Discussion
Umbilical discharge is common in children and usually due to infection. An underlying congenital anomaly should be investigated, such as umbilical hernia, urachal remnant and OMD remnant. OMD remnant, with a prevalence of only 2%, varies from patent OMD, to cysts, fibrous cords connecting the umbilicus to the distal ileum, granulation tissue at the umbilicus, umbilical hernias, and diverticulum of Meckel [
13]. OMD remnant causes umbilical discharge generally through patency between the gut and umbilicus, rarely due to the presence of heterotopic pancreas.
First described in 1729 by Jean-Schultz, heterotopic or ectopic pancreas is defined as the presence of an abnormally located focus of normally developed pancreatic tissue outside the boundaries of the orthotopic pancreas, without anatomical or vascular connections. It is considered as the second most common congenital anomaly of the pancreas, after divisum. The prevalence has been reported to be 0.55 to 13.7% at autopsy and 0.2% at laparotomy [
14]. It is most often discovered in fifth and sixth decades of life, and infrequently reported in the pediatric age group [
11]. Seventy to 90% of heterotopic pancreas occurs in the upper gastrointestinal tract, while it can also be found anywhere [
15]. It usually presents as an asymptomatic incidental finding, but it can cause symptoms as well depending on the size, location and pathological changes.
Umbilicus is an uncommonly reported location for heterotopic pancreas. Only 18 cases were found at the umbilicus, including ours (Table
1). The age ranges from newborn to 60 years old. Fifteen of them were below 2 years old, one adolescent, one young adult and only one elderly. Fourteen were male and 3 were female, one not indicated in the report. Most of them presented with umbilical discharge. Five were described to have coexisting small intestinal and/or gastric mucosa, which suggested the presence of heterotopic pancreas in the OMD remnant.
Table 1. Summary of cases of heterotopic pancreas at the umbilicus
1 | 12 years/F | N/A | N/A | N/A | Wright (1900), cited by Harris et al. [ 1] |
2 | 22 years/M | Y | N/A | N/A | Trimingham (1943), cited by Harris et al. [ 1] |
3 | Newborn | N | I | N/A | |
4 | 6 months/M | N/A | N/A | N/A | Steck and Helwig (1964), cited by Avolio et al. [ 4] |
5 | 13 months/M | Y | N/A | N/A | Caberwal et al. (1977) [ 2] |
6 | 60 years/M | N | II | Small intestinal mucosa | |
7 | 8 months/M | Y | N/A | N/A | |
8 | 15 months/M | Y | N/A | N/A | |
9 | 6 months/M | Y | N/A | N/A | Perez-Martinez et al. (1999) [ 5] |
10 | 3 months/M | Y | I | N/A | |
11 | 7 weeks/M | Y | I | N/A | |
12 | 2 years/M | N/A | N/A | N/A | |
13 | 8 days/M | Y | I | Acute haemorrhage | |
14 | 18 months/M | Y | N/A | Gastric mucosa | |
15 | 2 years/M | N | N/A | N/A | Abdelgabar et al. (2013) [ 10] |
16 | 2 years/M | Y | I | Small intestinal mucosa and gastric mucosa | Sharma et al. (2013) [ 11] |
17 | 3 months/F | Y | I | Small intestinal mucosa | |
18 | 3 months/F | Y | I | Small intestinal mucosa | Present case |
The Heinrich system is frequently used to classify heterotopic pancreas into 3 types. Type 1 contains acini, islets and ducts. Type 2 contains acini and ducts only, but no islets. Type 3 contains ducts alone [
16]. In the described heterotopic pancreas at the umbilicus, type 1 was most commonly encountered.
Several mechanisms have been proposed for the pathogenesis of heterotopic pancreas, including the misplacement of embryonic tissue developing into pancreatic tissue, the metaplasia of endodermal tissue that migrates to the submucosa during embryogenesis into pancreatic tissue, and the differentiation of totipotent endodermal cells lining the gut or OMD into pancreatic tissue [
12].
Heterotopic pancreas can manifest clinically with diseases of the pancreas, such as pancreatitis, pancreatic cyst, neuroendrocrine tumour and pancreatic carcinoma [
17]. The incidence of malignant transformation is reported as high as 12.7% in a Japanese series [
18]. Therefore, follow up is suggested if incompletely excised, although heterotopic pancreas itself is a benign condition. In this case, heterotopic pancreatic tissue was present at the cauterized edge of the specimen, which raised the possibility of residual pancreatic tissue left behind. Till now, on the follow-up of the patient, her umbilical redness resolved. Limited local excision appeared to be a safe and adequate procedure in the current setting.
Conclusions
In conclusion, heterotopic pancreas at the umbilicus is an uncommon condition, predominantly occurring in infants despite a wide range of ages. It demonstrates a high male to female ratio, frequent association with omphalomesenteric duct remnant and presentation of umbilical discharge. Radiology may not be helpful. Diagnosis is usually straight forward on the histologic evaluation of resection specimen, complemented with immunohistochemistry. Awareness of this finding in biopsy aids in the suitable treatment decisions for the patient.
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