Pathology of the Head and Neck

Neck Cysts, Metastasis, Dissection Chapter 9 267Fig. 9.3. First branchial cleft cyst, Type II. Squamous epitheliumlining the cystic cavity. Note the presence of skin appendage structuresand cartilage in the stromaFig. 9.5. Branchogenic carcinoma. Inset: malignant squamousand respiratory epithelium lining the cystic wallNeither the fifth nor the sixth branchial arch formsclefts or pouches in humans [126]. Branchial cleft cystshave been reported infrequently in the parotid, thyroidand parathyroid glands, floor of the mouth, tonsil,pharynx and mediastinum [17]. Many of these cystshave the microscopic features of lymphoepithelial cysts(Fig. 9.4).9.3.2 Branchiogenic CarcinomaFig. 9.4. Lymphoepithelial cyst. Note the absence of lymphoidhyperplasiathe only effective treatment. In some cases, this may necessitatea superficial parotidectomy. First branchial cleftabnormalities must be differentiated pathologically fromepidermal cysts (especially type I), dermoids (especiallytype II), and cystic sebaceous lymphadenoma.Anomalies from the third and fourth branchial apparatusesare rare and together account for fewer than 5% ofall branchial cysts, sinuses and fistulae [80]. A fistula inthe pyriform sinus is one of the more common manifestationsof a third branchial anomaly [32]. Recurrent infectionsof the lower neck, including suppurative thyroiditis,and a fistulous tract into the pyriform sinus are the featuresof a fourth branchial cleft or pouch anomaly [80].Third and fourth branchial sinus anomalies can bedistinguished only by detailed surgical exploration. Athird branchial sinus always extends from the pyriformsinus through the thyroid membrane cranial to the superiorlaryngeal nerve. In contrast, a fourth branchialsinus extends from the pyriform sinus caudal to the superiorlaryngeal nerve and exits the larynx near the cricothyroidjoint [127].Branchiogenic carcinoma or primary cervical neoplasticcysts are of interest from an historical viewpoint [69,96]. Few of the purported examples of this entity fulfilthe four criteria that Martin et al. considered necessaryto establish the diagnosis, which are as follows:1. The cervical tumour occurs along the line extendingfrom a point just anterior to the tragus, along theanterior border of the sternocleidomastoid muscle, tothe clavicle;2. The histologic appearance must be consistent with anorigin from tissue known to be present in the branchialvestigial;3. No primary source of the carcinoma should be discoveredduring follow-up for at least 5 years;4. Cancer arising in the wall of an epithelium-lined cystsituated in the lateral aspect of the neck can be demonstratedhistologically (Fig. 9.5) [69].The fulfilment of these criteria is practically impossible,and the existence of “ branchiogenic carcinoma” mustremain entirely hypothetical [69, 73, 96, 116]. The criteriahave been criticised on the grounds that they aremuch too restrictive and nearly preclude a diagnosis ofbranchiogenic carcinoma [15, 86].Several authors have estimated that, even acceptingtentative examples of branchiogenic carcinoma, its incidencewould be minuscule (0.3% of all malignant su-