The parents of a 15-day-old boy who returned for his 2-week checkup are worried about a firm, glistening papule on his abdomen that has been present since birth. The patient is otherwise healthy, but the parents are seeking reassurance. A pediatric dermatology referral was quickly placed.
Cutaneous foregut cyst
Clinical and histologic findings
On exam, a healthy, vigorous newborn with a nontender, bluish papule measuring approximately 1.0 cm in diameter located in the midline of his epigastric region was noted. There was no apparent sinus opening or tract around this lesion. Abdominal ultrasound identified a superficial and subcutaneous cyst measuring up to 8 mm with no definite communication with underlying abdominal structures.
Histopathology showed the cyst to be lined by pseudostratified ciliated columnar epithelium. Most of the lining was directly in apposition with fibrous connective tissue, with very few areas of associated smooth muscle noted. No inflammation or cartilage was noted, and the cyst appeared to be localized to the dermal space superficial to the subcutis.
Foregut cysts are formed by abnormal budding during the process of embryonic foregut division to respiratory and intestinal elements at about the fifth week of intrauterine life.1 Most foregut cysts are located in the mediastinum; however, if complete separation and migration occur, they can appear in remote locations such as the skin. These cysts are further broken down into bronchial, esophageal, gastric, and enteric cysts on the basis of microscopic features.
Controversy exists between the labeling of these cysts as foregut versus bronchogenic.2 However, the absence of cartilage and bronchial glands and the presence of smooth muscle excludes the diagnosis of a bronchogenic cyst.3 The ciliated epithelium should not be used to classify these cysts, because this lining may persist postnatally and is variably present in both esophageal and bronchogenic cysts.1
There have been more than 50 reported cases of cutaneous bronchogenic cysts; most do not include the presence of cartilage as a diagnostic requirement. The most common location of the cutaneous bronchogenic cysts is the suprasternal notch followed by the presternal area, neck, and scapula.4
The primary difference between foregut cysts and bronchogenic cysts appears to be the time at which abnormal budding occurs.3 During embryonic development, the primitive foregut arises in the third week of gestation and divides into the dorsal portion, which elongates to form the esophagus, and the ventral portion, which forms the tracheobronchial tree.
The cutaneous location of bronchogenic cysts may result from migration of pinched-off tissue from the thorax to the abdomen, continuing through the midline, before closure of the sternal mesenchymal bars during the seventh week.5,6 This theory may make cutaneous, nonbronchogenic foregut cysts even more of a rarity because the pinching off in foregut cysts occurs at a later time in prenatal development.3
Although rare, cutaneous foregut cysts should be included in the differential diagnosis of congenital cysts and papules/nodules on the anterior abdominal wall. This case may be the first reported foregut cyst to be located completely in the dermis of the abdominal wall.
Evaluation and treatment
With most midline cystic lesions, imaging is recommended to exclude any communication with underlying structures. An ultrasound was sufficient to exclude this finding in our patient; however, further imaging such as magnetic resonance imaging may be indicated if ultrasound is inconclusive.
Bronchogenic cysts have associated complications such as infections, hemorrhage, and rarely malignant transformation. Therefore, in most instances, complete surgical excision is the recommended treatment.7
Our patient underwent surgical excision of the cyst at 4 weeks and has had no complications or recurrences. He was recently seen in the office for a different reason and is doing well.