists mainly of serosal mesothelial cells and is continuous with the site of serosal invasion, suggesting that the subserosal mucin pool formed the cystic lesion. Hematoxylin and eosin staining, ×4 magnification.

Four months after surgery, CT revealed minute nodules suspicious for peritoneal dissemination. The patient subsequently received a 1-year course of adjuvant chemotherapy with a tegafur/gimeracil/oteracil regimen. She tolerated the treatment well, without adverse events. Two years postoperatively, no cancer recurrence was observed, and tumor marker levels remained within normal limits (CEA, 2.5 ng/mL; CA19-9, 16.1 U/mL).

Discussion

The distinctive feature of this case was that ascending colonic MAC formed a giant cystic lesion. Although MAC is characterized by abundant extracellular mucin, its presentation as a giant cystic lesion is rare. In this case, the cystic lesion was continuous with the serosal invasion site and was histologically interpreted as an expanded subserosal mucin pool covered mainly by serosal mesothelium.

This presentation poses a diagnostic challenge, particularly when MAC presents with a giant cystic lesion. Endoscopic biopsy may fail to detect mucinous histology, especially when the mucinous component is deep or predominantly extramural. Therefore, cross-sectional imaging is essential for improving diagnostic accuracy. On CT, mucinous components may appear as low-attenuation areas within a thickened intestinal wall, whereas MRI demonstrates low signal intensity on T1-weighted and high signal intensity on T2-weighted images^[2^]. In the present case, the differential diagnoses included a mesenteric or retroperitoneal cystic tumor, pseudomyxoma peritonei, an appendiceal mucinous neoplasm, a hydatid cyst, an intestinal duplication cyst, and an intra-abdominal abscess^[2,3,6,7^]. However, the direct continuity between the cystic lesion and the thickened ascending colonic wall, regional lymph node enlargement, absence of communication with the appendix, and lack of clinical evidence of abscess favored a diagnosis of colonic malignancy, particularly MAC with a cystic component.

The mechanism of perforation is the central issue in this case. Perforation associated with colorectal cancer is commonly categorized as either perforation through the tumor itself or proximal diastatic perforation secondary to tumor-related obstruction^[8–12^]. In the present case, the perforation occurred in the non-tumorous bowel wall proximal to the tumor, with no tumor cells or diverticulum at the perforation site and no intraoperative fecal contamination. Therefore, the perforation was unlikely to have resulted from direct tumor rupture. Instead, bowel preparation may have acutely increased intraluminal pressure in a bowel segment functionally narrowed by extrinsic compression from the giant cystic lesion. Although no mechanical obstruction was evident on the initial CT, rapid fluid loading and increased bowel motility after ingestion of the lavage solution may have exceeded the tolerance of the proximal bowel under an obstruction-like condition. Although this mechanism remains speculative, the timing of symptom onset after bowel preparation and the pathological absence of tumor at the perforation site are consistent with this mechanism.

The location of the perforation may have favorably influenced the postoperative oncologic outcome. Although ascitic fluid cytology was not performed, the absence of gross mucinous ascites, peritoneal nodules, tumor rupture, and tumor cells at the perforation site suggests that intraperitoneal tumor cell or mucin spillage may have been minimal. This may partly explain the 2-year disease-free course, despite the advanced pT4aN1b Stage IIIC disease and the higher risk of peritoneal recurrence associated with MAC^[2–4^].

Regarding the surgical strategy, current guidelines for perforated colon cancer emphasize both source control and oncologic resection when feasible^[13,14^]. However, primary anastomosis may be inappropriate in patients with septic shock, hemodynamic instability, diffuse contamination, or edematous bowel, and stoma creation or staged surgery should be considered. In the present case, the patient was elderly, had multiple comorbidities, and required vasopressor support for septic shock. Therefore, primary ileocolic anastomosis was avoided, and an end ileostomy was created. D2 lymph node dissection was performed to maintain oncologic adequacy while avoiding excessive surgical invasiveness in an emergency setting^[15^].

From a practical perspective, the present case suggests that bowel preparation should be planned cautiously when colonic MAC with a giant cystic lesion or functional luminal narrowing is suspected. This does not preclude colonoscopy or bowel preparation in such patients; rather, it underscores the importance of individualized preparation strategies, such as adjusting the dose, timing, or rate of ingestion of the lavage solution, performing colonoscopy in an inpatient setting when appropriate, and closely monitoring for acute symptoms after bowel preparation.

This report has several limitations. First, it describes a single case, and longer follow-up is required to determine the oncologic impact of the perforation site. Second, ascitic fluid cytology was not performed; therefore, microscopic intraperitoneal tumor-cell dissemination could not be completely excluded. Third, molecular profiling, including microsatellite instability status and mutations in v-raf murine sarcoma viral oncogene homolog B1 (BRAF)/Kirsten rat sarcoma viral oncogene homolog (KRAS), was not performed. Further accumulation of similar cases is needed to clarify the mechanism, optimal diagnostic strategy, and management of this rare presentation.

Conclusions

We report a rare case of ascending colonic MAC with a giant subserosal mucin pool, presenting as a cystic lesion and complicated by perforation during bowel preparation. In such patients, careful bowel preparation and close symptom monitoring are important, and prompt evaluation and timely surgical management after symptom onset may reduce the risk of life-threatening complications.

Ethical approval

This case report was approved by the Institutional Review Board (2025-4-047).

Consent

Consent for the publication of this case report, along with accompanying images, was obtained from the patient. The consent form will be provided to the editors of this journal upon request.

Sources of funding

This research did not receive any specific grant from any funding agency in the public, commercial, or not-for-profit sectors.

Author contributions

Conceptualization: K.Y. and S.T. Investigation: K.Y. and S.T. Data curation and visualization: K.Y., S.T., and F.F. Resources: K.Y. and F.F. Patient management: K.Y., S.T., and T.N. Supervision: T.N., C.S., and Y.K. Project administration: C.S. and Y.K. Validation: Y.K. Writing-original draft: K.Y. Writing-review and editing: S.T., F.F., T.N., C.S., and Y.K. All authors have read, commented, and approved the final manuscript for submission.

Conflicts of interest disclosure

All authors declare that there are no conflicts of interest.

Research registration unique identifying number (UIN)

Not applicable.

Guarantor

Shingo Tsujinaka.

Provenance and peer review

Not commissioned; externally peer-reviewed.

Data availability statement

The data that support the findings of this study are available from the corresponding author upon reasonable request.

Assistance with the study

None.