Origins and treatment of cystic lesions in the head and neck region EW Müller Most cystic lesions of the head and neck region are of embryonic origin. They are usually easily diagnosed and rarely need an additional workup. Some of these lesions may not be symptomatic until adulthood or may not be easily recognized. Knowledge of the embryonic origin is essential to successful treatment. Thyroglossal cyst Thyroglossal duct cysts (TDCs) comprise about 70% of congenital neck masses. Embryology: During the 4th to 7th week of embryology, the foramen caecum at the base of the tongue is the site of thyroid development. As the tongue develops, the thyroid diverticulum descends down into the neck, maintaining its connection to the foramen caecum. During descent of the diverticulum, the thyroid develops and the thyroglossal duct atrophies. If parts of the duct fail to involute, a thyroglossal cyst may develop. Secretion of the epithelium lined remnant of the thyroglossal duct (TD) can begin anytime which explains why only 50% of TDCs present before the age of 20yrs. Hyoid development and descent of the thyroid occur simultaneously. The TD can be dorsal, ventral or, most commonly, be embedded in the centre of the hyoid bone. Since the tract never reaches the surface of the skin, thyroglossal fistulas are always acquired, either secondary to surgery or infection. Errors in thyroid descent can result in a lingual thyroid. Ectopic thyroid tissue can be scattered along the whole course of the TD. A pyramidal lobe is found in about 40% due to non resorption of the distal TD. Clinical Presentation and Evaluation 80% of TDCs are found adjacent to the hyoid bone. They have a smooth contour and move with swallowing or with movements of the tongue because they are attached to the hyoid bone. Differentiation from dermoid cysts can be difficult, because they might also be attached to the hyoid. The further differential diagnosis includes ectopic thyroid tissue, thyroid neoplasm, submental lymphadenitis and lipoma. Because of their communication to the base of the tongue via the foramen caecum, the TDCs often become infected, making diagnosis and treatment more difficult. Preoperative ultrasound is an important screening tool to demonstrate a normal thyroid before a suspected TDC is excised. Routine preoperative hormone studies are not necessary if the child appears clinically euthyroid. A thyroid scan is of value if the patient is hypothyroid or the sonar fails to demonstrate a normal thyroid. Treatment Surgical treatment consists of en bloc cystectomy, central hyoidectomy with tract excision up to the foramen caecum. The defect in the geniohyoid and mylohyoid muscles is reapproximated. It is not necessary to close the defect in the hyoid bone (Sistrunk procedure). The operation should be done as soon as possible to avoid an intervening infection. If an infection is already present, this should be treated with antibiotics and an abscess drained if present. Once the inflammation has been cleared, a wide Sistrunk procedure is done excising the distorted edges of the cyst. Recurrent disease is attributed to incomplete resection either of the central part of the hyoid or the central stalk leading to the foramen caecum. It shows usually within a year after primary resection. Clinically it presents as an infection in the region of the previous excision. Unfortunately, the recurrence rate after secondary TDC excision is as high as 25%. Thyroglossal duct papillary carcinoma is not seen in children, but can occur in adults. Controversy exists whether a Sistrunk operation suffices in these cases or if a total thyroidectomy should be added. Anomalies of the Branchial Clefts Branchial anomalies contribute 30% of the congenital neck masses and can present as fistulas, sinuses or cysts. Cysts present later than the other abnormalities. Complete fistulas are more common than sinuses and during childhood both are more common than cysts. Embryology: By the end of the fourth week of gestation, four well defined arches (and two rudimentary arches) have been formed in the lower face and neck region of the embryo. These are lined externally by ectoderm, internally by endoderm, with mesoderm in between. Each arch is separated by clefts externally and pouches internally. In fish these structures form gills, but in humans these clefts and pouches are gradually obliterated to form head and neck structures. Branchial anomalies result from incomplete obliteration of the clefts and pouches. As the embryo grows, the arches coalesce and obliterate all the clefts except for a portion of the first, which becomes the eustachian tube and the auditory canal (Fig. 19-1). The first branchial arch forms the mandible and contributes to the maxillary process of the upper jaw. Abnormal development of this arch results in a wide range of facial deformities, including cleft lip and palate, an abnormal shape or contour of the external ear, and malformed internal ossicles. The second branchial arch forms the palatine tonsil, the tonsillar fossa, and the hyoid bone. The most common branchial abnormalities (90%) arise from the second cleft. These abnormalities are thought to be due to incomplete obliteration as the first arch overgrows the second, third, and fourth clefts and fuses with the lateral branchial wall. The third arch gives rise to the inferior parathyroid glands and the thymus (Fig. 19-1). The fourth branchial arch forms the superior parathyroid glands and the ultimobranchial body, which is responsible for development of the thyrocalcitonin-producing parafollicular cells of the thyroid gland. Anomalies of the third and fourth clefts and pouches are rare. Clinical presentation: Cleft anomalies can present as cysts, sinuses or fistulae. When a sinus is present, the diagnosis is made in childhood. If no external opening exists, the diagnosis might be delayed until adolescence or adulthood. An external sinus is located at the anterior border of the sternocleidomastoideus (SCM) muscle secreting clear mucoid fluid. The diagnosis is often apparent on examination rendering further special examinations unnecessary. Branchial cleft cysts present high in the neck as a palpable lesion deep to the SCM muscle between the bifurcation of the carotid artery. They might be confused with lymphangiomas, haemangiomas, lymphadenopathy and metastatic tumors. Branchial cleft cysts can become secondarily infected and this can be the first sign alerting the physician of its presence. Diagnosis: Sonar is very helpful showing the typical position of these lesions and separating cystic from solid lesions. If necessary further examinations may help (CT, MRI, FNA), especially with solid masses. Treatment: The definitive treatment of these abnormalities is surgical excision. Unresected cysts and sinuses have a high risk for infection. Surgery in infants is delayed until age 3 to 6 months of age to minimize the risk associated with anaesthesia, in older individuals the surgery is done as soon as conveniently possible. As with thyroglossal cysts, acute infections should first be treated with antibiotics, needle aspiration or with incision and drainage followed with complete excision after resolution of the infection. Lymphangiomas Lymphangiomas can arise anywhere in the body, but their preferred site is the head and neck region (50%). They present at birth or in early childhood; 90% are diagnosed before the age of 2 years. Embryology: Lymphangiomas are lymphatic cysts that have become isolated during embryological development and fail to drain into the venous system. Clinical presentation and evaluation: Most lymphangiomas present as a painless cystic mass or diffuse swelling which grows slowly with the child. Upper respiratory tract infections or trauma may enlarge the mass or worsen the swelling. In a few patients this requires intervention to secure the airway. History and physical findings strongly suggest the diagnosis in about half of the patients. In the other cases, it is necessary to differentiate from other cystic lesions occurring in this region. CT and US confirm the cystic nature of the lymphangioma. MRI is best in evaluating the extent and relationship to other structures of the neck. Needle aspiration helps to differentiate lymphangiomas from other fluid filled masses. Types: Lymphangiomas are classified as macrocystic or microcystic. The macrocystic type consists of cysts bigger than 1cm and contains less than 5 cysts; in the microcystic type there are more than 5 cysts and/or they are smaller than 1 cm. Treatment: Two main treatment modalities exist: Surgical excision and injection therapy with sclerosing agents. The different sclerosing agents (Bleomycin, alcohol, tetracycline, etc.) are probably equally efficacious. OK-432, which is a lyophilized extract of Streptococcus pyogenes, is said to cause less perilesional fibrosis than other agents. Injection therapy works well for the macrocystic types, but unfortunately, these types are not very common. Surgery is more efficient in the treatment of lymphangiomas than the sclerosing agents, especially in the microcystic types, but can cause serious complications, especially injuries to important anatomical structures. Treatment: Microcystic lesions should be treated surgically. Macrocystic lesions respond well to sclerosing agents. Lymphangiomas expected to be difficult to excise can be pretreated with sclerosing agents to achieve shrinkage and then excised. Dermoid and Epidermoid Cysts Dermoid and epidermoid cysts result from entrapment of epithelial elements along embryonic lines of fusion and contain endodermal and ectodermal elements. Dermoids are differentiated from epidermoids histologically by the accessory glandular structures found in dermoids. Dermoids contain sebaceous glands, hair follicles and connective tissues. Both contain sebaceous material within the cyst cavity which accumulates with time and causes the cyst to increase in size. The presentation of dermoid cysts is usually typical clinically. The most common location for dermoid cysts in children is along the supraorbital palpebral ridge. This lesion appears as a characteristic swelling in the corner of the eyebrow which moves with the skin. Other locations are in the midline of the neck close to the hyoid. In this case they might move with swallowing or tongue protrusion leading to confusion with thyroglossal duct cysts. They are, however, more superficial and lack a connection with the hyoid bone. Midline scalp lesions should be evaluated for intracranial extension (US, CT, MRI) before excision. Treatment is by complete surgical excision. The rate of recurrence is increased by incomplete resection or intraoperative rupture. References Gross, E., Sichel J. Congenital neck lesions. Surg Clin N Am 86 (2006) 383-392 Acierno, S. P., Waldhausen, J. H. T. , Congenital Cervical Cysts, Sinuses and Fistulae. Otolaryngol Clin N Am 40 (2007) 161 – 176 Organ, G. M., Organ, C. H., Thyroid Gland and Surgery of the Thyroglossal Duct: Exercise in applied Embryology. World J Surg 24 (2000) 886 – 890 Alqahtani, A., Nguyen, L. T. 25 Years’ Experience with lymphangiomas in children. J Pediatr Surg 34 (1999) 1164 – 1168 Okazaki, T., Iwatani, S., Yanai, T. Treatment of lymphangioma in children: our experience of 128 cases. J Pediatr Surg 42 (2007) 386 – 389 Azizkhan, R.,G., DeCou, J. Head and Neck lesions. In Ziegler (Ed), Textbook of Pediatric Surgery, 2006
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