| Abstract|| |
Context: Twelve-year retrospective study of surgically excised umbilical lesions received for histopathology in a pediatric tertiary care hospital. Aims: To study histopathology of the umbilical lesions and review pertinent literature on the embryological basis of these lesions. Subjects and Methods: We reviewed cases of umbilical lesions and classified them as “developmental” and “others.” Developmental cases were sub-classified based on the mechanism as those due to defect in the closure of body wall, defect in the closure of the umbilical ring, persistence of embryonic remnants, or failure of epithelization. Persistent embryonic remnants were subdivided into fistula, sinus, and cyst. Histology of all the cases was studied and the different types of tissue in omphalomesenteric ducts (OMD) remnants were identified. Statistical Analysis Used: Descriptive statistics were used as required. Results: Seventy-one cases in the age range of 1 day to 13 years were studied and male preponderance was noted. The developmental lesions included 4 omphalocele sacs with dense acute inflammation, 2 umbilical hernial sacs with fibrocollagenous tissue, 30 OMD remnants, 10 allantoic duct remnants, 19 umbilical granulomas, and 2 cases showing more than one developmental mechanism. Four cases were classified as “others” including 3 epidermal inclusion cysts and 1 skin tag. Among OMD remnants, sinuses (arising from the distal tract) were found to be the most common. Histological examination of the OMD remnants showed enteric (18), enteric and gastric (5), colonic (4), enteric and colonic (2), and pancreatic and enteric and gastric mucosae (1). Conclusion: Accurate diagnosis is essential for definite treatment of these lesions.
Keywords: Omphalomesenteric ducts remnants, omphalocele sac, umbilicus
|How to cite this article:|
Singaravel S, Yadav PC. Histomorphology of the lesions of the umbilicus: Are we naïve about the navel?. Indian J Pathol Microbiol 2021;64:91-5
| Introduction|| |
Umbilicus or “navel” is a localized, depressed area that marks the previous connection of an individual with their mother during fetal life. The umbilicus is centrally located at the midpoint of the anterior abdominal wall, at the level of the highest points of the iliac crests, opposite the disk between the third and fourth lumbar vertebrae. Despite its innocuous appearance, the umbilicus is an important anatomic and embryologic landmark, transmitting the umbilical vessels and structures related to the digestive and urinary systems during intrauterine life. Most umbilical lesions present with swelling and/or discharge irrespective of the underlying etiology. We undertook a study on surgically excised umbilical lesions, to investigate the spectrum of lesions that occur at this site and to study the histopathology, since the establishment of an accurate tissue diagnosis is essential for definitive treatment. We also reviewed pertinent literature on the embryological basis of the lesions which occur in this region.
| Subjects and Methods|| |
We retrospectively reviewed all the cases of surgically excised umbilical lesions received for histopathology over 12 years (2008–2019) at our tertiary care pediatric hospital. We excluded the cases of Meckel's diverticulum since these are generally received as ileal segments rather than an umbilical polyp/mass and both clinical presentation and management are different in these cases. We studied demographic features including age and sex and noted down the clinical presentation from the records.
We classified the umbilical lesions as “developmental” and “others.” Developmental lesions were further classified as a) defect in the closure of the body wall e.g., omphalocele, omphalitis. b) defect in the closure of the umbilical ring e.g., umbilical hernia c) persistence of embryologic remnants e.g., omphalomesenteric ducts (OMD) remnants or allantoic duct remnants d) failure of epithelialization e.g., umbilical granuloma. We also studied the other lesions at this site including epidermal inclusion cyst or skin tag. The classification scheme followed is shown in [Figure 1].
The cases with embryologic remnants were further subdivided into a) complete patency of the tract e.g., fistula and b) partial patency of the tract e.g., sinus (proximal tract), cyst (middle portion), diverticulum (distal portion) [Figure 2]. We studied the cases showing more than one type of developmental defect.
|Figure 2: Classification of embryonic remnants based on patency of the tract|
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We studied the histology of all the cases. We focused on the OMD remnants to observe the clinical presentation and to identify the different tissue types present.
| Results|| |
During the study period, 71 cases with umbilical lesions were identified. Of these, 49 were male and 22 were female (M:F =2.2:1). The age range was 1 day to 13 years. Sixty-seven cases were developmental. The developmental lesions included 4 cases of omphalocele sacs with dense acute inflammation, 2 cases of umbilical hernia showing only fibrocollagenous tissue, 30 cases of OMD remnants, 10 cases of allantoic duct remnants, 19 cases of umbilical granuloma, and 2 cases showing more than one developmental mechanism [Table 1]. Four cases were classified as “others” including 3 epidermal inclusion cysts, and 1 skin tag.
The demographic features of each group are shown in [Table 2]. A male preponderance was noted in all the subgroups. “Umbilical swelling” was the most common presenting complaint. The clinical features are summarized in [Table 3]. The sub-classification of OMD and allantoic duct remnants are presented in [Table 4]. Sinuses (arising from the distal tract) were found to be more common than cysts involving the middle portion or fistulas involving the entire tract. Correlation or clinical presentation of OMD cases with patency of the tract is presented in [Table 5]. All the fistulas presented with discharge.
|Table 1: Demographics and clinical presentation of cases showing more than one developmental mechanism|
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Histological examination of the OMD remnants showed enteric (small bowel) type mucosa to be the most common, followed by gastric and colonic mucosae [Table 6]. While only colonic mucosa was found in four (4) cases, none of the cases showed the presence of only gastric mucosa. One case showed ectopic pancreatic tissue composed of acini, ducts, and islets of Langerhans.
| Discussion|| |
The development of the umbilicus begins in the fourth week of fetal life as the umbilical ring which forms due to the craniocaudal and lateral infolding of the embryonic disk. The formation of the umbilical ring divides the primitive yolk sac into intracoelomic and extracoelomic portions. The intracoelomic yolk sac develops into the midgut and hindgut. At this point, a broad communication exists between the developing gut and the extracoelomic yolk sac. This communication is narrowed due to differential growth of the anterior body wall and elongation of the intestinal tract to form the vitelline or OMD which is supplied by the vitelline artery and vein. Together, these structures are known as the “yolk stalk.” The “body stalk” comprised of the paired umbilical arteries, umbilical vein, and the allantois; a diverticulum of the hindgut portion of the intracoelomic yolk sac, undergoes fusion with the “yolk stalk” to form the umbilical cord which is invested by a layer of the amniotic membrane.
The OMD obliterates between the fifth and ninth weeks of intrauterine life. This is followed by fibrous obliteration of the allantois between the eighth and sixteenth weeks of gestation to form the urachus or median umbilical ligament. The umbilical arteries and veins close shortly after birth to form the lateral umbilical ligaments and ligamentum teres, respectively. Meckel's diverticulum, a true diverticulum arising from the ileum, is caused by the failure of the obliteration of the most proximal portion of the OMD. It is supplied by the superior mesenteric artery.
The umbilical cord spontaneously separates seven to fifteen days after birth and separation after 3 to 4 weeks is considered to be delayed. The base of the umbilicus heals rapidly following cord separation and becomes covered by squamous epithelium. Most developmental lesions of the umbilicus occur due to defect in the growth of anterior body wall, failure of umbilical ring closure, the persistence of embryological remnants, or inadequate epithelialization of the base. Umbilical lesions occur in about 2% of neonates; however, lesions of greater severity, not responding to topical therapy, and warranting surgical excision are rare and there is no published population incidence of the same.
An omphalocele occurs due to the failure of closure of the anterior body wall or failure of the midgut to return to the abdominal cavity. The abdominal contents are seen lying outside the body, where they are covered by a sac composed of the amnion, Wharton's jelly, and peritoneum [Figure 3]a. Omphaloceles are classified as minor (<5 cm) or major (>5 cm) based on size. Omphaloceles are usually diagnosed antenatally by ultrasound and are often associated with chromosomal and cardiac defects., In these cases, the exposed viscera are kept covered with saline-soaked gauze and definitive surgery for closure of the defect is carried out within hours. Complications can occur prenatally and after surgery including trauma to the liver, hypothermia, and sepsis.
|Figure 3: (a) Omphalocele sac lined by amnion (arrow) with omphalitis (asterisk) (H and E ×100), (b) OMD remnant, type fistula lined by enteric epithelium (H and E ×20), (c) OMD remnant, type sinus lined by colonic epithelium (H and E ×20), (d) OMD remnant, type cyst lined by colonic epithelium (H and E ×20)|
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Omphalitis is defined as erythema and edema of the umbilical ring with or without discharge from the umbilicus. It may be the result of poor hygienic conditions or delays in medical care. Bacterial colonization of the umbilical stump occurs in these cases which can progress to necrotizing fasciitis of the abdominal wall or sepsis. Omphalitis is treated aggressively with parenteral antibiotics effective against both gram-positive cocci and gram-negative rods.,
An umbilical hernia is a common umbilical disorder seen in infants and children which develops when the umbilical ring fails to close after cord separation. The defect is covered by skin anteriorly and peritoneum posteriorly. The diameter of the defect is rarely greater than 2 cm and it is generally painless. Umbilical hernias are common in premature infants, trisomies, and mucopolysaccharidosis., Umbilical hernias usually close spontaneously during the first 3 years of life. Repair is thus, deferred until the age of 4–6 years. Incarceration of the bowel is an uncommon complication and warrants urgent surgical evaluation and repair. Specimens from umbilical hernias are rarely received for histopathological examination.
Complete patency of the OMD produces a communication between the ilium and umbilicus known as a fistula characterized by drainage of enteric contents from the umbilicus [Figure 3]b. Failure of obliteration of the distal portion of the OMD produces a sinus [Figure 3]c while incomplete obliteration of the middle portion leads to the formation of a cyst,, [Figure 3]d. Failure of the obliteration of the proximal portion of the OMD causes Meckel's diverticulum which may or may not be symptomatic. Intestinal obstruction, abdominal pain, and electrolyte imbalance are the complications of Meckel's diverticulum. It is generally treated by resection and anastomosis of the ileum.
Allantoic duct remnants are not common. Failure of obliteration of the allantois leads to abnormalities such as patent allantoic duct (fistula), allantoic sinus, and allantoic cyst. Patency of the tract leads to the discharge of urine through the umbilicus. Such remnants may also lead to infection at the umbilicus,,, [Figure 4]a.
|Figure 4: (a) Allantoic duct remnant, type fistula showing urothelial lining (H and E ×40), (b) Umbilical granuloma (H and E ×20), (c) Developmental lesion showing two mechanisms – gross (left) and microscopy (right) showing minor omphalocele (arrow) and OMD remnant, type fistula lined by enteric epithelium (asterisk) (H and E ×20), (d) OMD remnant, type fistula lined by enteric epithelium (arrowhead), the gastric epithelium (arrow) and pancreatic tissue (asterisk) (H and E ×20) Inset - pancreatic tissue with ducts, acini, and islets (H and E ×400)|
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Cutaneous remnants of the OMD or allantoic duct may produce swelling, discharge, and pain at the umbilicus which does not respond to topical silver nitrate and may need to be excised. Those associated with patent tracts or other anomalies may require probing of the base of the lesion or exploration of the peritoneal cavity. Expert care and management by a pediatric surgeon or pediatric urologist may be needed. Imaging modalities such as ultrasonography or fistulography may be useful.
Umbilical granulomas occur due to late separation of the umbilical cord, incomplete epithelialization over the umbilical ring area, or an inflammatory process. The role of cord clamping techniques in the formation of umbilical granulomas is debatable. It is generally seen as a small mass of tissue measuring 1 mm to 10 mm in diameter with a moist, fleshy, and pink appearance. Microscopically, the umbilical granuloma is a misnomer, being composed of fibroblasts, numerous small blood vessels, and inflammatory cells in an edematous stroma [Figure 4]b. Aggregates of epithelioid histiocytes, a feature of a true granuloma, are not seen. Due to the absence of neural elements, these lesions are devoid of pain., Small umbilical granulomas are treated with applications of topical silver nitrate. Proximal clamping of the umbilical cord within 24 h may be an effective method to prevent the development of umbilical granuloma. Larger granulomas, refractory to silver nitrate may require surgical excision.
Developmental lesions may also occur by more than one mechanism [Figure 4]c. The four major developmental mechanisms, representative lesions, and their corresponding treatment options are summarized in [Table 7]. Other entities including epidermal inclusion cysts, fibroepithelial polyps, and hemangiomas have also been described at the umbilicus., The treatment of these lesions is similar to that at other sites.
|Table 7: Mechanism and treatment of developmental umbilical lesions with examples|
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In our study, half the cases presented in the first year of life and a male preponderance was noted. The most common clinical presentations were umbilical swelling followed by discharge and bleeding. Two cases, which presented with bleeding harbored gastric tissue. The majority (95%) of pediatric umbilical lesions were developmental. In our study, on surgically excised pediatric umbilical lesions, persistent embryologic remnants were most common, possibly because most umbilical granulomas are managed medically. Sinuses (persistence of the distal tract) were most common.
The literature on the histology of OMD remnants is limited. The presence of enteric (small bowel), colonic, gastric, and pancreatic tissue has been described. In our study, enteric mucosa was most common in OMD remnants, a contradiction to other studies. In the present study, we did not find any cases showing purely gastric mucosa. We identified pancreatic tissue composed of acini, ducts, and islets which we classified as Heinrich type 1 [Figure 4]d. Since the stomach and pancreas are essentially foregut derivatives, the presence of these tissues at the umbilicus may result from metaplasia of endodermal tissue or the differentiation of totipotent endodermal cells derived from the gut or OMD.
| Conclusion|| |
To our knowledge, this is the largest series on the histology of pediatric umbilical lesions in the world. Most of the umbilical lesions in our study were developmental. We classified these lesions based on embryology and histology. Our study contributes to the understanding of these rare and poorly studied lesions which may not be familiar to the general surgical pathologist. We hope that the accurate diagnosis of these lesions will lead to improved patient management and better outcomes.
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Conflicts of interest
There are no conflicts of interest.
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Department of Pathology, Bai Jerbai Wadia Hospital for Children, Acharya Donde Marg, Parel, Mumbai - 400 012, Maharashtra
Source of Support: None, Conflict of Interest: None
[Figure 1], [Figure 2], [Figure 3], [Figure 4]
[Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6], [Table 7]