Giant mucocele of the colon at the distal stump due to low-grade mucinous neoplasia
© The Author(s). 2016
Received: 23 May 2016
Accepted: 2 September 2016
Published: 27 October 2016
We present the first ever report on a colonic mucocele observed at the distal stump of a transverse loop colostomy caused by neoplasia. A 37-year-old female consulted us because of abdominal pain and vomiting caused by cystic lesions in the upper left abdominal quadrant. A preoperative checkup revealed no sign of neoplastic lesions; however, tumor resection was performed because of the symptoms. The tumor was a mucocele of the distal stump of the transverse colon with obstruction interposed between the mucocele and stoma. Pathological diagnosis was low-grade adenoma; however, it appeared like low-grade mucinous neoplasia of the appendix rather than a normal colonic adenoma. The neoplasia existed in the transitional segment between obstruction and dilatation. As this is the first case of colonic mucocele caused by mucinous neoplasia, no definite consensus for diagnosis and treatment exists. With reference to low-grade mucinous neoplasia, we propose that complete surgical resection be performed for diagnosis and a favorable outcome.
Mucocele of the colon is a rare clinical manifestation, with only few reports being available. The etiology of colonic mucocele is yet to be unraveled, and no pathological features have been described so far. Here, we describe the first case of colonic mucocele caused by a low-grade colonic neoplasia, providing an insight on the clinical and pathological etiology of colonic mucocele.
The patient was discharged on the 12th postoperative day; the serum CEA level decreased to 3.3 ng/mL 1 month after the surgery.
Appendiceal mucocele, which is caused by the accumulation of mucin due to appendiceal obstruction, is a well-known type of appendiceal tumor, accounting for 0.1–0.3 % of all appendectomies . They are often asymptomatic and incidentally found during surgery or diagnostic imaging for other diseases. Conversely, colonic mucocele is an extremely rare clinical manifestation, with only five cases reported so far, all of which were symptomatic because of large-sized lesions, and most of which developed following colonic surgery. Two cases developed upon diverting colostomy, with mucinous tumors developing distal to the stoma [2, 3]. The other two cases developed after ileosigmoid bypass as palliative surgery for malignant colonic obstruction, with the mucinous cyst developing at the isolated segment of the colon [4, 5]. In all cases, the unused bowel segment was the predilection site of mucin accumulation, similar to the present case. Leaving a bowel segment unused is a risk factor for the development of colonic mucocele.
The existence of neoplastic lesions similar to low-grade appendiceal mucinous neoplasia was a striking feature in our case. Low-grade mucinous neoplasia is often found in appendiceal mucocele; however, no such neoplasia has been reported so far in a patient with colonic mucocele. We hypothesized on how neoplasia could be related to the etiology of the mucocele of the present case. First, atrophic changes developed in the colon distal to the site of loop colostomy, resulting in narrowing of the luminal diameter. Even at this point, the intraluminal space would be preserved for continuous discharge produced by the distal stump. Subsequently, however, the neoplastic lesion produced more amounts of viscous mucin which then pass the stricture where the mucocele developed. This hypothesis presents a possible explanation for why the patient developed mucocele a long time after colostomy. Hence, the development of neoplasia was the primary cause of the mucocele.
We did not obtain definitive diagnostic results prior to the surgery. Although percutaneous aspiration biopsy is potentially accompanied with complications like hemorrhage or tumor dissemination, we did not obtain informative histological findings even after this procedure. No abnormal accumulation was found by positron emission tomography, and signs of neoplasia were not identified by colonoscopy. This diagnostic uncertainty was reminiscent of the challenges encountered when diagnosing appendiceal mucocele .
Because this is the first case of colonic mucocele accompanied by low-grade mucinous neoplasia, any consensus regarding appropriate operative procedures does not currently exist. According to the WHO classification, low-grade appendiceal mucinous neoplasia is a malignant tumor, and therefore, complete surgical resection is suggested. Hence, complete surgical resection appeared appropriate in the present case. Moreover, given the condition that it is difficult to obtain a definitive pathological diagnosis preoperatively, we should consider surgery for colonic mucocele even in the absence of proof of dysplasia. The postoperative course of appendiceal mucocele is typically characterized by recurrence presenting as intraperitoneal myxoma, and medical follow-up by CT scan every 6–12 months is recommended. With reference to this recommendation, we intend to perform a periodic follow-up of the colonic mucocele.
In conclusion, we demonstrated colonic mucocele caused by low-grade mucinous neoplasia. Although standardized diagnostic criteria and surgical procedures do not exist as yet, complete resection for colonic mucocele to avoid rupture and unfavorable clinical outcomes should be performed.
We obtained written informed consent for publication from the patient.
All the authors listed above contributed to this manuscript. All authors read and approved the final manuscript.
The authors declare that they have no competing interests.
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